NL2031897B1

NL2031897B1 - Localized passivated contacts for Solar Cells

Info

Publication number: NL2031897B1
Application number: NL2031897A
Authority: NL
Inventors: Isabella Olindo; Alejandro Procel Moya Paul
Original assignee: Univ Delft Tech
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2023-11-24
Also published as: WO2023224471A1

Abstract

l 9 ABSTRACT The present invention is in the ﬁeld of a semiconductor device sensitive to light, and specially adapted for the conversion of the energy of such radiation into electrical energy, in particular a silicon hetero-junction solar cell, or photovoltaic (PV) cell, a method for the 5 manufacture thereof, and details thereof. Said solar cells comprise at least one hetero junc- tion and typically two hetero junctions.

Description

P100803NL00

Localized passivated contacts for Solar Cells

FIELD OF THE INVENTION

The present invention is in the field of a semiconductor device sensitive to light, and specially adapted for the conversion of the energy of such radiation into electrical energy, in particular a silicon hetero-junction solar cell, or photovoltaic (PV) cell, a method for the manufacture thereof, and details thereof. Said solar cells comprise at least one hetero junc- tion and typically two hetero junctions.

BACKGROUND OF THE INVENTION

A solar cell, or photovoltaic (PV) cell, is an electrical device that converts energy of light, typically sun light (hence “solar™), directly into electricity by the so-called photovoltaic effect. The solar cell may be considered a photoelectric cell, having electrical characteristics, such as current, voltage, resistance, and fill factor, which vary when exposed to light and which vary from type of cell to type.

Solar cells are described as being photovoltaic irrespective of whether the source is sunlight or artificial light. They may also be used as photo detector.

When a solar cell absorbs light it may generate either electron-hole pairs or excitons.

In order to obtain an electrical current charge carriers of opposite types are separated. The separated charge carriers are “extracted” to an external circuit, typically providing a DC-cur- rent. For practical use, a DC-current may be transformed into an AC-current, e.g. by using a transformer. Typically solar cells are grouped into an array of elements. Various elements may form a panel, and various panels may form a system.

Wafer-based c-Si solar cells contribute to more than 90% of the total PV market. Ac- cording to recent predictions, this trend will remain for the upcoming years and many years beyond. Due to their simplified process, conventional c-Si solar cells dominate a large part of the market. As an alternative to the industry to improve the power to cost ratio, the silicon heterojunction approach has become increasingly attractive for the PV industry, even though the relatively complicated process to deploy the proper front layers, such as a transparent conductive oxide (TCO) and an inherent low thermal budget of the cells limiting usage of existing production lines and thus result in a relatively small market share so far. A hetero- junction 1s an interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. A homojunction relates to a semiconductor interface formed by typically two layers of similar semiconductor material, wherein these semiconductor materials have equal band gaps and typically have a different doping (either in concentration, in type, or both). A common example is a homojunction at the interface between an n-type layer and a p-type layer, which is referred to as a p-n junction. In heterojunctions advanced techniques are used to precisely control a deposition thickness of layers involved and to create a lattice-matched abrupt interface. Three types of heterojunctions can be distinguished, a straddling gap, a staggered gap, and a broken gap.

A disadvantage of solar cells is that the conversion per se is not very efficient, typi- cally, for Si-solar cells, limited to somewhat above 20%. Theoretically a single p—n junction crystalline silicon device has a maximum power efficiency of 32%. An infinite number of layers may reach a maximum power efficiency of 86%. The highest ratio achieved for a solar cell per se at present is about 44%. For commercial silicon solar cells, the record is about 26.7% (an interdigitated back-contacted silicon heterojunction solar cell). In view of effi- ciency, the front contacts may be moved to a rear or back side, eliminating shaded areas. In addition, thin silicon films were applied to the wafer. Solar cells also suffer from various im- perfections, such as recombination losses, reflectance losses, heating during use, thermody- namic losses, shadow, internal resistance, such as shunt and series resistance, leakage, etc. A qualification of performance of a solar cell is the fill factor (FF). The fill factor may be de- fined as a ratio of an actual maximum obtainable power to the product of the open-circuit voltage and short-circuit current. It is considered to be a key parameter in evaluating perfor- mance. A typical advanced commercial solar cell has a fill factor > 0.75, whereas less ad- vanced cells have a fill factor between 0.4 and 0.7. Cells with a high fill factor typically have a low equivalent series resistance and a high equivalent shunt resistance; in other words, less internal losses occur. Efficiency is nevertheless improving gradually, so every relatively small improvement is welcomed and of significant importance.

At present a solar cell having a full area front passivating contact is not attractive, such as due to highly absorptive materials used to build such a structure. That is the case of heav- ily doped poly-silicon and a-Si layers. In a poly-silicon case, the process requires a very thin polysilicon film for minimizing parasitic absorption loss, and in case of a-Si, the process re- quires e.g. an extra transparent conductive oxide (TCO) layer for supporting the carrier lat- eral transport.

In particular, the electron transport layer and/or hole transport layer hinder the conver- sion of light into electrical power. In addition, to form such a transport layer, typically extra process steps in the manufacture of a solar cell are involved, such as a doping step, and the deposition of the transport layer, and possibly even (intermediate) cleaning steps, as well as extra or multi-chamber process tools, typically deposition tools. In view of cross-contamina- tion between tools, it is typically better to use separate tools and/or multi-chamber tools. Ex- tra tools or multi-chamber tools in addition add to the cost of production as more of the ex- pensive clean-room surface is occupied thereby.

Solar cells deliver power electricity from sun light. It is noted that the efficiency of this

PV-process usually 1s limited by material properties and the amount of light arriving to the absorber bulk. Normally, for low temperature processing of high efficiency solar cells, light management is limited by parasitic absorption of the light in front and rear layers. The reason for such parasitic absorption is that collecting layers are designed to cover bulk inter- faces, to support the collection of charge. Indeed, such layers collect efficiently the charge inside the solar cell in spite of limiting the amount of absorbed light in the absorber bulk.

Moreover, such collecting layers use materials that are not abundant in earth, such as indium.

The present invention relates to an improved hetero junction solar cell and various as- pects thereof and a simplified process for manufacturing the solar cell which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates in a first aspect to a solar cell, in particular a het- ero-junction silicon solar cell according, typically a front and rear contacted solar cell, and in a second aspect to a method for making such a solar cell. In this invention, a design of solar cells is provided using localized layers to collect efficiently the charge, and allowing the light to freely arrive to the light absorbing bulk. Furthermore, the present solar cells make use of collecting layers localized in a fraction of the bulk interface, with a reduction of the parasitic absorption. Additionally, it is an option to reduce the use of materials during the manufacture of the solar cells. In particular, the light collecting layers use materials that are not abundant in earth, such as indium. Inventors present a design of solar cells using local- ized layers to collect efficiently the charge and allowing the light to freely arrive to the ab- sorber bulk. Furthermore, as the proposed design devise the use of collecting layers are lo- calized to a small part of the bulk interface, it is a clear option to reduce and eventually avoid the consumption of materials during the processing. The present invention is in particular feasible with photovoltaic industry based in low temperature process for Silicon solar cells.

The invention involves the removal of a substantial part of the transparent conductive oxide (TCO) layer, in particular both the front and rear side TCO layer. More in particular the part of the TCO layer which is not underneath a contact or contact layer is removed. “Re- moval” is in view of typical prior art solar cells, which have a full TCO-layer. In the present invention the TCO needs only to be provided underneath the respective contact. A full TCO- layer can be provided, and then mostly removed, such as by etching. The removed TCO can be reused. Or, a mask or the like can be used to provide the TCO layer only partially on the surface available, and not on the surface occupied by the exemplary mask. Therewith, from the beginning less TCO-material is used. Also the performance of the obtained solar cell is comparable to prior art solar cells, albeit less material is used. In addition to the substantial absence of the TCO also the doped silicon layer may be likewise substantially absent. In ad- dition, the TCO can be made even thinner. Therewith also less dopants are to be used. A proof-of-concept SHJ solar cell exhibits a VOC of >700 mV, a JSC of about 40 mA/cm?, a

FF of >80%, and an efficiency of >23%.

So due to the substantial removal of the TCO and optional doped silicon layers in the prior art structure of SHJ solar cells, the present invention clearly allows a simpler process,

cost reductions, and material savings. Cost reductions come from both materials saving dur- ing the device manufacturing, and also simplification of fabrication tools, in particular the

Plasma-Enhanced Chemical-Vapor-Deposition (PECVD). This invention is furthermore in- dustrial relevant due to minimal use of scarcely available materials, such as In.

In the prior art, optimization of the design of low temperature processed solar cell are twofold: 1) enhancing vertical transport of charge and ii) enhancing lateral transport of charge. It is well-known that lateral transport of charge is supported by collecting layers.

However, the present solar cell makes use of such layers in a localized part of the interface.

It enables more light to arrive inside the bulk. Therefore, the present inventive concept is dif- ferent or even contrary to the common vision in the photovoltaic research. Typically the PV- research community is focusing efforts e.g. on achieving ultra-thin collecting layers to re- duce the parasitic absorption in solar cells. This layers are typically still covering the com- plete absorbing bulk interface. Therefore, achieving such a level of minimized parasitic ab- sorption is challenging from a processing point of view. On the contrary, the present inven- tors provide this layer localized only beneath metal contacts. Accordingly, it allows some flexibility regarding processing, for instance the thickness of collecting layers that has less impact in the illuminated area. The present invention is therefore better than available alter- natives, as it uses less material and allows more flexibility in the manufacture of a solar cell.

Indeed, thanks to the present invention, the use of ultra-thin layers is no longer a limitation for improving the performance of high efficiency solar cells. For implementing this inven- tion the use of hard masks and its alignment is considered. The impact of the present inven- tion may be expressed in terms of less material consumption and the provision of more effi- cient solar cells, such as with a higher charge current density.

In the present solar cells either front and rear (also indicated as back) contacts, or both, may be present. The present solar cell comprises at least one hetero junction and typically two hetero junctions. The heterojunctions may be of staggered type. The present solar cells comprise a substrate (10), wherein the substrate typically comprises Si and dopants, directly on the substrate, at least one intrinsic layer (11), directly on the intrinsic layer a doped silicon layer, which may or may not occupy the full surface area of the intrinsic layer, and on the doped silicon layer a transparent conductive oxide (TCO)-layer (12), which may or may not occupy the full surface area of the doped silicon layer. The doped silicon layer may function as electron transport layer [ETL], or as hole transport layer [HTL], respectively. Also the transparent conductive oxide (TCO)-layer (12) provides electron transport or hole transport, respectively, and a metal contact (15) in electrical contact with the TCO-layer. The substrate is typically a crystalline Si-substrate, such as a n-doped or p-doped crystalline Si layer 10, typically of 50 um-300 um thickness. The layers of the stack are typically provided directly on one and another, that is, without an intermediate layer, or in any case an intermediate layer of significance to the performance of the hetero junction solar cell.

In a second aspect the present invention relates to a method of producing a front-side and back-side contacted silicon hetero-junction solar cell (100) according to the invention, comprising providing a substrate, such as a crystalline Si-substrate, optionally texturing the substrate, such as double-side texturing the substrate, thereafter immersing the substrate into 5 a strong oxidizing solution, thereafter etching the oxidized substrate by dipping the oxidized substrate into an acidic solution, directly thereafter loading the etched substrate into a layer deposition tool, and depositing an intrinsic Si layer on at least one side of the etched sub- strate, thereafter providing at least one doped silicon layer on the at least one intrinsic Si- layer, in particular a layer that covers less than 20% of the front surface area or back surface area, respectively, thereafter depositing a transparent conductive oxide(TCO) layer on the at least one doped Si-layer, in particular after a first alignment of the solar cell, and then depos- iting metal contacts on the TCO-layer, in particular after a second alignment of the solar cell, more in particular wherein the first and second alignment each individually is with an accu- racy of better than 20 um lateral, such as better than 1 um lateral.

In summary, the present invention provides a simplified fabrication process wherein solar cell precursors can be finished within a couple of steps, and which is a low cost and high throughput process, using compatible industrial standard metalliza- tion steps, solar cells featuring a high Voc, solar cells featuring a high Jsc & Voc, so- lar cells featuring a relatively high fill factor (FF), and wherein the design is applica- ble to both a front/rear contacted conventional solar cell architecture, a bifacial solar cell architecture, for interdigitated back-contacted (IBC) solar cells, and for both n- type and p-type bulk material.

Thereby the present invention provides a solution to one or more of the above men- tioned problems.

Advantages of the present description are detailed throughout the description. Refer- ences to the figures are not limiting, and are only intended to guide the person skilled in the art through details of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a silicon solar cell, and in a sec- ond aspect to a process for making such a solar cell.

Where multiple layers or the like of a similar or same material are present, characteris- tics of said layers apply to each layer individually. Also “bottom” and “top”, or “front” and “back” are relative terms, which terms may be interchanged in so far as applicable.

In an exemplary embodiment of the present solar cell the substrate is covered with at least one intrinsic layer 11, such as one intrinsic layer at the rear side, and one intrinsic layer at the front side, in particular wherein the at least one intrinsic layer 11 each individu- ally is selected from intrinsic Si, such as (i)a-Si:H and (i)nc-Si:H, from intrinsic Si-dielec- trics, such as (1)a-SiOx:H, (1)a-SiCx:H, and (i)a-SiNx:H, or dielectric metal oxide passivation layer, and combinations thereof.

In an exemplary embodiment of the present solar cell the thickness of the intrinsic layer each individually is from 0.1 nm-50 nm, in particular 1-20 nm, such as 2-15 nm.

In an exemplary embodiment of the present solar cell the intrinsic layer each indi- vidually is textured, in particular with a same texturing as the substrate.

In an exemplary embodiment the present solar cell comprises at least one doped silicon layer 13,14, such as a p-doped silicon layer 13, and an n-doped silicon layer 14, in particular comprising a 5*10H-0.5*101° dopants/cm® n- or p-type doped crystalline Si layer 13,14, and/or wherein a doping concentration is preferably spatially constant.

In an exemplary embodiment of the present solar cell n-type dopants are selected from P, As, Bi, Sb and Li, and wherein p-type dopants are selected from B, Ga, and In.

In an exemplary embodiment of the present solar cell the doped silicon layer is provided in between the at least one contact and substrate.

In an exemplary embodiment of the present solar cell the doped silicon layer sub- stantially covers the same surface area and the same amount of surface area as the at least one contact.

In an exemplary embodiment of the present solar cell the at least one contact is provided on a TCO layer 12, in particular wherein the material of the transparent conductive layer 12 is selected from Indium Tin Oxide (ITO), IOH, ZnO, or doped ZnO, such as Alu- minium doped ZnO, doped Tin oxide, such as fluorine doped tin oxide, doped indium oxide, such as Indium Fluor Oxide (IFO:H), and Indium Tungsten Oxide (TWO).

In an exemplary embodiment of the present solar cell a thickness of the transparent conductive layer 12 is 10-200 nm, in particular 20-170 nm, more in particular 30-50 nm.

In an exemplary embodiment of the present solar cell the refractive index of the transparent conductive layer 12 is <2.2.

In an exemplary embodiment of the present solar cell the work function of the

TCO layer 12 is from 2 eV to 8 eV, in particular 3.4 eV to 6.4 eV.

In an exemplary embodiment of the present solar cell the work function of the

TCO layer 12 is 3.4 eV to 4.7 eV in case of the TCO-layer mainly transporting electrons.

In an exemplary embodiment of the present solar cell the work function of the

TCO layer 12 is 4.7 eV to 6.4 eV in case of the TCO-layer mainly collecting holes.

In an exemplary embodiment of the present solar cell the TCO layer each individu- ally is textured, in particular with a same texturing as the substrate.

In an exemplary embodiment of the present solar cell the contact, in particular a metal contact, more in particular a contact layer, the TCO layer, and optionally the doped sil- icon layer form a stack, in particular a stack of substantially the same shaped layers, more in particular wherein a width of the doped silicon layer (HTL or ETL) > a width of the TCO layer, which width of the TCO layer > width of the contact layer. The width of an underlying layer may be slightly larger than the width of the layer directly on top thereof, such as 1-10% wider, such as 2-5% wider. The respective widths in the stack, or in general of layers on top of one and another, may therefore have substantially the same width.

In an exemplary embodiment of the present solar cell the at least one contact is 5 provided as a strip, in particular at least one of a circular shaped strip, a multigonal shaped strip, a rectangular strip, and a spiral shaped strip, more in particular as a strip with a width of 0.01-200 um, in particular a width of 0.05-50 um, such as 1-5 um.

In an exemplary embodiment of the present solar cell the at least one light ab- sorbing layer is surface treated, in particular wherein the treatment is selected from treatment with a gas, and treatment with a plasma, more particular wherein in the treatment hydrogen is used, or wherein CO: is used, or wherein in the treatment oxygen is used, even more in particular wherein substantially only hydrogen is used, or wherein substantially only oxygen is used. In an example a pressure of 1.1 to 4.4 mbar, a power of 55-90 mW/cm?, and a tem- perature of 160-200 °C may be used, each individually. Preferred values are a pressure of 2.0-2.2 mbar, a power of 80-90 mW/cm?, and a temperature of 180-185 °C. The surface treatment is aimed at changing the surface of the layer, in particular of the doped silicon layer or the intrinsic silicon layer respectively. It provides a better condition/passivation of the absorber bulk. And also it provides a better interface for the application of ARC layer (s)

In an exemplary embodiment of the present solar cell the substrate 10 is a single sided or double sided flat substrate 10 surface.

In an exemplary embodiment of the present solar cell the substrate 10 is a single sided or double sided textured substrate 10 surface (ISO 4287:1997), in particular textured with a surface roughness R, of 1-20 um, such as 2-10 um.

In an exemplary embodiment of the present solar cell the textured surface has an aspect ratio (height:depth of a textured structure) of 2-10.

In an exemplary embodiment of the present solar cell the substrate has a thickness of 1-500 um.

In an exemplary embodiment of the present solar cell comprising 10-1017 do- pants/cm? n- or p-type doped substrate 10.

In an exemplary embodiment of the present solar cell the substrate 10 comprises 1*10'2-1.0*10*! n- or p-type dopants/cm®, in particular 2*10*-10'* dopants/cm’, more in particular 5*10!+-101° dopants/cm?, such as 8*10!*-3*1015 dopants/cm®.

In an exemplary embodiment of the present solar cell the substrate 10 has a resis- tivity of 0.1-1000 ohm*cm at 300K, more in particular 1-100 ohm*cm, such as 5-10 ohm*cm.

In an exemplary embodiment of the present solar cell the at least one contact co- vers less than 5% of the front surface area or back surface area, in particular wherein the at least one contact covers less than 1% of the front surface area or back surface area, more in particular less than 0.5%.

In an exemplary embodiment of the present solar cell the contact comprises a metal, wherein the metal of the contacts independently comprises at least one of Cu, Al, W,

Ti, Ni, Cr, Ag.

In an exemplary embodiment of the present solar cell a thickness of said metal con- tacts 13 is 200 nm-50 pm, in particular 1-25 um.

In an exemplary embodiment of the present solar cell the metal contact 13 is se- lected from a metal layer, a metal grid, a metal line, or a combination thereof.

In an exemplary embodiment of the present solar cell at least one of the front sur- face and the back surface is provided with an anti-reflective coating 16, in particular an anti- reflective coating 16 on the surface area not covered by the contact.

In an exemplary embodiment of the present solar cell the layer underneath the anti- reflective coating is surface treated 17, such as surface treated with Ho, with O2, or a combi- nation thereof. Optionally further chemical species may be present, either reactive species, or inactive species, such as nitrogen, or He.

In an exemplary embodiment of the present solar cell the Voc is >700 mV, in par- ticular > 725 mV, such as > 730 mV.

In an exemplary embodiment of the present solar cell a Js is > 30 mA/cm?, in par- ticular > 38 mA/cm?, such as > 39 mA/cm?.

In an exemplary embodiment of the present solar cell a fill factor (FF) of >75%, in particular > 80%, such as > 82.5%.

In an exemplary embodiment the present solar cell has an efficiency of > 23%, in particular >23 8%, such as > 23.9%.

In an exemplary embodiment of the present solar cell the solar cell is a back-con- tacted solar cell, such as an interdigitated back-contacted solar cell, or wherein the solar cell is a back and front contacted solar cell.

In an exemplary embodiment of the present method deposition of the TCO-layer and/or the metal contacts and optionally provision of the doped silicon layer a hard mask is used. For forming a plurality of solar cells these are typically provided in a tray or pod. Such a tray may house tens of waters. These wafers are then subsequently treated through various process steps, such as deposition of a layer. For PECVD deposition a metal sheet could be used, considered to be a hard mask. The hard mask is carefully aligned with the wafer, or likewise, the solar cell being formed in the relevant process step. For alignment, at least one alignment marker may be used, and typically four markers are used. Using optical means the mask and the wafer can be aligned precisely, typically with an accuracy of 20 um or better, and using advance optical techniques an accuracy of 1 um or even 100 nm can be obtained relatively easy. It is noted that such an accuracy is (more) than sufficient. The hard mask may be provided with ad-hoc engineered, laser-cut openings, which openings provided deposition of the relevant layer on the relevant part of the surface area, and prevent deposi- tion elsewhere, such as with the present contact layer, with the present TCO layer, and op- tionally with the present doped layer. The mask can be cleaned regularly such that the depos- ited material on the mask can be recovered, and reused. As such these localized layers (doped lines, TCO lines, and metal lines) could be deposited, among other techniques, also via hard mask.

In an exemplary embodiment of the present method contacts and/or contact layers are provided by metal deposition and lift off of non-contact areas, screen printing, and elec- trical plating.

The present invention therefore relates to a silicon hetero-junction solar cell (100) as claimed and/or obtained by the method as claimed, comprising at least two elements as men- tioned in the claims, and/or comprising at least one further element as mentioned in the de- scription.

The invention 1s further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being ob- vious or not, may be conceivable falling within the scope of protection, defined by the present claims.

SUMMARY OF FIGURES

Figure 14,b shows an example of a prior-art solar cell.

Figures 2a,b-3a,b show a schematic representation of an example of the present solar cell.

Fig. 4 shows experimental results.

DETAILED DESCRIPTION OF FIGURES

In the figures : 100 hetero-junctions Si-solar cell 10 Si-substrate, typically crystalline, 11 intrinsic silicon layer 12 transparent conductive oxide layer 13 p-doped silicon layer 14 n-doped silicon layer 15 contacts or contact layer 16 anti-reflective coating layer 17 surface treated layer

Various exemplary embodiments of the present solar cell are detailed below.

The solar cell of fig. 1 relates to a prior art solar cell. Fig. 1a shows a typical cross-section comprising a crystalline silicon substrate 10, on both sides thereof an in- trinsic a-Si:H layer 11, a p-doped 13 or n-doped layer 14 on the intrinsic layer,

respectively, a TCO layer 12 covering the doped layer, and metal contacts 15 on the

TCO-layer. Fig. 1b shows a perspective view of the top layers. The bottom layers are formed likewise.

The solar cells of figs. 2-3 relate to the present inventive solar cell. Fig. 2a shows a typical cross-section comprising a crystalline silicon substrate 10, on both sides thereof an intrinsic a-Si:H layer 11, a p-doped 13 or n-doped layer 14 on the in- trinsic layer, respectively, a TCO layer 12 only partially covering the doped layer, and metal contacts 15 on the TCO-layer. Fig. 2b shows a perspective view of the top lay- ers. The bottom layers are formed likewise. Optionally an anti-reflective coating 16 may be present. Before providing the ARC-layer the underlying layer, in this case the intrinsic layer, may be surface treated 17.

Fig. 3a shows a typical cross-section comprising a crystalline silicon substrate 10, on both sides thereof an intrinsic a-Si:H layer 11, a p-doped 13 or n-doped layer 14 only partially provided on the intrinsic layer, respectively, a TCO layer 12 only partially covering the doped layer, and metal contacts 15 on the TCO-layer. Fig. 2b shows a perspective view of the top layers. The bottom layers are formed likewise.

Optionally an anti-reflective coating 16 may be present. Before providing the ARC- layer the underlying layer, in this case the intrinsic layer, may be surface treated 17.

The above types of solar cell are indicative of the versatile design of the present invention.

Jse (mA/cm?) Voe (V) FF(-) n(%)

Baseline (Fig. 1) 39.54 0.732 0.851 24.64

W/O TCO (Fig. 2) 39.59 0.732 0.828 23.98

W/O TCO&doped layer(Fig. 3) 39.94 0.733 0.836 24 45

So for the Js a slightly higher Js for solar cells W/O front layers is obtained.

The difference can be more apparent when working with an ARC. For the Vo no changes are found with respect to a baseline solar cell. For the fill factor (FF) the baseline device has a higher FF, which is considered due to more surface for the cur- rent of collecting carriers. However, the present solar cell structures are more sensitive to interface transport. For the efficiency n almost the same n is found. It is noted that there is a trade-off of FF and Jsc for new devices.

The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying figures.

It should be appreciated that for commercial application it may be preferable to use one or more variations of the present system, which would similar be to the ones disclosed in the present application and are within the spirit of the invention.

For the purpose of searching the next section is added, of which the subsequent section represents a translation into Dutch.

1. A solar cell (100), in particular a heterojunction solar cell, comprising a substrate (10), in particular wherein the substrate comprises silicon, more in particu- lar crystalline Si, at least one P-N junction, in particular a hetero junction, and at least one contact (15) selected from a front contact and a back contact, characterized in that the at least one contact covers less than 20% of the front surface area or back surface area, respectively, and wherein a remainder of the front surface area or back surface area provides access to at least one light absorbing layer and is substantially free of other layers. 2. The solar cell according to embodiment 1, wherein the substrate is covered with at least one intrinsic layer (11), such as one intrinsic layer at the rear side, and one intrinsic layer at the front side, in particular wherein the at least one intrinsic layer (11) each individually is selected from intrinsic St, such as (i)a-Si:H and (i)nc-Si:H, from intrinsic Si-dielectrics, such as (i)a-

Si0«:H, (1)a-SiCx:H, and (1)a-SiNx:H, or dielectric metal oxide passivation layer, and combi- nations thereof, and/or wherein the thickness of the intrinsic layer each individually is from 0.1 nm-50 nm, in partic- ular 1-20 nm, such as 2-15 nm, and/or wherein the intrinsic layer each individually is textured, in particular with a same texturing as the substrate. 3. The solar cell according to any of embodiments 1-2, comprising at least one doped silicon layer (13,14), such as a p-doped silicon layer (13), and an n-doped silicon layer (14), in par- ticular comprising a 5*10!7-0.5* 10?! dopants/cm® n- or p-type doped crystalline Si layer (13,14), and/or wherein a doping concentration is preferably spatially constant, and/or wherein n-type dopants are selected from P, As, Bi, Sb and Li, and wherein p-type dopants are selected from B, Ga, and In. 4. The solar cell according to embodiment 3, wherein the doped silicon layer is provided in between the at least one contact and substrate, and/or wherein the doped silicon layer sub- stantially covers the same surface area and the same amount of surface area as the at least one contact. 5. The solar cell according to any of embodiments 1-4, wherein the at least one contact is provided on a TCO layer (12), in particular wherein the material of the transparent conduc- tive layer (12) is selected from Indium Tin Oxide (ITO), IOH, ZnO, or doped ZnO, such as

Aluminium doped ZnO, doped Tin oxide, such as fluorine doped tin oxide, doped indium oxide, such as Indium Fluor Oxide (IFO:H), and Indium Tungsten Oxide (IWO), and/or wherein a thickness of the transparent conductive layer (12) is 10-200 nm, in particular 20-

170 nm, more in particular 30-50 nm, and/or wherein the refractive index of the transparent conductive layer (12) is <2.2, and/or wherein the work function of the TCO layer (12) is from 2 eV to 8 eV, in particular 3.4 eV to 6.4 eV, and/or wherein the work function of the TCO layer (12) is 3.4 eV to 4.7 eV in case of the TCO- layer mainly transporting electrons, and/or wherein the work function of the TCO layer (12) is 4.7 eV to 6.4 eV in case of the TCO- layer mainly collecting holes, and/or wherein the TCO layer each individually is textured, in particular with a same texturing as the substrate. 6. The solar cell according to embodiment 5, wherein the contact, in particular a metal con- tact, more in particular a contact layer, the TCO layer, and optionally the doped silicon layer form a stack, in particular a stack of substantially the same shaped layers, more in particular wherein a width of the doped silicon layer > a width of the TCO layer, which width of the

TCO layer > width of the contact layer. 7. The solar cell according to any of embodiments 1-6, wherein the at least one contact is provided as a strip, more in particular as a strip with a width of 0.01-200 um, in particular a width of 0.05-50 pm. 8. The solar cell according to embodiment 7, wherein the at least one light absorbing layer is surface treated, in particular wherein the treatment is selected from treatment with a gas, and treatment with a plasma, more particular wherein in the treatment hydrogen is used, or wherein in the treatment oxygen is used, even more in particular wherein substantially only hydrogen 1s used, or wherein substantially only oxygen is used. 9. The solar cell according to any of embodiments 1-8, wherein the substrate (10) is a single sided or double sided flat substrate (10) surface, and/or wherein the substrate (10) is a single sided or double sided textured substrate (10) surface (ISO 4287:1997), in particular textured with a surface roughness R, of 1-20 um, such as 2- 10 um, and/or wherein the textured surface has an aspect ratio (height:depth of a textured structure) of 2- 10. 10. The solar cell according to any of embodiments 1-9, wherein the substrate has a thick- ness of 1-500 um, and/or comprising 10'¥-10*! dopants/cm® n- or p-type doped substrate (10), and/or wherein the substrate (10) comprises 1*10'2-0.5%10!" n- or p-type dopants/cm®, in particular 2*10"-10'7 dopants/cm®, more in particular 5¥10'-10'° dopants/em?, such as 8*101-3*10 dopants/cm?, and/or wherein the substrate (10) has a resistivity of 0.1-1000 ohm*cm at 300K, more in particular 1-100 ohm*cm, such as 5-10 ohm*cm.

11. The solar cell according to any of embodiments 1-10, wherein the at least one contact co- vers less than 5% of the front surface area or back surface area, in particular wherein the at least one contact covers less than 1% of the front surface area or back surface area, more in particular less than 0.5%, and/or wherein the contact comprises a metal, wherein the metal of the contacts independently com- prises at least one of Cu, Al, W, Ti, Ni, Cr, Ag, and/or wherein a thickness of said metal contacts (13) is 200 nm-50 um, in particular 1-25 um, and/or wherein the metal contact (13) is selected from a metal layer, a metal grid, a metal line, or a combination thereof. 12. The solar cell according to any of embodiments 1-11, wherein at least one of the front surface and the back surface is provided with an anti-reflective coating (16), in particular an anti-reflective coating (16) on the surface area not covered by the contact. 13. The solar cell according to embodiment 12, wherein the layer underneath the anti-reflec- tive coating is surface treated (17), such as surface treated with Ho, with O», or a combina- tion thereof. 14. The solar cell according to any of embodiments 1-13, wherein the VOC is >700 mV, in particular > 725 mV, such as > 730 mV, and/or wherein a J is > 30 mA/cm?, in particular > 38 mA/cm?, such as > 39 mA/cm?, and/or a fill factor (FF) of >75%, in particular > 80%, such as > 82.5%, and/or having an efficiency of > 23%, in particular >23.8%, such as > 23.9%. 15. The silicon hetero-junction solar cell (100) according to any of embodiments 1-14, wherein the solar cell is a back-contacted solar cell, such as an interdigitated back-contacted solar cell, or wherein the solar cell is a back and front contacted solar cell. 16. Method of producing a front-side and back-side contacted silicon hetero-junction solar cell (100) according to any of embodiments 1-15, comprising providing a substrate, such as a crystalline Si-substrate, optionally texturing the substrate, such as double-side texturing the substrate, thereafter immersing the substrate into a strong oxidizing solution, thereafter etching the oxi- dized substrate by dipping the oxidized substrate into an acidic solution, directly thereafter loading the etched substrate into a layer deposition tool, and depositing an intrinsic Si layer on at least one side of the etched substrate, thereafter providing at least one doped silicon layer on the at least one intrinsic Si-layer, in particular a layer that covers less than 20% of the front surface area or back surface area, re- spectively, thereafter depositing a transparent conductive oxide(TCO) layer on the at least one doped Si- layer, in particular after a first alignment of the solar cell, and then depositing metal contacts on the TCO-layer, in particular after a second alignment of the solar cell, more in particular wherein the first and second alignment each individually is with an accu- racy of better than 20 um lateral, such as better than 1 um lateral.

17. Method according to embodiment 16, wherein deposition of the TCO-layer and/or the metal contacts and optionally provision of the doped silicon layer a hard mask is used, and/or wherein contacts and/or contact layers are provided by metal deposition and lift off of non- contact areas, screen printing, and electrical plating.

18. Silicon hetero-junction solar cell (100) according to any of embodiments 1-15 and/or ob-

tained by the method according to embodiment 16 or 17, comprising at least two elements as mentioned in the embodiments, and/or comprising at least one further element as mentioned in the description.

Claims

ConclusiesConclusions

1. Een zonnecel (100), in het bijzonder een heterojunctie zonnecel, omvattend een substraat (10), in het bijzonder waarbij het substraat omvat silicium, meer in het bijzonder kristallijn Si, ten minste één P-N junctie, in het bijzonder een hetero junctie, en ten minste één contact (15) gekozen uit een voorcontact en een achtercontact, gekenmerkt door het feit dat het ten minste één contact minder dan 20% van respectievelijk het voorvlak of het ach- tervlak beslaat, en waarbij een rest van het voorvlak of achtervlak toegang verschaft tot ten minste één lichtabsorberende laag en nagenoeg vrij is van andere lagen.1. A solar cell (100), in particular a heterojunction solar cell, comprising a substrate (10), in particular wherein the substrate comprises silicon, more in particular crystalline Si, at least one P-N junction, in particular a hetero junction , and at least one contact (15) selected from a front contact and a rear contact, characterized by the fact that the at least one contact covers less than 20% of the front surface or the rear surface respectively, and a remainder of the front surface or rear surface provides access to at least one light-absorbing layer and is substantially free of other layers.

2. De zonnecel volgens conclusie 1, waarbij het substraat bedekt is met ten minste één intrin- sieke laag (11), zoals één intrinsieke laag aan de achterzijde, en één intrinsieke laag aan de voorzijde, in het bijzonder waarbij de ten minste één intrinsieke laag (11) elk afzonderlijk is gekozen uit intrinsiek Si, zoals (i)a-Si:H en (1)nc-Si:H, uit intrinsieke Si-diëlektrische materialen, zo- als (1)a-S10x:H, (1)a-SiCx:H, en (1)a-SiNx:H, of diëlektrische metaaloxidepassivatielaag, en combinaties daarvan, en/of waar de dikte van de intrinsieke laag elk afzonderlijk van 0,1 nm-50 nm is, in het bijzonder 1-20 nm, zoals 2-15 nm, en/of waarbij de intrinsieke laag elk afzonderlijk getextureerd is, in het bijzonder met dezelfde tex- tuering als het substraat.The solar cell according to claim 1, wherein the substrate is covered with at least one intrinsic layer (11), such as one intrinsic layer on the back, and one intrinsic layer on the front, in particular where the at least one intrinsic layer (11) each individually selected from intrinsic Si, such as (i)a-Si:H and (1)nc-Si:H, from intrinsic Si dielectric materials, such as (1)a-S10x:H, (1)a-SiCx:H, and (1)a-SiNx:H, or dielectric metal oxide passivation layer, and combinations thereof, and/or where the thickness of the intrinsic layer is each individually from 0.1 nm-50 nm, in in particular 1-20 nm, such as 2-15 nm, and/or wherein the intrinsic layer is each individually textured, in particular with the same texture as the substrate.

3. De zonnecel volgens een van de conclusies 1-2, met ten minste een gedoteerde silicium- laag (13,14), zoals een p-gedoteerde siliciumlaag (13), en een n-gedoteerde siliciumlaag (14), in het bijzonder omvattend een 5*101#-0,5* 10?! doteringsstoffen/em’ n- of p-type gedo- teerde kristallijne siliciumlaag (13,14), en/of waarin een doteringsconcentratie bij voorkeur ruimtelijk constant is, en/of waarbij de n-type doteringsstoffen zijn gekozen uit P, As, Bi, Sb, en Li, en waarbij de p-type doteringsstoffen zijn gekozen uit B, Ga, en In.The solar cell according to any one of claims 1-2, with at least one doped silicon layer (13, 14), such as a p-doped silicon layer (13), and an n-doped silicon layer (14), in particular comprising a 5*101#-0.5* 10?! dopants/em' n- or p-type doped crystalline silicon layer (13,14), and/or wherein a doping concentration is preferably spatially constant, and/or wherein the n-type dopants are selected from P, As, Bi , Sb, and Li, and wherein the p-type dopants are selected from B, Ga, and In.

4. De zonnecel volgens conclusie 3, waarbij de gedoteerde siliciumlaag tussen het contact en het substraat is aangebracht, en/of waarbij de gedoteerde siliciumlaag in wezen hetzelfde op- pervlak en dezelfde hoeveelheid oppervlak beslaat als het contact.The solar cell according to claim 3, wherein the doped silicon layer is arranged between the contact and the substrate, and/or wherein the doped silicon layer covers essentially the same area and the same amount of surface area as the contact.

5. De zonnecel volgens een van de conclusies 1-4, waarbij het ten minste één contact is aan- gebracht op een TCO-laag (12), in het bijzonder waarbij het materiaal van de transparante geleidende laag (12) is gekozen uit Indium Tin Oxide (ITO), IOH, ZnO, of gedoteerd ZnO, zoals aluminium gedoteerd ZnO, gedoteerd Tin-Oxide, zoals fluor gedoteerd Tin-Oxide, ge- doteerd indium-Oxide, zoals Indium Fluor Oxide (IFO:H), en Indium Wolfraam Oxide (IWO), en/of waar een dikte van de transparante geleidende laag (12) 10-200 nm is, in het bijzonder 20- 170 nm, meer in het bijzonder 30-50 nm, en/of waarin de brekingsindex van de transparante geleidende laag (12) <2.2 is, en/of waarbij de werkfunctie van de TCO-laag (12) van 2 eV tot 8 eV is, in het bijzonder 3,4 eV tot 6,4 eV, en/of waarin de werkfunctie van de TCO-laag (12) 3,4 eV tot 4,7 eV bedraagt in het geval van de TCO-laag die hoofdzakelijk elektronen transporteert, en/of waarin de werkfunctie van de TCO-laag (12) 4,7 eV tot 6,4 eV bedraagt ingeval de TCO- laag hoofdzakelijk gaten opvangt, en/of waarin de TCO-laag elk afzonderlijk getextureerd is, in het bijzonder met dezelfde textuur als het substraat.The solar cell according to any one of claims 1 to 4, wherein the at least one contact is provided on a TCO layer (12), in particular where the material of the transparent conductive layer (12) is selected from Indium Tin Oxide (ITO), IOH, ZnO, or doped ZnO, such as aluminum doped ZnO, doped Tin Oxide, such as fluorine doped Tin Oxide, doped Indium Oxide, such as Indium Fluorine Oxide (IFO:H), and Indium Tungsten Oxide (IWO), and/or where a thickness of the transparent conductive layer (12) is 10-200 nm, in particular 20-170 nm, more in particular 30-50 nm, and/or where the refractive index of the transparent conductive layer (12) is <2.2, and/or wherein the work function of the TCO layer (12) is from 2 eV to 8 eV, in particular 3.4 eV to 6.4 eV, and/or wherein the work function of the TCO layer (12) is 3.4 eV to 4.7 eV in the case of the TCO layer that mainly transports electrons, and/or where the work function of the TCO layer (12) is 4.7 eV to 6.4 eV in case the TCO layer mainly traps holes, and/or in which the TCO layer is individually textured, in particular with the same texture as the substrate.

6. De zonnecel volgens conclusie 5, waarbij het contact, in het bijzonder een metaalcontact, meer in het bijzonder een contactlaag, de TCO-laag, en optioneel de gedoteerde siliciumlaag een stapel vormen, in het bijzonder een stapel van in wezen gelijkvormige lagen, meer in het bijzonder waarbij een breedte van de gedoteerde siliciumlaag > een breedte van de TCO- laag, welke breedte van de TCO-laag > breedte van de contactlaag.6. The solar cell according to claim 5, wherein the contact, in particular a metal contact, more in particular a contact layer, the TCO layer, and optionally the doped silicon layer form a stack, in particular a stack of essentially identical layers, more specifically, where a width of the doped silicon layer > a width of the TCO layer, which width of the TCO layer > width of the contact layer.

7. De zonnecel volgens een van de conclusies 1-6, waarbij het ten minste één contact is ver- schaft als een strook, meer in het bijzonder als een strook met een breedte van 0,01-200 um, in het bijzonder een breedte van 0,05-50 um.The solar cell according to any one of claims 1 to 6, wherein the at least one contact is provided as a strip, more in particular as a strip with a width of 0.01-200 µm, in particular a width from 0.05-50 um.

8. De zonnecel volgens conclusie 7, waarbij de ten minste één lichtabsorberende laag aan het oppervlak is behandeld, in het bijzonder waarbij de behandeling is gekozen uit behandeling met een gas en behandeling met een plasma, meer in het bijzonder waarbij bij de behande- ling waterstof wordt gebruikt, of waarbij bij de behandeling zuurstof wordt gebruikt, nog meer in het bijzonder waarbij vrijwel uitsluitend waterstof wordt gebruikt, of waarbij vrijwel uitsluitend zuurstof wordt gebruikt.8. The solar cell according to claim 7, wherein the at least one light-absorbing layer has been treated on the surface, in particular wherein the treatment is selected from treatment with a gas and treatment with a plasma, more particularly wherein the treatment hydrogen is used, or where oxygen is used in the treatment, even more particularly where hydrogen is used almost exclusively, or oxygen is used almost exclusively.

9. De zonnecel volgens een van de conclusies 1-8, waarbij het substraat (10) een enkelzijdig of dubbelzijdig vlak substraat (10) oppervlak is, en/of waar het substraat (10) een enkelzijdig of dubbelzijdig getextureerd substraat (10) oppervlak is (ISO 4287:1997), in het bijzonder getextureerd met een oppervlakteruwheid Ra van 1-20 um, zoals 2-10 um, en/of waarbij het getextueerde oppervlak een aspectverhouding (hoogte:diepte van een getextu- eerde structuur) heeft van 2-10.The solar cell according to any one of claims 1 to 8, wherein the substrate (10) is a single-sided or double-sided flat substrate (10) surface, and/or where the substrate (10) is a single-sided or double-sided textured substrate (10) surface (ISO 4287:1997), in particular textured with a surface roughness Ra of 1-20 um, such as 2-10 um, and/or wherein the textured surface has an aspect ratio (height:depth of a textured structure) of 2-10.

10. De zonnecel volgens een van de conclusies 1-9, waarbij het substraat een dikte heeft van 1-500 um, en/of omvattend 10-102! doteringsstoffen/cm’ n- of p-type gedoteerd substraat (10), en/of waar het substraat (10) 1*1012-0,5*10!° n- of p-type doteringsstoffen/cm? omvat, in het bij- zonder 2*10!+-10!7 doteringsstoffen/cm?, meer in het bijzonder 5*101-101 doteringsstof- fen/cm’, zoals 8*101+-3*101 doteringsstoffen/cm’, en/of waarbij het substraat (10) een weerstand heeft van 0,1-1000 ohm*cm bij 300K, meer in het bijzonder 1-100 ohm*cm, zoals 5-10 ohm*cm.The solar cell according to any one of claims 1-9, wherein the substrate has a thickness of 1-500 µm, and/or comprising 10-102 µm. dopants/cm' n- or p-type doped substrate (10), and/or where the substrate (10) 1*1012-0.5*10!° n- or p-type dopants/cm? comprises, in particular 2*10!+-10!7 dopants/cm', more in particular 5*101-101 dopants/cm', such as 8*101+-3*101 dopants/cm' , and/or wherein the substrate (10) has a resistance of 0.1-1000 ohm*cm at 300K, more specifically 1-100 ohm*cm, such as 5-10 ohm*cm.

11. De zonnecel volgens een van de conclusies 1-10, waarbij het ten minste één contact min- der dan 5% van het oppervlak aan de voorkant of achterkant beslaat, in het bijzonder waarbij het ten minste één contact minder dan 1% van het oppervlak aan de voorkant of achterkant beslaat, meer in het bijzonder minder dan 0,5%, en/of waar het contact een metaal omvat, waar het metaal van de contacten onafhankelijk ten min- ste één van Cu, Al, W, Ti, Ni, Cr, Ag omvat, en/of waarbij een dikte van de metaalcontacten (13) 200 nm-50 um bedraagt, in het bijzonder 1-25 Lm, en/of waar het metaalcontact (13) is gekozen uit een metaallaag, een metaalrooster, een metaallijn, of een combinatie daarvan.The solar cell according to any one of claims 1 to 10, wherein the at least one contact covers less than 5% of the surface area on the front or back, in particular where the at least one contact covers less than 1% of the surface area. surface on the front or back, more specifically less than 0.5%, and/or where the contact comprises a metal, where the metal of the contacts independently comprises at least one of Cu, Al, W, Ti, Ni, Cr, Ag, and/or where a thickness of the metal contacts (13) is 200 nm-50 um, in particular 1-25 Lm, and/or where the metal contact (13) is selected from a metal layer, a metal grid, a metal line, or a combination thereof.

12. De zonnecel volgens een van de conclusies 1-11, waarbij ten minste een van het voorop- pervlak en het achteroppervlak is voorzien van een antireflecterende coating (16), in het bij- zonder een antireflecterende coating (16) op het oppervlak dat niet door het contact wordt bedekt.The solar cell according to any one of claims 1 to 11, wherein at least one of the front surface and the rear surface is provided with an anti-reflective coating (16), in particular an anti-reflective coating (16) on the surface that is not covered by the contact.

13. De zonnecel volgens conclusie 12, waarbij de laag onder de antireflecterende coating voorzien is van een oppervlaktebehandeling (17), zoals een oppervlaktebehandeling met Ho, met O», of een combinatie daarvan.The solar cell according to claim 12, wherein the layer under the anti-reflective coating is provided with a surface treatment (17), such as a surface treatment with Ho, with O», or a combination thereof.

14. De zonnecel volgens een van de conclusies 1-13, waarbij de VOC > 700 mV is, in het bijzonder > 725 mV, zoals > 730 mV, en/of waarbij een Jsc > 30 mA/cm? is, in het bijzonder > 38 mA/cm?, zoals > 39 mA/em?, en/of een vulfactor (FF) van > 75%, in het bijzonder > 80%, zoals > 82,5%, en/of met een rendement van > 23%, in het bijzonder > 23,8%, zoals > 23,9%.14. The solar cell according to any one of claims 1-13, wherein the VOC is > 700 mV, in particular > 725 mV, such as > 730 mV, and/or wherein a Jsc > 30 mA/cm? is, in particular > 38 mA/cm?, such as > 39 mA/em?, and/or a fill factor (FF) of > 75%, in particular > 80%, such as > 82.5%, and/or with a return of > 23%, in particular > 23.8%, such as > 23.9%.

15. De silicium hetero-junctie zonnecel (100) volgens een van de conclusies 1-14, waarbij de zonnecel een zonnecel is met tachtercontact, zoals een geïnterdigiteerde zonnecel met achter- contact, of waarin de zonnecel een achter- en voorcontact zonnecel is.The silicon heterojunction solar cell (100) according to any one of claims 1 to 14, wherein the solar cell is a back contact solar cell, such as an interdigitated back contact solar cell, or wherein the solar cell is a back and front contact solar cell.

16. Werkwijze voor het produceren van een silicium hetero-junctie zonnecel (100) met voor- en achtercontact volgens een van de conclusies 1-15, omvattend het verschaffen van een substraat, zoals een kristallijn Si-substraat, het eventueel textureren van het substraat, zoals het dubbelzijdig textureren van het sub- straat, vervolgens het substraat onderdompelen in een sterke oxiderende oplossing, vervolgens het geoxideerde substraat etsen door het geoxideerde substraat onder te dompelen in een zure oplossing direct daarna het geëtste substraat in een laagafzettingsgereedschap plaatsen, en een intrin- sieke Si laag op ten minste één zijde van het geétste substraat afzetten ,A method for producing a silicon heterojunction solar cell (100) with front and back contact according to any one of claims 1 to 15, comprising providing a substrate, such as a crystalline Si substrate, optionally texturing the substrate , such as double-sided texturing of the substrate, then immersing the substrate in a strong oxidizing solution, then etching the oxidized substrate by immersing the oxidized substrate in an acidic solution, then immediately placing the etched substrate into a layer deposition tool, and an internal - deposit a Si layer on at least one side of the etched substrate,

vervolgens het aanbrengen op de intrinsieke Si-laag van ten minste één gedoteerde silicium- laag, in het bijzonder een laag die minder dan 20% van respectievelijk het vooroppervlak of het achteroppervlak beslaat vervolgens een transparante geleidende oxidelaag (TCO) op de ten minste één gedoteerde Si- laag afzetten, in het bijzonder na een eerste uitlijning van de zonnecel, en vervolgens het afzetten van metaalcontacten op de TCO-laag, in het bijzonder na een tweede uitlijning van de zonnecel, meer in het bijzonder waarbij de eerste en tweede uitlijning elk afzonderlijk een nauwkeurig- heid hebben die beter is dan 20 um lateraal, zoals beter dan 1 um lateraal.then applying to the intrinsic Si layer at least one doped silicon layer, in particular a layer covering less than 20% of the front surface or the rear surface respectively, then applying a transparent conductive oxide layer (TCO) to the at least one doped Depositing the Si layer, in particular after a first alignment of the solar cell, and then depositing metal contacts on the TCO layer, in particular after a second alignment of the solar cell, more in particular where the first and second alignment are each individually have an accuracy better than 20 um lateral, such as better than 1 um lateral.

17. Werkwijze volgens conclusie 16, waarbij voor de afzetting van de TCO-laag en/of de metaalcontacten en eventueel voor het aanbrengen van de gedoteerde siliciumlaag een hard masker wordt gebruikt, en/of waarbij contacten en/of contactlagen worden aangebracht door afzetting van metaal en op- heffing van contactloze gebieden, zeefdrukken en elektrisch plateren.17. Method according to claim 16, wherein a hard mask is used for the deposition of the TCO layer and/or the metal contacts and possibly for the application of the doped silicon layer, and/or wherein contacts and/or contact layers are applied by deposition of metal and elimination of non-contact areas, screen printing and electric plating.

18. Silicium hetero-junctie zonnecel (100) volgens een van de conclusies 1-15 en/of verkre- gen door de werkwijze volgens conclusie 16 of 17, omvattend ten minste twee elementen zo- als genoemd in de claims, en/of omvattend ten minste één verder element zoals genoemd in de beschrijving.18. Silicon heterojunction solar cell (100) according to any one of claims 1-15 and/or obtained by the method according to claim 16 or 17, comprising at least two elements as mentioned in the claims, and/or comprising at least one further element as mentioned in the description.