TW201712881A - Metal micro-grid electrode for highly efficient SI microwire solar cells with over 80% fill factor - Google Patents
Metal micro-grid electrode for highly efficient SI microwire solar cells with over 80% fill factor Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
- H01L31/022433—Particular geometry of the grid contacts
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035209—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures
- H01L31/035227—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures the quantum structure being quantum wires, or nanorods
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
- H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
Abstract
Description
該申請要求題為“Metal Micro-grid Electrode for Highly Efficient Si Microwire Solar Cells with over 80% Fill Factor(具有超過80%填充因數的高效Si微線太陽能電池的金屬微網格電極)”並且在2015年5月14日提交的的美國臨時申請號62/161485的優先權，其的公開通過引用全部合併於此。 The application request is entitled "Metal Micro-grid Electrode for Highly Efficient Si Microwire Solar Cells with over 80% Fill Factor" and in 2015, with a metal microgrid electrode of a highly efficient Si microwire solar cell with a fill factor of over 80%" The priority of U.S. Provisional Application No. 62/161,485, filed on May 14, the entire disclosure of which is incorporated herein by reference.
光伏器件(又叫作太陽能電池)是通過光伏效應將太陽光能量直接轉換成電的固態器件。電池的元件用於製作太陽能模組，也稱為太陽能電池板。這些太陽能模組產生的能量(稱為太陽能)是太陽能的示例。 Photovoltaic devices (also known as solar cells) are solid-state devices that convert solar energy directly into electricity through the photovoltaic effect. The components of the battery are used to make solar modules, also known as solar panels. The energy produced by these solar modules (called solar energy) is an example of solar energy.
光伏效應是在暴露于光時在材料中創建電壓(或對應的電流)。儘管光伏效應直接與光電效應有關，這兩個過程是不同的並且應區分開。在光電效應中，在暴露於足夠的能量輻射時從材料的表面噴射電子。光伏效應的不同之處在于生成的電子在材料內的不同帶之間轉移(即，從價帶到導帶)，從而導致在兩個電極之間建立電壓。 The photovoltaic effect is the creation of a voltage (or corresponding current) in a material when exposed to light. Although the photovoltaic effect is directly related to the photoelectric effect, the two processes are different and should be distinguished. In the photoelectric effect, electrons are ejected from the surface of the material upon exposure to sufficient energy radiation. The photovoltaic effect differs in that the generated electrons are transferred between different bands within the material (ie, from the valence band to the conduction band), resulting in the establishment of a voltage between the two electrodes.
光伏是通過使用太陽能電池將來自太陽的能量轉換成電來產生電力的方法。光伏效應指光的光子-太陽能包-使電子撞到較高能量狀 態來產電。在較高能量狀態，電子能夠從它在與半導體中的單原子關聯的正常位置逃逸以變成電路中電流的部分。這些光子包含不同量的能量，其對應於太陽光譜的不同波長。在光子撞擊PV電池時，它們可被反射或吸收，或它們可直接通過。吸收的光子可以產生電。術語光伏指示通過器件的電流完全由光能引起所採用的光電二極體的無偏操作模式。本質上所有光伏器件都是某一類型的光電二極體。 Photovoltaic is a method of generating electricity by converting solar energy from electricity into electricity using a solar cell. Photovoltaic effect refers to the photon-solar package of light - causing electrons to hit higher energy State to produce electricity. In the higher energy state, electrons can escape from its normal position associated with a single atom in the semiconductor to become part of the current in the circuit. These photons contain different amounts of energy, which correspond to different wavelengths of the solar spectrum. When photons hit a PV cell, they can be reflected or absorbed, or they can pass directly. The absorbed photons can generate electricity. The term photovoltaic indicates that the current through the device is completely caused by light energy to the unbiased mode of operation of the photodiode employed. Essentially all photovoltaic devices are a certain type of photodiode.
矽微線(MW)作為用於開發高效和低成本太陽能電池的潛在工具(由於它們的較好光學吸收和有效的載流子分離)已被廣泛研究。垂直對齊的Si MW陣列示出極大增強的光捕獲，其具有最終小於4%的減少表面反射。另外，採用徑向p-n結的基於線的太陽能電池是有益的，因為光吸收和載流子收集通過它們的正交取向而去耦。也就是說，與需要~100μm擴散長度的常規太陽能電池相比，光載流子可以在相對短的徑向方向上(多達線半徑，10μm)分離。然而，Si MW太陽能電池的功率轉換效率(PCE)與常規晶體Si太陽能電池相比仍是相對低的。PCE下降的可能原因之一將是Si MW陣列上的非優化發射極層和頂電極。為了可靠歐姆接觸而沒有由於金屬電極的遮蔽損耗，嘗試讓例如氧化銦錫(ITO)和銀納米線網路等各種透明導電電極(TCE)在Si線和TCE之間形成接觸，但一些報告示出低值的實驗FF引起相對低的電池效率；例如對於ITO和金屬網格集成為匯流條是28%並且對於具有Ni納米粒的Ag納米線網路是55%。FF的嚴重下降主要是由於Si與TCE之間的介面處的高接觸電阻。 Microwires (MW) have been extensively studied as potential tools for the development of efficient and low cost solar cells due to their better optical absorption and efficient carrier separation. The vertically aligned Si MW array shows a greatly enhanced light capture with a reduced surface reflection of less than 4% eventually. Additionally, line-based solar cells employing radial pn junctions are beneficial because light absorption and carrier collection are decoupled by their orthogonal orientation. That is, photocarriers can be in a relatively short radial direction (up to a line radius, compared to conventional solar cells that require a diffusion length of ~100 μm, 10 μm) separation. However, the power conversion efficiency (PCE) of Si MW solar cells is still relatively low compared to conventional crystalline Si solar cells. One of the possible reasons for the drop in PCE will be the non-optimized emitter layer and top electrode on the Si MW array. For reliable ohmic contact without shielding loss due to metal electrodes, attempts have been made to form various transparent conductive electrodes (TCE) such as indium tin oxide (ITO) and silver nanowire networks to form a contact between the Si line and the TCE, but some reports A low value experimental FF results in relatively low cell efficiency; for example, ITO and metal mesh integration is 28% for bus bars and 55% for Ag nanowire networks with Ni nanoparticles. The severe drop in FF is mainly due to the high contact resistance at the interface between Si and TCE.
另一方面，基於單MW太陽能電池上的直接金屬接觸已經證明81%的最高FF值。對於沒有使用TCE的直接金屬接觸，具有低接觸電阻的歐姆接觸需要高導電Si表面。到目前為止，頂電極設計為圍繞MW陣列的方形區域的平面結區域上的金屬膜。從在沒有匯流/指形條的鎢探針(65%)或銦點(57%)中集成的尺寸非常小的電池 (8.5mm2)獲得高FF。因為簡並摻雜的發射極層對於需要較短擴散長度的小型電池中的載流子擴散是相對導電的，可以從Si MW收集載荷子，儘管僅與微尺度區域點接觸也如此。在之前的工作中，穩健的歐姆接觸通過平面區域上選擇性圖案化的Al電極(叫作“邊電池”)來證明，從而從具有1cm2電池尺寸的MW陣列器件產生75.2%的最高FF。儘管在沒有匯流/指形條的情況下獲得最高FF值，由於具有較大結和表面區域的徑向結MW中嚴重的俄歇/表面複合(由具有深結(薄層電阻Rsh：~30Ω/sq)的高導電發射極產生)，MW太陽能電池的PCE與常規電池的仍然沒有可比性。此外，由於MW表面上簡並摻雜區的面密度增加，MW長度的增加也使所有光伏參數(開路電壓(VOC)、JSC、FF)嚴重下降加劇(支援資訊圖S1)。因此，期望不具有該缺點的光伏器件。 On the other hand, direct metal contact on single MW solar cells has demonstrated a maximum FF value of 81%. For direct metal contacts that do not use TCE, ohmic contacts with low contact resistance require highly conductive Si surfaces. Up to now, the top electrode has been designed as a metal film on a planar junction region surrounding a square region of the MW array. Very small size battery integrated from tungsten probes (65%) or indium dots (57%) without confluence/finger strips ( 8.5mm 2 ) Get high FF. Since the degenerately doped emitter layer is relatively conductive for carrier diffusion in small cells requiring shorter diffusion lengths, charge carriers can be collected from the Si MW, although only in point contact with the micro-scale regions. In previous work, robust ohmic contact was demonstrated by selectively patterned Al electrodes (referred to as "edge cells") on the planar area, resulting in a 75.2% highest FF from a MW array device having a cell size of 1 cm2 . Although the highest FF value is obtained without the confluence/finger strip, due to the severe Auger/surface recombination in the radial junction MW with larger junctions and surface areas (from having a deep junction (thin layer resistance R sh :~ The high conductivity emitter of 30 Ω/sq)), the PCE of MW solar cells is still not comparable to conventional batteries. In addition, due to the increased areal density of the degenerate doped regions on the MW surface, the increase in MW length also exacerbates all photovoltaic parameters (open circuit voltage (V OC ), J SC , FF) (support information map S1). Therefore, photovoltaic devices that do not have this disadvantage are desired.
器件包括具有超過80%填充因數的Si微線太陽能電池。器件可以進一步包括具有1至1000微米網格間距的網格圖案上的微網格電極，其中微網格電極經由結附連到Si微線太陽能電池。在一個實施例中，網格間距是10至500微米。 The device includes a Si microwire solar cell with a fill factor of over 80%. The device may further comprise a micromesh electrode on a grid pattern having a grid spacing of 1 to 1000 micrometers, wherein the microgrid electrode is attached to the Si microwire solar cell via a junction. In one embodiment, the grid spacing is from 10 to 500 microns.
在一個實施例中，網格間距是50至400微米。 In one embodiment, the grid spacing is 50 to 400 microns.
在一個實施例中，微網格電極允許結正常運行而沒有光學和電損耗。 In one embodiment, the micromesh electrodes allow the junction to operate normally without optical and electrical losses.
在一個實施例中，結具有10-500Ω/sq的薄層電阻。 In one embodiment, the junction has a sheet resistance of 10-500 Ω/sq.
在一個實施例中，結具有近似100Ω/sq的薄層電阻。 In one embodiment, the junction has a sheet resistance of approximately 100 Ω/sq.
在一個實施例中，Si微線太陽能電池的功率轉換效率通過微網格電極收集光載流子而沒有大量俄歇/表面複合來增強。 In one embodiment, the power conversion efficiency of a Si microwire solar cell is enhanced by collecting photocarriers through the microgrid electrodes without substantial Auger/surface recombination.
在一個實施例中，具有1cm2區域的Si微線太陽能電池示出在565.2mV的開路電壓和35.9mA/cm2多達16.5%的轉換效率。 In one embodiment, a Si microwire solar cell having a 1 cm 2 region shows an open circuit voltage of 565.2 mV and a conversion efficiency of up to 16.5% at 35.9 mA/cm 2 .
在一個實施例中，填充因數是81.2%。 In one embodiment, the fill factor is 81.2%.
在一個實施例中，微網格電極包括約1μm厚度的Ni電極。 In one embodiment, the micromesh electrode comprises a Ni electrode having a thickness of about 1 [mu]m.
圖1：(a)對於具有深(~30Ω/sq的Rsh)和淺(~100Ω/sq的Rsh)結的邊電極電池的實驗(實心符號和線)和類比電流密度-電壓(J-V)曲線圖(開符號)。(b)作為各種器件尺寸範圍內發射極層的薄層電阻的函數的FF值的PC1D模擬結果。 Figure 1: (a) Experiments (solid symbols and lines) and analog current density-voltage (JV) for a side electrode battery with deep (~30 Ω/sq R sh ) and shallow (~100 Ω/sq R sh ) junctions ) Graph (open symbol). (b) PC1D simulation results of FF values as a function of sheet resistance of the emitter layer over various device size ranges.
圖2：(a-d)具有2μm線寬以及50、100、200和400μm的不同網格間距的玻璃襯底上的金屬微網格的光學顯微鏡圖像。(e)在從400至1000nm的主要光譜範圍內求平均的光學傳輸(黑色實心符號)，和作為網格間距的函數的微網格的薄層電阻(藍色實心符號)。紅色的實線代表微網格電極的計算薄層電阻。還示出深結發射極層的薄層電阻(藍色虛線)。插圖示出玻璃襯底上的微網格的光學圖像，其在背景中示出符號標記(UNIST)。 Figure 2: (a-d) Optical microscopy image of a metal microgrid on a glass substrate having a line width of 2 [mu]m and different grid spacings of 50, 100, 200 and 400 [mu]m. (e) The average optical transmission (black solid symbol) in the main spectral range from 400 to 1000 nm, and the sheet resistance (blue solid symbol) of the microgrid as a function of the grid spacing. The solid red line represents the calculated sheet resistance of the microgrid electrode. The sheet resistance (blue dashed line) of the deep junction emitter layer is also shown. The inset shows an optical image of a micro-mesh on a glass substrate showing a symbol mark (UNIST) in the background.
圖3：(a)具有不同間距的金屬微網格的平面結Si太陽能電池的J-V曲線：50(黑色)，100(紅色)，200(綠色)和400(藍色實線和符號)μm。(b)從平面a中標繪的J-V曲線提取的開路電壓(黑色)和短路電流密度(藍色實線和符號)。(c)填充因數(紅色)和效率(綠色實線和符號)標繪為網格間距的函數。由於較寬微網格的較高透射率，效率通過增加微網格的間距而提高。 Figure 3: (a) J-V curves of planar junction Si solar cells with different pitches of metal microgrids: 50 (black), 100 (red), 200 (green) and 400 (blue solid and symbol) μm. (b) Open circuit voltage (black) and short circuit current density (blue solid line and symbol) extracted from the J-V curve plotted in plane a. (c) Fill factor (red) and efficiency (green solid lines and symbols) are plotted as a function of grid spacing. Due to the higher transmittance of the wider micro-mesh, the efficiency is increased by increasing the spacing of the micro-grids.
圖4：具有微網格電極的Si MW太陽能電池的(a)示意圖示、(b)光學以及(c-d)SEM圖像。垂直對齊的Si MW陣列在格線之間形成。 Figure 4: (a) schematic, (b) optical and (c-d) SEM images of a Si MW solar cell with microgrid electrodes. Vertically aligned Si MW arrays are formed between the grid lines.
圖5：(a)由太陽模擬器測量的Ni膜電極的J-V曲線(紅色)和Suns-VOC(藍色實線)。插圖示出通過電鍍法沉積的微網格電極的厚Ni膜。(b)Al膜電極的兩個J-V曲線(紅色：太陽模擬器，藍色實 線：Suns-VOC)和功率輸出曲線(紅色虛線)。通過比較兩個不同的J-V曲線來記錄Jmmp處的△V。(c)作為膜厚度的Ni膜電極的實驗(紅色實心符號)和計算薄層電阻(紅色實線)。Al膜電極在200nm膜厚度的實驗薄層電阻用黑色實心符號標記。(d)作為網格寬度的函數的Ni和Al膜電極的實驗(實心符號)和計算接觸電阻(實線)。插圖示出通過改變接觸墊的節距所測量的電阻的標繪圖；Al(黑色)和Ni(紅色線和符號)膜電極。 Figure 5: (a) JV curve (red) and Suns-V OC (blue solid line) of the Ni film electrode measured by a solar simulator. The inset shows a thick Ni film of a micromesh electrode deposited by electroplating. (b) Two JV curves for the Al film electrode (red: solar simulator, solid blue line: Suns-V OC ) and power output curve (red dotted line). The ΔV at J mmp was recorded by comparing two different JV curves. (c) Experiment (red solid symbol) and calculation of sheet resistance (solid red line) as a film thickness of the Ni film electrode. The experimental sheet resistance of the Al film electrode at a film thickness of 200 nm was marked with a black solid symbol. (d) Experiments (solid symbols) of Ni and Al film electrodes as a function of grid width and calculation of contact resistance (solid line). The inset shows a plot of the resistance measured by changing the pitch of the contact pads; Al (black) and Ni (red lines and symbols) membrane electrodes.
圖S1：具有邊電極的Si微線太陽能電池的(a)光學和(b)SEM圖像。(c)具有各種長度的Si微線的平面和微線太陽能電池的J-V曲線。(d)具有~30Ω/sq薄層電阻的深發射極的二次離子質譜分佈。由於微線表面上簡並摻雜區的面密度增加，微線長度增加使功率轉換效率的嚴重下降加劇。 Figure S1: (a) optical and (b) SEM images of Si microwire solar cells with edge electrodes. (c) J-V curves of planar and microwire solar cells with various lengths of Si microwires. (d) Secondary ion mass spectrometry distribution of deep emitters with a sheet resistance of ~30 Ω/sq. As the areal density of the degenerate doped regions on the surface of the microwire increases, the increase in the length of the microwires exacerbates the severe drop in power conversion efficiency.
圖S2：具有~100Ω/sq薄層電阻的淺發射極的二次離子質譜分佈，其中結深估計為~220nm並且表面濃度測量為6.2×1019cm-3。 Figure S2: Secondary ion mass spectrometry distribution of a shallow emitter with a sheet resistance of ~100 Ω/sq, where the junction depth is estimated to be ~220 nm and the surface concentration is measured to be 6.2 x 10 19 cm -3 .
圖S3：玻璃襯底上的微網格的透射光譜。對較大間距觀察到透射率整體增加，這歸因於在間距增加時被Al膜覆蓋的表面面積減小。 Figure S3: Transmission spectrum of a microgrid on a glass substrate. An overall increase in transmittance was observed for a larger pitch due to a reduction in the surface area covered by the Al film as the pitch was increased.
圖S4：具有邊(黑色)和微網格電極(紅色符號和線)的Si微線太陽能電池的J-V曲線。功率轉換效率從9.6%增加到15.4%連同VOC和FF值提高。 Figure S4: JV curve of a Si microwire solar cell with sides (black) and microgrid electrodes (red symbols and lines). The power conversion efficiency increased from 9.6% to 15.4% along with an increase in V OC and FF values.
本文描述可操作成將光轉換成電的光伏器件，其包括襯底、基本上垂直於該襯底的多個結構以及這些結構之間的一個或多個凹陷。如本文使用的術語“光伏器件”意指可以通過將光(例如太陽輻射)轉換成電來產生電力的器件。如本文使用的術語單晶意指整個結構的晶格在整個結構中是連續且完整的，其中基本上沒有晶界。導電材料可以是具有基本上零帶隙的材料。導電材料的電導率大體上在103S/cm 以上。半導體可以是具有多達約3eV的有限帶隙的材料並且一般具有在103至10-8S/cm範圍內的電導率。電絕緣材料可以是具有大於約3eV的帶隙的材料並且大體上具有在10-8S/cm以下的電導率。如本文使用的術語“基本上垂直於襯底的結構”意指結構與襯底之間的角度在85°至90°。如本文使用的術語“凹陷”意指襯底中的中空空間並且對襯底外部的空間開放。 Described herein are photovoltaic devices operable to convert light into electricity, including a substrate, a plurality of structures substantially perpendicular to the substrate, and one or more recesses between the structures. The term "photovoltaic device" as used herein means a device that can generate electricity by converting light, such as solar radiation, into electricity. The term single crystal as used herein means that the crystal lattice of the entire structure is continuous and intact throughout the structure, with substantially no grain boundaries. The electrically conductive material can be a material having a substantially zero band gap. The conductivity of the electrically conductive material is substantially above 10 3 S/cm. The semiconductor can be a material having a finite band gap of up to about 3 eV and typically has a conductivity in the range of 10 3 to 10 -8 S/cm. The electrically insulating material can be a material having a band gap greater than about 3 eV and generally has a conductivity below 10 -8 S/cm. The term "substantially perpendicular to the structure of the substrate" as used herein means that the angle between the structure and the substrate is between 85 and 90. The term "recessed" as used herein means a hollow space in a substrate and is open to a space outside the substrate.
單晶半導體材料可以從由矽、鍺、III-V族化合物材料、II-VI族化合物材料和四級材料組成的組選擇。如本文使用的III-V族化合物材料意指由III族元素和V族元素組成的化合物。III族元素可以是B、Al、Ga、In、Tl、Sc、Y、鑭系元素和錒系元素。V族元素可以是V、Nb、Ta、Db、N、P、As、Sb和Bi。如本文使用的II-VI族化合物材料意指由II族元素和VI族元素組成的化合物。II族元素可以是Be、Mg、Ca、Sr、Ba和Ra。VI族元素可以是Cr、Mo、W、Sg、O、S、Se、Te和Po。四級材料是由四個元素組成的化合物。 The single crystal semiconductor material may be selected from the group consisting of ruthenium, osmium, a III-V compound material, a II-VI compound material, and a quaternary material. The III-V compound material as used herein means a compound composed of a group III element and a group V element. Group III elements can be B, Al, Ga, In, Tl, Sc, Y, lanthanides and actinides. The group V elements may be V, Nb, Ta, Db, N, P, As, Sb, and Bi. A II-VI compound material as used herein means a compound composed of a Group II element and a Group VI element. Group II elements can be Be, Mg, Ca, Sr, Ba, and Ra. Group VI elements can be Cr, Mo, W, Sg, O, S, Se, Te, and Po. The quaternary material is a compound composed of four elements.
結構可以是具有從由橢圓形、圓形、矩形和多邊形橫截面、條或網格組成的組選擇的橫截面的圓柱或棱柱。如本文使用的術語“網格”意指網狀模式或構造。結構可以是具有50nm至5000nm直徑、1000nm至20000nm高度、兩個最近柱體之間300nm至15000nm的中心距的柱體。如本文使用的術語“電極”意指用於建立與光伏器件的電接觸的導體。 The structure may be a cylinder or prism having a cross section selected from the group consisting of elliptical, circular, rectangular and polygonal cross sections, strips or meshes. The term "grid" as used herein means a mesh pattern or configuration. The structure may be a cylinder having a diameter of 50 nm to 5000 nm, a height of 1000 nm to 20000 nm, and a center distance of 300 nm to 15000 nm between the two closest cylinders. The term "electrode" as used herein refers to a conductor used to establish electrical contact with a photovoltaic device.
襯底可以具有與結構相對的平坦表面。該平坦表面具有摻雜層和可選地設置在摻雜層上並且與之形成歐姆接觸的金屬層。歐姆接觸是這樣的區，跨其的電流-電壓(I-V)曲線是線性且對稱的。襯底可以具有至少50微米的厚度。 The substrate can have a flat surface opposite the structure. The planar surface has a doped layer and a metal layer optionally disposed on the doped layer and forming an ohmic contact therewith. An ohmic contact is a region across which the current-voltage (I-V) curve is linear and symmetrical. The substrate can have a thickness of at least 50 microns.
結構可以具有設置在陣列中的柱體；每個結構的高度是約5微米；結構的節距是300nm到15微米。 The structure may have pillars disposed in the array; the height of each structure is about 5 microns; the pitch of the structure is 300 nm to 15 microns.
根據本文的實施例，用於提高MW太陽能電池的性能的策略應包括i)使MW發射極的摻雜劑濃度和結深減少以便抑制俄歇複合，這導致較高VOC和JSC，(ii)使電極之間的距離變窄以從非導電發射極(即，淺結)收集載荷子而沒有電損耗，這使FF增加，以及(iii)使電池表面上金屬電極的面積最小化以減少遮蔽損耗，這直接增強JSC。 According to embodiments herein, strategies for improving the performance of MW solar cells should include i) reducing the dopant concentration and junction depth of the MW emitter to suppress Auger recombination, which results in higher V OC and J SC , ( Ii) narrowing the distance between the electrodes to collect charge carriers from the non-conductive emitter (ie, shallow junction) without electrical loss, which increases FF, and (iii) minimizes the area of the metal electrode on the surface of the battery Reduces shadowing losses, which directly enhances J SC .
根據本文的實施例，申請者將新穎的金屬微網格併入MW太陽能電池作為頂電極。由於微網格電極較好的光學透射率和電導率，將實現穩健且可靠的歐姆接觸以用於通過頂電極有效收集載荷子同時使與由於金屬電極的遮蔽關聯的光吸收的損耗減小。另外，微網格電極的電導率通過電鍍具有約1μm厚度的厚Ni膜而明顯提高，這導致MW太陽能電池中超過81%的FF。FF的顯著提高可以源於金屬網格與發射極層之間的接觸電阻減小以及微網格電極的低電阻。申請者的具有金屬微網格電極的MW太陽能電池展現16.5%的轉換效率，其與邊電極的相比是提高72%的值。該新穎電極結構因此被視為未來朝著高效微線太陽能電池的實際實現的重要步驟。 In accordance with embodiments herein, Applicants incorporate a novel metal microgrid into a MW solar cell as the top electrode. Due to the better optical transmittance and conductivity of the microgrid electrodes, a robust and reliable ohmic contact will be achieved for efficient collection of charge carriers through the top electrode while reducing losses associated with light absorption associated with shadowing of the metal electrodes. In addition, the electrical conductivity of the microgrid electrode was significantly improved by electroplating a thick Ni film having a thickness of about 1 μm, which resulted in more than 81% of FF in the MW solar cell. A significant increase in FF can result from reduced contact resistance between the metal grid and the emitter layer and low resistance of the microgrid electrode. The applicant's MW solar cell with metal microgrid electrodes exhibits a conversion efficiency of 16.5%, which is a 72% increase compared to the edge electrode. This novel electrode structure is therefore considered an important step towards the practical implementation of high efficiency microwire solar cells in the future.
圖1a示出對於具有深(~30Ω/sq的Rsh)和淺(~100Ω/sq的Rsh)結的邊電極電池的實驗和類比電流密度-電壓(J-V)曲線。類比結果通過使用一維太陽能電池建模程式(PC1D)而獲得並且與實驗資料很好匹配。在淺結(圖2a中紅色和綠色圓)的情況下，J-V曲線示出與深結相比電流密度值的相對突增和較低VOC。由於發射極的不足電導率，在淺結中產生的載流子通過具有高串聯電阻的邊電極被無效收集。另一方面，由於俄歇複合減少(因為高摻雜區的深度(1020cm-3)減小)，JSC的值從20.2明顯增加到25mA/cm2(支援資訊圖S2)。此外，FF值隨著發射極層的薄層電阻增加而明顯減小，但0.01cm2的極小電池尺寸的情況除外，如在圖1b中示出的。由於FF嚴重下降，模擬 結果指示邊電極的設計對於大尺度電池中的電荷收集將並不是有效的。因此，頂部金屬電極應重新設計成有效收集載荷子同時使光學和電損耗最小化。 Figure 1a shows for having a deep (~ 30Ω / sq to R sh) and light (~ 100Ω / sq to R sh) and analog test current density of the junction electrode of the cell edge - voltage (JV) curve. The analogy results were obtained using a one-dimensional solar cell modeling program (PC1D) and matched well with the experimental data. In the case of shallow junctions (red and green circles in Figure 2a), the JV curve shows a relative burst of current density values and a lower V OC compared to the deep junction. Due to the insufficient conductivity of the emitter, carriers generated in the shallow junction are inefficiently collected by the edge electrode having a high series resistance. On the other hand, due to the reduction of Auger recombination (because of the depth of highly doped regions ( 10 20 cm -3 ) decreases), the value of J SC is significantly increased from 20.2 to 25 mA/cm 2 (support map S2). Furthermore, the FF value is significantly reduced as the sheet resistance of the emitter layer is increased, except for the case of a very small cell size of 0.01 cm 2 , as shown in Figure 1b. Due to the severe drop in FF, the simulation results indicate that the design of the edge electrode will not be effective for charge collection in large scale cells. Therefore, the top metal electrode should be redesigned to efficiently collect charge carriers while minimizing optical and electrical losses.
圖2a-d示出具有2μm線寬以及50、100、200和400μm的不同網格間距的玻璃襯底上的新穎金屬微網格的光學顯微鏡圖像，在相同放大率下拍攝這些圖像。微網格使用光刻工藝、後跟200nm厚Al膜的熱蒸發而成功製造，從而導致形成連續且均勻的方形圖案。微網格電極的光學和電性質如在圖2e中示出的那樣測量。平均透射率值隨著間距增加而增加，這歸因於在間距增加時被Al膜覆蓋的表面面積減小(支援資訊圖S3)。由於具有400μm間距的電極的高透明度(97.9%的透射率)，圖2e的插圖中的照片清楚示出背景中的符號標記(UNIST)。對於微網格電極的電特性，具有各種間距的實驗Rsh值(藍色實心符號)用計算的Rsh(圖2e中的紅色實線)標繪。微網格電極的Rsh通過以下計算：
其中因為由N×N行組成的具有方形圖案的微網格電極遵循基爾霍夫定則16，N、ρ、L、w、和t分別代表1cm寬度中線的數量、Al的電阻率、網格間距、寬度和Al膜的厚度。在1cm×1cm的電池區域(N24)中，因為N(1+N)接近一，計算的Rsh簡單地由ρL/wt給出。對於50、100、200和400μm，實驗Rsh分別是3.1±1.7、7.2±2.0、14.5±1.9和24.9±2.8Ω/sq。這些值與計算Rsh很好匹配，這示出與模型吻合良好。微網格電極的Rsh用閘道間距來線性標度。如果網格間距增加到超過450μm，可以預期Rsh將高於30Ω/sq，這是深結發射極的Rsh(在圖2e中左側y軸處的水準虛線)。即，具有比450μm還大的網格間距的太陽能電池將示出劇烈的FF下降，如用圖1b中的模擬結果解釋的。 Wherein the micromesh electrode having a square pattern consisting of N×N rows follows the Kirchhoff's rule 16 , N, ρ, L, w, and t represent the number of lines in the 1 cm width, the resistivity of Al, and the net The grid spacing, the width, and the thickness of the Al film. In the battery area of 1cm × 1cm (N In 24), since N(1+N) is close to one, the calculated R sh is simply given by ρL/wt. For 50, 100, 200, and 400 μm, the experimental R sh were 3.1 ± 1.7, 7.2 ± 2.0, 14.5 ± 1.9, and 24.9 ± 2.8 Ω/sq, respectively. These values match well with the calculated R sh , which shows good agreement with the model. The R sh of the micro grid electrode is linearly scaled by the gate pitch. If the grid spacing is increased beyond 450 μm, it can be expected that R sh will be higher than 30 Ω/sq, which is the R sh of the deep junction emitter (the horizontal dashed line at the left y-axis in Figure 2e). That is, a solar cell having a grid spacing greater than 450 μm will show a dramatic FF drop, as explained by the simulation results in Figure 1b.
為了評估製造的微網格作為Si太陽能電池中的頂電極的潛在使用，申請者分析在AM 1.5G照度下具有金屬微網格電極的平面結Si太陽能電池的J-V曲線(圖3a)。由於透射率改變，JSC值隨著微網格間距的增加而明顯增加，如在圖3b中示出的。與JSC的趨勢相似，VOC值也趨於隨網格間距增加而增加。VOC提高主要是由於如下列關係中JSC的增加：
其中q、kB、T、JL和J0分別代表電子電荷、玻爾茲曼常數、溫度、光生電流和反向飽和電流。另一方面，FF並未受到微網格電極間距的極大影響，如在圖3c中示出的。根據類比資料，如果發射極的Rsh在1cm2電池尺寸中小於30Ω/sq，光載流子通過頂電極被有效收集而沒有電損耗。表1示出具有邊和微網格電極的太陽能電池的光伏性質。由於VOC和JSC增強，轉換效率通過使用具有400μm網格間距的金屬微網格電極而從6.7%(邊電極)提高到11.3%。 Where q, k B , T, J L and J 0 represent electron charge, Boltzmann constant, temperature, photogenerated current and reverse saturation current, respectively. On the other hand, the FF is not greatly affected by the microgrid electrode spacing, as shown in Figure 3c. According to analogy, if the emitter R sh is less than 30 Ω/sq in a 1 cm 2 cell size, photocarriers are efficiently collected through the top electrode without electrical loss. Table 1 shows the photovoltaic properties of solar cells with edge and micromesh electrodes. Due to the enhancement of V OC and J SC , the conversion efficiency was increased from 6.7% (edge electrode) to 11.3% by using a metal microgrid electrode having a grid pitch of 400 μm.
具有400μm網格間距的微網格電極(示出平面太陽能電池中的最高PCE)被應用於Si微線太陽能電池。詳細器件特徵在圖4a中圖示。由於多達網格間距(~200μm)一半的較短擴散長度，垂直對齊的Si MW陣列在格線之間設計，使得線陣列中的光生載流子可以通過金屬微網格的頂電極而有效收集。Si MW和微網格使用光刻後跟反應離子蝕刻(RIE)來製造，從而導致在微網格的方形圖案中形成MW陣列，如在圖4b和4c的SEM圖像中示出的。 A micromesh electrode having a grid pitch of 400 μm (showing the highest PCE in a planar solar cell) was applied to a Si microwire solar cell. Detailed device features are illustrated in Figure 4a. Due to the short diffusion length of half the grid spacing (~200μm), the vertically aligned Si MW arrays are designed between the grid lines so that the photogenerated carriers in the line array can be effectively passed through the top electrode of the metal microgrid. collect. The Si MW and micro-mesh were fabricated using photolithography followed by reactive ion etching (RIE), resulting in the formation of a MW array in a square pattern of micro-grids, as shown in the SEM images of Figures 4b and 4c.
然後使用旋塗摻雜(SOD)技術進行磷摻雜以形成具有~100Ω/sq的Rsh的淺p-n結，其中基於二次離子質譜(SIMS)分佈，結深估計為~220nm並且表面濃度測量為6.2×1019cm-3(支援資訊圖S2)。薄SiNx層(60nm厚)通過等離子體增強化學氣相沉積(PECVD)而沉積為鈍
化層以及抗反射層。具有微網格電極和邊電極的兩個MW太陽能電池的發射極具有~100Ω/sq的Rsh的淺結。在將微網格電極應用于MW電池時，PCE從9.6%增加到15.4%連同VOC和FF值提高(支援資訊圖S4)。特別地，微網格電極的FF(75.1%)與邊電極(52.1%)相比顯著提高，這需要通過淺發射極的相對非導電通道的較長載流子擴散長度(多達電池尺寸的一半，~5mm)。這主要是由於太陽能電池的串列電阻(Rs)減小，該串聯電阻是金屬電極(Rm)、接觸(Rc)、發射極和基底的電阻總和。申請者可以忽略發射極和基底電阻的影響，因為假設它們不隨前電極的結構而改變。在電阻參數之中，Rc可以使用18來計算
其中Rsh是薄層電阻，L是網格長度，ρc是接觸電阻率，W是網格寬度，Lc是單位電池長度，s是網格間距。該計算能夠對邊和微網格電極的不同s值估計Rs。因為邊電極被視為毫米尺度的網格結構，邊電極的間距(1cm)比微網格電極的(400μm)要長得多。根據方程3，微網格電極的Rc與邊電極相比可以顯著減少25倍。因此，FF提高可以通過Rs和Rc的總和隨著應用微網格電極而減小這一事實來解釋。另外，因為通過以較短擴散長度將載流子傳輸到頂電極來抑制複合，從而導致反向飽和電流減小，VOC可以從501mV提高到564mV(方程2)。儘管JSC由於從僅具有前表面的1%覆蓋的金屬網格的光反射而在微網格電極中從37.0略微減小到36.3mA/cm2，MW太陽能電池的電池效率通過用高導電微網格電極有效收集載流子而顯著提高。為了實現超過80%的高FF，申請者試圖設想進一步改進的頂電極，其具有減少的Rm和Rc同時使遮蔽損耗最小化。 Where R sh is the sheet resistance, L is the grid length, ρ c is the contact resistivity, W is the grid width, L c is the unit cell length, and s is the grid spacing. This calculation can estimate R s for different s values of the edges and microgrid electrodes. Since the side electrodes are considered to be a millimeter-scale grid structure, the pitch of the side electrodes (1 cm) is much longer than that of the micro grid electrodes (400 μm). According to Equation 3, the R c of the microgrid electrode can be significantly reduced by a factor of 25 compared to the edge electrode. Therefore, the FF increase can be explained by the fact that the sum of R s and R c decreases as the microgrid electrode is applied. In addition, since the recombination is suppressed by transporting carriers to the top electrode with a shorter diffusion length, resulting in a decrease in reverse saturation current, V OC can be increased from 501 mV to 564 mV (Equation 2). Although J SC is slightly reduced from 37.0 to 36.3 mA/cm 2 in the microgrid electrode due to light reflection from a 1% covered metal mesh with only the front surface, the cell efficiency of the MW solar cell is achieved by using high conductivity micro The grid electrode effectively collects carriers and is significantly improved. In order to achieve a high FF of over 80%, Applicants attempted to envisage a further improved top electrode with reduced Rm and Rc while minimizing shadowing losses.
為了使Rs最小化而沒有光學損耗，申請者應用電鍍法來沉積厚Ni 膜。與例如物理氣相沉積(PVD)等真空工藝相比，電鍍法為了成本有效的太陽能電池能夠在溶液中用高沉積速率沉積金屬膜。使用電鍍法沉積的1μm厚的Ni膜在圖5a的插圖中示出。高緻密的厚Ni層用微網格模式均勻塗覆，從而對於MW太陽能電池導致FF從75.1%明顯提高到81.2%。因此，MW太陽能電池的最佳性能實現16.5%的PCE連同分別是565mV和35.9mA/cm2的VOC和JSC。為了定量估計微網格電極對提高的FF的影響，具有厚Ni膜(1μm厚，電鍍法)和Al電極(200nm厚，熱蒸發)的MW太陽能電池的Rs值通過將使用太陽模擬器獲得的J-V曲線(紅線)與使用Suns-VOC測量的那些(藍線)比較來提取，如在圖5a和5b中示出的。因為Suns-VOC測量在缺乏Rs的情況下提供理想J-V曲線，通過使兩個不同J-V曲線中的電壓之間的差(△V)除以圖5b中給出的最大功率點(Jmmp)處的電流密度來計算Rs。1μm厚Ni膜的真實J-V曲線(包括Rs，太陽模擬器)幾乎與如在圖5a中示出的理想J-V曲線(排除Rs，Suns-VOC)重疊，而200nm厚的Al膜電極在兩個J-V曲線之間具有明顯的電壓差距(圖5b)。基於計算，Ni膜電極的提取Rs(0.645Ω cm2)比沉積的Al膜電極的(1.51Ω cm2)低得多。如上文提到的，申請者可以由於小的電池結構而僅考慮Rm和Rc值(頂電極除外)。Ni膜的Rsh隨Ni厚度(容易通過沉積時間來控制)增加而減小，如在圖5c中示出的。由於厚度增加，與200nm厚Al膜電極的24.9Ω/sq(圖5c中的黑色符號)相比，Ni膜電極的Rsh減小多達3.7Ω/sq。 In order to minimize R s without optical loss, the applicant applied an electroplating method to deposit a thick Ni film. Compared to vacuum processes such as physical vapor deposition (PVD), electroplating is capable of depositing metal films in solution at high deposition rates for cost effective solar cells. A 1 μm thick Ni film deposited using electroplating is shown in the inset of Figure 5a. The highly dense thick Ni layer is uniformly coated in a micro-mesh mode, resulting in a significant increase in FF from 75.1% to 81.2% for MW solar cells. Therefore, the optimum performance of the MW solar cell achieves 16.5% PCE along with V OC and J SC of 565 mV and 35.9 mA/cm 2 , respectively. In order to quantitatively estimate the effect of the microgrid electrode on the improved FF, the R s value of a MW solar cell with a thick Ni film (1 μm thick, electroplating) and an Al electrode (200 nm thick, thermal evaporation) is obtained by using a solar simulator. The JV curve (red line) is extracted compared to those measured using Suns-V OC (blue line), as shown in Figures 5a and 5b. Because the Suns-V OC measurement provides an ideal JV curve in the absence of R s by dividing the difference between the voltages in two different JV curves (ΔV) by the maximum power point given in Figure 5b (J mmp The current density at ) is calculated as R s . The true JV curve of a 1 μm thick Ni film (including R s , solar simulator) almost overlaps with the ideal JV curve (excluding R s , Suns-V OC ) as shown in Figure 5a, while the 200 nm thick Al film electrode is There is a significant voltage difference between the two JV curves (Figure 5b). Based on the calculation, the extraction of Ni film electrode R s (0.645 Ω cm 2 ) is much lower than that of the deposited Al film electrode (1.51 Ω cm 2 ). As mentioned above, the applicant can consider only the Rm and Rc values (except for the top electrode) due to the small cell structure. The R sh of the Ni film decreases as the thickness of Ni (which is easily controlled by deposition time) increases, as shown in Figure 5c. Due to the increase in thickness, the R sh of the Ni film electrode was reduced by as much as 3.7 Ω/sq as compared with 24.9 Ω/sq of the 200 nm thick Al film electrode (black symbol in Fig. 5c).
另外，Ni膜電極的Rc值(紅色符號)與Al膜電極的(黑色符號)相比明顯減小，如在圖5d中示出的。Rc和接觸電阻率(ρc)通過傳輸線模型(TLM)來測量。在各種金屬和Si之間的介面處的ρc的值通過測量金屬/Si的電阻(排除金屬和Si兩者的本征電阻)來提取。這些電阻通過調整兩個金屬墊之間的節距數量而測量。在網格節距的零點 (在圖5d的插圖中與y軸的交點)處，在不影響發射極的情況下通過兩個網格接觸來誘導電阻。Ni/Si接觸的提取ρc在1.35×10-3cm2的接觸面積是1.69mΩ cm2，而Al/Si接觸實現2.63mΩ cm2的ρc。ρc的提高可以通過新的電流路徑來解釋，這些電流路徑通過在電鍍期間用Ni層填充SiNx層的針孔而形成。基於提取的ρc，Ni(紅線)和Al電極(黑線)的Rc值作為網格寬度的函數(圖5d)從方程3計算。為了獲得比Ni膜電極的還低的Rc，Al膜電極的網格寬度需要寬過10μm，從而導致遮蔽損耗並且然後JSC下降。也就是說，與網格寬度成比例的遮蔽損耗可以通過使用具有相同或甚至更低Rc的較窄寬度的Ni膜電極而減少，這是因為Ni膜電極的Rc減小主要是由於Ni和Si之間的介面處ρc的減少。因此，81.2%的最高FF可以通過不僅使金屬電阻減少而且還使接觸電阻減少來實現。 In addition, the R c value (red sign) of the Ni film electrode is significantly reduced as compared with the (black symbol) of the Al film electrode, as shown in FIG. 5d. R c and contact resistivity (ρ c ) are measured by a transmission line model (TLM). The value of ρ c at the interface between various metals and Si is extracted by measuring the resistance of the metal/Si (excluding the intrinsic resistance of both metal and Si). These resistances are measured by adjusting the number of pitches between the two metal pads. At the zero point of the grid pitch (the intersection with the y-axis in the inset of Figure 5d), the resistance is induced by two grid contacts without affecting the emitter. The contact area of the Ni/Si contact extraction ρ c at 1.35 × 10 -3 cm 2 is 1.69 mΩ cm 2 , and the Al/Si contact achieves ρ c of 2.63 mΩ cm 2 . The increase in ρ c can be explained by a new current path formed by filling the pinholes of the SiN x layer with a Ni layer during electroplating. The R c value based on the extracted ρ c , Ni (red line) and Al electrode (black line) is calculated from Equation 3 as a function of the grid width ( FIG. 5 d ). In order to obtain a lower R c than the Ni film electrode, the mesh width of the Al film electrode needs to be wider than 10 μm, resulting in a shadow loss and then a decrease in J SC . That is, the masking loss proportional to the width of the grid can be reduced by using a Ni film electrode having a narrower width of the same or even lower R c because the decrease in R c of the Ni film electrode is mainly due to Ni. Reduction of ρ c at the interface between and Si. Therefore, the highest FF of 81.2% can be achieved by not only reducing the metal resistance but also reducing the contact resistance.
申請者通過使用金屬微網格電極作為頂部接觸而開發出具有81.2%的FF值的高效(16.5%)MW太陽能電池。由於微網格電極的較好透射率和電導率，FF和VOC值通過淺發射極太陽能電池中頂電極來有效收集光載流子而提高。另外，厚的Ni膜使用電鍍法沉積到微網格電極上；因此，微網格電極的Rm和Rc與通過熱沉積形成的Al膜電極相比極大減小。我們的微網格電極因此明確代表非常有前景的高效MW太陽能電池結構。 Applicants developed a high efficiency (16.5%) MW solar cell with an FF value of 81.2% by using a metal microgrid electrode as the top contact. Due to the better transmittance and conductivity of the microgrid electrodes, the FF and V OC values are increased by the efficient collection of photocarriers by the top electrode in the shallow emitter solar cell. In addition, a thick Ni film is deposited onto the microgrid electrode using electroplating; therefore, the R m and R c of the micromesh electrode are greatly reduced as compared with the Al film electrode formed by thermal deposition. Our microgrid electrodes therefore clearly represent a very promising high efficiency MW solar cell structure.
支援資訊：實驗部分；具有深發射極和邊電極的Si微線太陽能電池的光伏特性；深和淺發射極的二次離子質譜分佈；微網格的透射光譜；具有邊和微網格電極的Si微線太陽能電池的光伏特性。 Supporting information: Experimental section; Photovoltaic characteristics of Si microwire solar cells with deep emitter and edge electrodes; Secondary ion mass spectrometry distribution of deep and shallow emitters; Transmission spectra of microgrids; Edge and microgrid electrodes Photovoltaic properties of Si microwire solar cells.
實驗experiment
垂直Si微線陣列的製造 Fabrication of vertical Si microwire arrays
具有微格線的Si微線(MW)陣列由浮區(Fz)p型Si晶圓(1-5Ω.cm的電阻率，550μm厚)製造。圓形光致抗蝕劑點陣列(直徑2μm，1μm間距)使用AZ nLOF 2035光致抗蝕劑(AZ電子材料)通過光刻而週期性圖案化。然後，垂直對齊的Si MW通過利用1500W光源、100W存儲功能、45毫托氣壓在SF6/C4F8=250/150的源氣體比率下反應離子蝕刻(RIE，Tegal 200)而製造。在RIE工藝後，所得的聚合塗層和對線側壁的蝕刻損害使用piranha溶液(H2SO4：H2O2=2：1)後跟持續10秒的慢Si蝕刻(RSE-100，Transene)而去除。 A Si microwire (MW) array having micro-grids is fabricated from a floating-region (Fz) p-type Si wafer (having a resistivity of 1-5 Ω·cm, 550 μm thick). A circular array of photoresist dots (2 μm in diameter, 1 μm pitch) was periodically patterned by photolithography using AZ nLOF 2035 photoresist (AZ electronic material). Then, the vertically aligned Si MW was fabricated by reactive ion etching (RIE, Tegal 200) at a source gas ratio of SF 6 /C 4 F 8 =250/150 using a 1500 W light source, a 100 W storage function, and a 45 mTorr gas pressure. After the RIE process, the resulting polymeric coating and etch damage to the sidewalls of the wire were treated with a piranha solution (H 2 SO 4 :H 2 O 2 =2:1) followed by a slow Si etch for 10 seconds (RSE-100, Transene) ) and removed.
具有微網格電極的Si微線太陽能電池的製造 Fabrication of Si microwire solar cells with microgrid electrodes
發射極層通過磷擴散經由旋塗摻雜劑(SOD)法而形成。首先，用乙醇(P509：乙醇=1：3)稀釋的磷摻雜劑源(P509，Filmtronics,Inc.)在模擬Si晶圓上旋塗，並且然後在200℃烘烤10分鐘。為了在MW上形成共形摻雜，我們放置Si MW樣品使得它面對磷塗覆的模擬晶圓。在850℃在20% O2和80% N2的混合環境下在管式爐中實施擴散摻雜。SOD擴散中留下的磷玻璃通過使用稀釋HF溶液而去除。在去除磷玻璃和SiOx層後，通過PE-CVD(PEH-600，SORONA)沉積薄SiNx層(60nm厚)。在創建微網格電極中，在使用光刻工藝金屬沉積 之前，用光致抗蝕劑(AZ4330、AZ電子材料，~10μm厚度)覆蓋Si MW。對於頂部和底部接觸，200nm厚的Al膜使用熱蒸發器在樣品頂部和底部上沉積。最後，通過使樣品浸入丙酮溶液來去除光致抗蝕劑。 The emitter layer is formed by a phosphorus diffusion method via a spin-on dopant (SOD) method. First, a phosphorus dopant source (P509, Filmtronics, Inc.) diluted with ethanol (P509: ethanol = 1:3) was spin-coated on a simulated Si wafer, and then baked at 200 ° C for 10 minutes. To form a conformal doping on the MW, we placed the Si MW sample such that it faced the phosphor coated simulated wafer. Diffusion doping was carried out in a tube furnace at 850 ° C in a mixed environment of 20% O 2 and 80% N 2 . The phosphorus glass left in the SOD diffusion is removed by using a diluted HF solution. After removing the phosphor glass and SiO x layers, a thin SiN x layer (60 nm thick) was deposited by PE-CVD (PEH-600, SORONA). In the creation of the microgrid electrode, the Si MW was covered with a photoresist (AZ4330, AZ electronic material, ~10 μm thickness) before metal deposition using a photolithography process. For the top and bottom contacts, a 200 nm thick Al film was deposited on the top and bottom of the sample using a thermal evaporator. Finally, the photoresist is removed by immersing the sample in an acetone solution.
具有厚Ni膜的微網格電極的製造 Fabrication of microgrid electrodes with thick Ni film
為了進一步提高微網格電極的電特性，嘗試電鍍法來沉積厚Ni膜。Ti/Ni作為電鍍的種子層被首先沉積到光致抗蝕劑的微網格圖案上。在沉積種子層後，光致抗蝕劑的餘下部分通過浸入丙酮溶液而去除。然後在由NiSO4．6H2O(1M)、NiCl2．6H2O(0.5M)和H3BO3(1M)組成的Ni溶液中在40℃在5mA/cm2的恒定電流密度下進行電鍍沉積。 In order to further improve the electrical characteristics of the microgrid electrode, an electroplating method was attempted to deposit a thick Ni film. Ti/Ni is first deposited as a seed layer for electroplating onto the micro-mesh pattern of the photoresist. After depositing the seed layer, the remainder of the photoresist is removed by immersion in an acetone solution. Then in by NiSO 4 . 6H 2 O (1M), NiCl 2 . Electroplating was carried out in a Ni solution consisting of 6H 2 O (0.5 M) and H 3 BO 3 (1 M) at 40 ° C at a constant current density of 5 mA/cm 2 .
垂直Si微型太陽能電池的表徵 Characterization of Vertical Si Micro Solar Cells
使用半導體參數分析儀(4200-CSC，Keithley)研究器件在黑暗中的電流-電壓(I-V)特性。使用太陽模擬器(Class AAA，Oriel Sol3A，Newport)在AM 1.5G照度下研究我們的太陽能電池的光伏特性。入射通量使用校準功率表來測量，並且使用NREL校準的太陽能電池(PV Measurements,Inc.)雙重檢查。使用Xe光源和在400-1100nm波長範圍內的單色器測量EQE。使用配備有110mm積分球的UV-Vis/NIR分光光度計(Cary 5000，Agilent)在400-1100nm波長上進行光學反射測量來解釋從樣品的全光反射(漫反射和鏡面反射)。 The current-voltage (I-V) characteristics of the device in the dark were investigated using a semiconductor parameter analyzer (4200-CSC, Keithley). The solar characteristics of our solar cells were studied under AM 1.5G illumination using a solar simulator (Class AAA, Oriel Sol3A, Newport). Incident flux was measured using a calibration power meter and double checked using NREL calibrated solar cells (PV Measurements, Inc.). EQE was measured using a Xe source and a monochromator in the 400-1100 nm wavelength range. The total light reflection (diffuse reflection and specular reflection) from the sample was interpreted using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) equipped with a 110 mm integrating sphere at an optical reflection measurement at a wavelength of 400-1100 nm.
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