GB2028290A

GB2028290A - Electrochromic layers of tungsten and/or molybdenum oxide

Info

Publication number: GB2028290A
Application number: GB7921059A
Authority: GB
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1978-06-28
Filing date: 1979-06-18
Publication date: 1980-03-05
Also published as: FR2430028B1; DE2828332B2; DE2828332A1; GB2028290B; FR2430028A1; IT7968153A0; ES481372A1; JPS556000A; IT1165209B; SE7905645L; DE2828332C3; SE447311B

Abstract

An electrochromic layer containing of WO3 and/or MoO3, preferably in amounts of at least 10% by weight, has an increased crystallisation resistance provided by at least one additional component which has a stabilising effect in relation to crystallisation and very little or no effect upon the electrochromic behaviour of the layer. The component may be selected from P2O5, B2O3, Al2O3, SiO2As2O3, Sb2O3 GeO2 In2O3, SnO2, SeO2 TeO2, TiO2, ZrO2, ZnO, CdO, rare earth (lanthanide) series, alkaline earch metal oxides and mixtures thereof.

Description

SPECIFICATION Electrochromic layers with increased crystallisation resistance The invention relates to electrochromic layers with increased crystallation resistance.

German Auslegeschrift No. 1589429 discloses an electrochromic (EC) arrangement which has an active layer consisting of oxides of polyvalent transition metals, such as for example, amorphous W03 or MoO3 or mixtures of both oxides. Such an electrochromic arrangement may be used for the purpose of transmission or reflection electrical control, since the electrically induced optical absorption, whose maximum lies in the near IR (~1000no) may also remain extremely high in the visible spectrum range. As the crystallinity of the active layer increases, the absorption maximum shifts into the further IR, and the visibly perceptible optical effects become increasingly weak.

Electrochromic layers can be applied in various manners, such as for instance high vacuum volatilisation, cathode atomising, pyrolytic or hydrolytic reaction.

Amorphous WO3 or MoO3 layers or mixed W03/MoO3 layers crystallise on tempering, as the free energy of the crystalline condition is smaller than that of the amorphous condition. The crystallisation temperature of the layer is also a measure of its resistance to crystallisation. The normal electro-optical operation of an EC-system also leads to crystal formation and growth in the active layer, since the migration of ions provides continuous shocks in the amorphous lattice to seek out energetically more favourable positions for the more or less random-arranged layer modules.

The purpose of the present invention to to achieve layers of increased crystallisation-resistance. This is achieved according to the invention, in that components are incorporated in the active layer which, on the one hand, have a network-formation effect but, on the other hand, have a co-ordination tendency which is different from the original layer modules, thus raising the "vitrification ability" of the layer, so that the known stability of glasses may also be achieved in the event of thermal stressing.

So-called netword-formers, ensuring a network of polyhedrons which is the basis of glass formation, are known in the glass industry. On the other hand, it is completely new and unexpected that the integration of networkformers in the active layer should have little or no prejudicial effect on electrochromic properties.

Already a relatively limited network-former content of, for instance, 1% by weight of P203 considerably assists in the stabilisation of the layer structure, without reaching the lower limits at which the effect is noted.

Active layers with a relatively high network-former content of for example, 80% by weight of SlO2 + P205 will still show EC-properties. On the other hand, their optical values change more slowly than in pure WO3-layers as a result of the reduced ion-and electron conductivity, though it may be important in certain applications to have a high temperature resistance - and thus a high crystallisation resistance - though without high speed in electrochromic performance.

Suitable stabilising components are as follows:- P205, B203, Al203, SiO2, As203, Sb203, GeO2, In203, SnO2, SeO2, TeO2, TiO2, ZrO2, ZnO, CdO, rare earth series, alkaline earth metal oxides and mixtures of these components.

Preferably, the layer contains at least 10% by weight of WO3 and/or MoO3. The layer may be produced by high vacuum volatilisation of a WO3- and/or MoO3- bearing glass; cathodic atomisation of a glass or sinter target containing WO3 and/or MoO3; pyrolytic transformation of suitable metal-oganic compounds from the vapour phase; or hydrolytic transformation of suitable inorganic or metal organic compounds from the fluid phase.

Three examples of layers according to the present invention and their advantageous operation are described below: Example 1 A sintered mixture of 1% by weight P205 and 99% by weight WO3 are volatilised by electron beam radiation. The volatilisation is effected under a pressure of < 1 x 10-4 mbars and a volatilisation rate of 10 nm/s. On reaching a layer thickness of 500 nm on the substrate-glasses with a conductive SnO2-ln203 layer the volatilisation process is stopped. The electrochromic behaviour and the crystallation temperature of the sample 1 thus obtained are determined in an electrochemical cell with wet electrolyte.

Example 2 A prefused glass consisting of 20% by weight P203 and 80% by weight WO3 is volatilised by electron beam radiation. Volatilisation is effected at a pressure of < 1 x 10-4 mbars and a volatilisation rate of 10 nm/s. On reaching a layer thickness of 500 nm on the substrate - glasses with conductive SnO2-l N203 layer - the volatilisation is stopped. The electrochromic performance and the crystallisation temperature of the sample 2 thus obtained is then determined as outlined above.

Example 3 A sintered mixture of 30% by weight B203 and 70% by weight WO3 is volatilised by means of electron beam radiation. The volatilisation is effected at a pressure of /1.10-4 mbar and a volatilisation rate of 10 nm/s. On reaching a layer thickness of 500 nm on the substrate -glass with conductive SnO2-ln203 layer - the volatilisation is stopped. The electrochromic performance and the crystallisation temperature of the sample 3 thus obtained is determined as above.

The electrochromic performance is tested by electron injection from the conductive layer and simultaneous injection of H+ - ions from a dilute H2S04 acid into the active layer. The comparison is then made with an unstabilised 500 nm thick W03 layer on an equally conductive coated glass substrate (sample 4).

The depth of colouration and speed of colouration under equal charges are determined. A diffraction analysis is carried outto determine if any crystallisation has occurred.

Comparative test results Sample No.

1 2 3 4 EC-performance before toughening v. good v. good v. good v. good crystallisation after toughening none none none minimal 1 h in air at 300 C EC-performance after 1 h at 300"C v. good v. good v. good moderate crystallisation after toughening none none none heavy 1 h in air at 350"C EC-performance after 1 h at 350"C good good good poor crystallisation after toughening none none none not 1 h in air at 400"C checked EC-performance not after 1 h at 400"C good good good checked

Claims

1. An electrochromic layer with increased crystallisation resistance, containing in addition to WO3 and/or MoO3 electrochromic oxides, at least one additional component having a stabilising effect in relation to crystallisation and has no or very little effect upon the electrochromic behaviour of the layer.

2. An electrochromic layer according to claim 1, wherein said at least one additional component is selected from F2O5, B203, Al203, SiO2, As203, 5B203, GeO2, In203, SnO2, SeO2, TeO2, TiO2, ZrO2, ZnO, CdO, rare earth (lanthanide) series, alkaline earth metal oxides and mixtures of these components.

3. An electrochromic layer according to claim 1 or 2, having a W03 and/or MoO3 content of at least 10% by weight.

4. An electrochromic layer according to any one of claims 1 to 3, when produced by high vacuum volatilisation of a WO3- and/or MoO3 bearing glass.

5. An electrochromic layer according to claim 1,when produced by cathodic atomisation of a glass or sinter target containing WO3, MoO3 or both.

6. An electrochromic layer according to any one of claims 1 to 3, when produced by pyrolitic transformation of suitable metal-organic compounds from the vapour-phase.

7. An electrochromic layer according to any one of claims 1 to 3, when produced by the hydrolytic transformation of suitable inorganic or metal organic compounds from the fluid phase.

8. An electrochromic layer as claimed in claim 1, substantially as hereinbefore described in any one of Examples 1 to 3.