Bell Telephone Laboratories

Joseph Leo Shay

Gerardo Beni

Sigurd Wagner

Ernest Buehler

Klaus Jurgen Bachmann

Lawrence M Schiavone

William C Dautremont-Smith

Wilbur Dexter Johnston, Jr

Horst Manfred Kasper

James D McIntyre

Shimshon Gottesfeld

Piero Migliorato

Catherine E Rice

Manfred Hermann Bettini

Electrochromic devices based on anion transfer have been made. These devices utilize an iridium oxide electrochromic electrode in conjunction with an electrolyte that provides a source of anions with formula weight in the range 18 to 33.

Electrochromic device

Electrochromic devices based on electrochromic iridium oxide electrodes are disclosed. These electrodes are iridium oxide entities produced by vacuum deposition techniques such as by sputtering from an iridium target in the presence of an oxygen atmosphere. All solid state electrochromic devices utilizing such electrodes are possible.

Iridium oxide based electrochromic devices

It is possible to significantly increase the efficiency of the electrolysis of water into hydrogen and oxygen while maintaining stability of the anode. This efficiency increase is obtained by using an iridium oxide anode which is produced by vacuum deposition techniques.

Electrolytic process useful for the electrolysis of water

Electrochromic devices based on anodic iridium oxide as the electrochromic material have been made. These devices exhibit long term stability, memory, and good response times, e.g., less than 80 msec. for reflectivity changes of about 70% (50 msec. for 50% changes). Devices using an anodic iridium oxide film immersed in a sulfate electrolyte have been operated for more than 6.times.10.sup.5 coloration/bleaching cycles at 0.5 Hz without noticeable change in properties. Response times and stability are also improved by a heat treatment of the anodic iridium oxide at temperatures between 40 and 100 degrees C.

Heat treated electrochromic devices

The voltage produced by a photovolatic device containing a semiconductor layer is enhanced by interfacing the semiconductor material of the device with an additional semiconductor material to form an isotype heterodiode. For example, the solar power conversion efficiency and the voltage produced by an n-CdS layer immersed in an electrolyte is enhanced by interfacing the n-CdS layer with an n-GaAs layer.

Semiconductor devices with enhanced properties

Heterodiodes showing excellent potential for use in solar cells and photoelectric devices consist of junctions of p-type indium phosphide and n-type cadmium sulfide. These heterojunctions can be formed either from single crystal or from polycrystalline semiconductor material. The former type junction when incorporated in a solar cell exhibits promise for applications such as in space vehicles. The latter type junction as used in a solar cell has potential for large scale power generation. A chemical vapor deposition process for producing polycrystalline p-type indium phosphide films for incorporation into such a power producing device is disclosed.

Solar cells and photovoltaic devices of InP/CdS

Electrical contact between a conducting substrate, e.g., graphite, and a polycrystalline semiconductor layer of, for example p-type indium phosphide in a semiconductor device is made through a p-type GaAs intermediary layer. The GaAs layer is deposited on the conducting substrate by conventional methods such as chemical vapor deposition. The indium phosphide layer can then be deposited on the GaAs by similar techniques. The specific resistance and blocking voltage of such an interface is typically below 2 .OMEGA.-cm.sup.2 and 50 millivolts respectively. The efficiency of a p-InP/nCdS solar cell containing the improved electrical contact is measurably increased.

GaAs layers as contacts to thin film semiconductor layers

A hydrogen transport process for cleaning the surface of an indium or gallium based semiconductor material and for depositing n-type cadmium sulfide on the cleaned semiconductor material is disclosed. The cleaning and deposition can be accomplished in sequence or simultaneously. The process entails adding hydrogen sulfide to a hydrogen gas flow in a chemical vapor deposition process. Single crystalline photovoltaic cells of p-InP/n-CdS with a 13.5% efficiency have been reproducibly fabricated. An efficiency of 4.6% has been obtained with a thin layer polycrystalline p-InP/n-CdS cell. Additionally, a p-GaAs/n-CdS heterodiode cell has been produced.

Etching of III-V semiconductor materials with H.sub.2 S in the

Solar cells showing improved efficiency, amounting to about 14 percent for overall solar power conversion, are obtained by annealing InP/CdS solar cells in a slightly reducing atmosphere for about 15 minutes in a temperature range preferably from about 550.degree. centrigrade to about 600.degree. centigrade. In an annealing temperature range from 400.degree. centigrade to 625.degree. centigrade, an inversely dependent adjustment of annealing time is found desirable. The atmosphere preferably comprises mainly a substantially inert component and typically comprises an H.sub.2 + N.sub.2 mixture, such as forming gas (15% H.sub.2 + 85% N.sub.2).

Annealing solar cells of InP/CdS

Photovoltaic devices are constructed from a principal body of copper indium selenide (CuInSe.sub.2) upon which is deposited a hetero-epitaxial layer of a high bandgap semiconductor, such as an n-type layer of cadmium sulfide (CdS). When made with a high-resistance intermediate region, the device is a photovoltaic detector for modulated radiation and has a response time as low as 5 nsec for a reverse bias of approximately two to three volts. When made without a high-resistance intermediate region (e.g., an abrupt p-n heterojunction) the device is a useful solar cell. In these forms of the device, absolute photovoltaic quantum efficiencies up to 70 percent have been observed. The quantum efficiency of the solar cell type of device is reasonably flat between 0.55 and 1.25 .mu.m. With forward bias, the device is a light-emitting diode with external electro-luminescent quantum efficiency of .about.1.times.10.sup.-.sup.4 at room temperature and .about.1.times.10.sup.-.sup.2 at 77.degree.K, liquid nitrogen temperature.

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Marlboro, NJ, United States of America

Joseph Leo Shay