Bell Telephone Laboratories

Sigurd Wagner

Joseph Leo Shay

Ernest Buehler

Klaus Jurgen Bachmann

Benjamin Tell

Horst Manfred Kasper

Gary D Boyd

John George Bergman, Jr

Fred Wudl

Ravinder Kumar Jain

Manfred Hermann Bettini

Assunta Anna Pritchard

Sarat K Mohapatra

Piero Migliorato

Solid state electrochromic devices are fabricated using, as the electrochromic material, ionic conductors such as heteropoly acids. The properties of the ionic conductors permit construction of a device having only two electrodes and the electrochromic material. In operation, low voltages impressed between the electrodes induce a color change. For example, when phosphotungstic acid is employed, the color change is from white to dark blue. Cycle times as low as 100 msec are achievable and the devices exhibit memory properties.

Solid 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

Liquid-semiconductor photocells have received much attention recently as candidates for use in solar power conversion devices. A semiconductor liquid junction photovoltaic cell having a photoactive electrode made from CuInS.sub.2 and a liquid electrolyte containing a redox couple consisting of S.sub.2 .dbd./S.dbd. anions has been found to produce a stable photocurrent output.

Semiconductor liquid junction photocell using a CuInS.sub.2  electrode

Ionic conductivity in ternary chalcogenides of the form AB.sub.x C.sub.y, where A is a metallic atom with atomic number no greater than 55 which has a +1 oxidation state, B is a group III A metallic atom and C is a group VI A atom, has been observed. This ionic conductivity makes the compounds useful as components in electrochemical cells, e.g., electrolytes and electrodes.

Ternary ionic conductors

Devices which emit in the visible region having a metal oxide barrier layer, e.g. magnesium oxide or beryllium oxide, and having a corresponding metal electrode, i.e., a magnesium or beryllium electrode, in addition to a silver electrode are stable at room temperature. The emitted light spectrum is dependent on the voltage applied to the device which emits an orange or green appearing light for the Mg and Be junctions, respectively.

Light emitting tunnel junctions which are stable at room temperature

Electrochemical device comprising ternary ionic conductors

A process for polishing both the cadmium and sulfur face of CdS using buffered HCl solutions has been found to produce very smooth crystal surfaces. Use of HCl solutions buffered to a pH between 2.2 and 2.8 to polish the cadmium face is quite effective. An equally effective polishing agent for the sulfur face is a HCl solution buffered to a pH between 0.7 and 1.3.

Polishing of CdS crystals

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

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.

Growing community of inventors

Holmdel, NJ, United States of America

Sigurd Wagner