Bell Telephone Laboratories

Klaus Jurgen Bachmann

Joseph Leo Shay

Sigurd Wagner

Ernest Buehler

Paul H Schmidt

Arthur D Pearson

Hans-Joachim Lewerenz

Arthur R Tynes

Edward G Spencer

Karnamadakala Sreenivasaacharlu Harsha

Charles T Ryan

Suzanne Rose Nagel

Maria T Menezes

Manfred Hermann Bettini

Photovoltaic devices are fabricated by forming a thin passivating layer, for example, an oxide layer on a semiconductor material. The passivating layer on the semiconductor material is then contacted with an electrolyte such as an electrolyte containing vanadium ions. The resulting electrolyte/passivating layer/semiconductor (EPLS) structure exhibits excellent solar conversion efficiencies and good stability.

Photoelectrochemical cells

Devices based on InAs.sub.1-x P.sub.x where 0.85.ltoreq.x&lt;1 show advantageous properties. An exemplary device is a rectifying diode formed from indium tin oxide deposited on the subject InAs.sub.1-x P.sub.x.

Indium phosphide arsenide based devices

Opto-electronic devices such as photodetectors have been made based on bulk crystals of Ga.sub.x In.sub.1-x P.sub.y As.sub.1-y. These bulk crystals have high purity, e.g., less than 10.sup.16 carriers/cm.sup.3 and low defect densities, e.g., less than 10.sup.6 cm.sup.-2. The properties of these crystals lead to photodetectors with good quantum efficiencies.

Opto-electronic devices based on bulk crystals of complex semiconductors

Devices using a transparent conductive layer of indium oxide or indium tin oxide, and a layer of a direct gap semiconductor material have been found to operate as solar cells and as light emitting devices. Exemplary of such devices is an indium tin oxide/p-InP cell which shows a 12.5% solar power conversion efficiency and also emits a red colored light when biased.

Metal oxide/indium phosphide devices

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

Glass fiber optical-waveguides consisting of a metal oxide-silicate glass core and silica cladding are produced according to the invention by means of a metal evaporation technique. An evacuated fused silica tube containing an evaporated metal deposit is heated to temperatures sufficient to form a uniform metal silicide layer on its inner surface. This layer is then oxidized and reacted with the silica tubing at elevated temperatures to form a metal oxide-silica glass layer. The tube is then collapsed to give a solid rod preform with a metal oxide-silica glass core. Fibers drawn from such preforms exhibit a graded refractive index profile and low loss. The details of the fabrication technique are described, and a representative loss spectrum is presented.

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Piscataway, NJ, United States of America

Klaus Jurgen Bachmann