GaAs photovoltaic cell

FIQURE 7-27 Relative response of various types of photoelectric transducers (A-G) and heat transducers (H. I) A, photomultiplier tube B, CdS photoconductivity C, GaAs photovoltaic cell D, CdSe photoconductivity cell E, Se/SeO photovoltaic ceii F, siiicon photodiode G, PbS photoconductivity H, thermocouple /, Golay cell. (Adapted from R W. Druse, L. N. MoGlauchlih, and R. B. Quistan, Elements of Infrared Technology, pp. 424-25, New York Wiley, 1962. Reprinted by permission of John Wiley Sons Inc.)... 

Fig. 5. Efficiency improvements in photovoltaic cells where ( ) corresponds to GaAs (—) InP ( ) CdS ( ) CdTe ( ) amorphous siUcon and...

Langmuir ME, Parker MA, Rauh MD (1982) Electrochemical photovoltaic cells based on n-GaAs and the triiodide/iodide redox couple in acetonitrile. J Electrochem Soc 129 1705-1710... 

The theoretical solar conversion efficiency of a regenerative photovoltaic cell with a semiconductor photoelectrode therefore depends on the model used to describe the thermodynamic and kinetic energy losses. The CE values, which consider all the mentioned losses can generally only be estimated the full line in Fig. 5.65 represents such an approximation. Unfortunately, the materials possessing nearly the optimum absorption properties (Si, InP, and GaAs) are handicapped by their photocorrosion sensitivity and high price. 

At present, the only photochemical storage system which satisfies nearly all of these conditions is the reaction of photosynthesis however, certain photovoltaic cells such as the silicon and GaAs cells, satisfy many of the requirements for direct conversion to electricity. In addition, there are several possible systems which have a potential to satisfy most of the requirements and will be considered in this article. 

So-called wet solar cells show promise, particularly because of their relative ease of fabrication. In this type of photovoltaic cell, the junction is formed, between a semiconductor and a liquid electrolyte. No doping is required because a junction forms spontaneously when a suitable semiconductor, such as GaAs, is contacted with a suitable electrolyte, Three knotty problems (accelerated oxidation of surface of semiconductor exchange of ions between semiconductor and electrolyte forming a blocking layer and deposition of ions of impurities on the surface of the semiconductor) all have been solved and thus the concept now appears technically viable,... 

II-VI semiconductor layers and bulk semiconductors like Si, GaAs, InP, etc. In particular, quantum wells are formed by thin epitaxial multilayered structures like (Zn, Cd)Se/ZnS. Nevertheless, the choice between bulk semiconductors and the layers deposited or between the multilayers is governed by the lattice mismatch between the two components as the lattice mismatch causes the formation of misfit dislocations. In the optical devices these defects are potential non-radiative centres and at worst they can cause the failure of injection lasers. Figure 29 is a map of energy gap versus lattice constants for a variety of semiconductors it can be used to select different heterostructures, not only for optoelectronics applications but also for photovoltaic cells. In the latter application the deposited films are generally polycrystalline and the growth of high-quality epitaxial layers has received little applications. 

The hierarchy of photovoltaic cell efficiencies is presented in Table 1. Semiconductor effects, such as recombination, reduce the power efficiency of a GaAs-based device from a value of 37%, based solely upon band gap, to 15.3%. Reflection losses, with an... 

General Status and Prognosis for Electrochemical Photovoltaic Cells. The main thrusts of research activities in EP Cells are in thin film electrodes, new layered compounds, non-aqueous electrodes, and storage systems. Work on thin film electrodes is concentrating on electrodeposited, thermally evaporated, or chemical-vapor-deposited thin films of CdSe, CdTe, GaAs, and CdSex Tej[ x (40). Research on new layered compounds is primarily devoted... 

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