Electrochemical photovoltaic cells CdSe thin film electrodes. Quarterly progress report No. 1, June-August 1979

The overall objective of this program is to obtain AM1 efficiencies in the range of 10% with electrochemical cells utilizing thin film electrodes. The system currently being investigated is the CdSe/aqueous sulfide-polysulfide system. This report presents the results to date of the initial CdSe deposition parameter study. The key finding has been that the ratio of Se and Cd in the as deposited film has marked effect on the film's chemical, microstructural, optical, and electrical properties as well as I-V performance. In addition, it has been found that electrolyte concentration and compostion can have a strong effect on the I-V performance of a given electrode

Electrochemical photovoltaic cells CdSe thin film electrodes. Final report, June 1979-June 1980

Progress on developing stable, thin-film CdSe electrodes with sunlight conversion efficiency of 10% for use with aqueous polysulfide electrolytes in frontwall and backwall illuminated EPCs is reported. The main effort has been directed towards establishing the relationships among thin-film processing, resultant electronic properties and I-V performance in order to produce electrodes with maximum power conversion efficiency. The most encouraging results have been obtained with CdSe thin-film electrodes produced in two ways for frontwall cells. Films were deposited on titanium at approximately 100/sup 0/C with a high Se/Cd ratio and then heat treated in air at 350 to 400/sup 0/C. These films usually have a very fine grained microstructure after heat treatment and the resultant electrodes exhibit fairly square I-V characteristics with fill factors of 0.6 or greater and high current output. The overall power efficiency of these electrodes is limited by relatively low output voltages. At present, power conversion efficiencies of 3 to 5% can be obtained reproducibly at simulated AM2 conditions with electrodes processed in this manner. The second type of film that has yielded very promising results is deposited on titanium at substrate temperatures greater than 400/sup 0/C. The interesting feature of these electrodes is their increased open circuit voltage. However, the current output and fill factor are lower. As a result, the power conversion efficiency of these electrodes is 3 to 4%. Backwall electrodes with an efficiency of greater than 4% and short circuit densities near theoretical for AM2 conditions have been produced

In situ XANES study of the valence state of chromium during electrochemical polarization of AlCr alloys

The chemistry of chromium in the passive film on pure chromium and sputtered AlCr thin films has been studied in situ in an electrochemical cell under potential control using XANES. Depending on the rate of potential increase, the 6-valent chromium can dissolve from the alloy or be trapped in the passive film where it is electroactive i.e. the valence state can be reversibly switched between the 3- and 6-valent states by switching the applied potential. The kinetics of these processes were investigated