ZnxCd1−xS films suitable for use in solar cells have been formed by simultaneous evaporating of ZnS and CdS. Lattice parameter and band gap are found to change almost linearly with composition. Electrical resistivity increases from <1 to ≳1010Ω cm as x increases from 0 to 1. Nonseries-resistance-limited ZnxCd1−xS-CuyS photovoltaic cells have exhibited open-circuit voltages greater than 0.7 V, apparently due to a better match between the ZnxCd1−xS and CuyS electron affinities.

Changes in the electrical sheet resistance and optical density of copper-sulfide (Cu x S) films have been measured as functions of thermal aging in air. It was found that sheet resistance (or bulk resistivity) and optical density (or absorption coefficient) both initially increase with aging, and subsequently decrease. Maximum bulk resistivity and absorption coefficient values, corresponding to the chalcocite phase of CuxS, were found to be about 0.1 !lcm and 5X 10 4 cm-I (at 1.8 eV photon energy), respectively. CdS/CuxS solarcell short-circuit current and efficiency were monitored as functions of thermal aging time, degradation being directly related to CU x S sheet resistance. The dependence of sheet resistance on CU x S stoichiometry is discussed. Several possible mechanisms are proposed to account for the observed behavior.

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1. Low-frequency resistance can be dominated by contacts. It was found that silver paint contacts were roughly equivalent to metal contacts bonded during vulcanization. 2. Three electrical regimes are clearly evident, determined by loading: dielectric, percolation, and conducting. 3. Resistance and dielectric constant dispersion for loading above 30 phr agree with Kawamoto's model. 4. Each carbon-black loading results in a distinctive dispersion signature. 5. Dynamic conductivity can be used to delineate persistent and transient carbon-black-structure changes versus composition, DSA, frequency, and potentially other parameters (temperature, stress waveform, etc.). 6. The remaining conductive network during stress is represented by gmin; Δg is determined by network fracture and reformation; gmin−gα is proportional to the amount of remaining transient structure; g0−gα is proportional to the total transient structure; normalized conductivity Z is the remaining-to-total transient-structure ratio. 7. The Δgm=0.525(g0−gα) relation indicates that maximum reformation occurs when approximately half the transient structure is broken down and confirms the correlation between conductivity parameters and transient carbon-black structure.

Cadmium stannate (Cd2SnO4) films of 112 per square sheet resistance and 85% average transmissivity (500-650 nm) have been grown by means of rf sputtering onto silica substrates. CdS-Cu2S thin film solar cells with conversion efficiencies greater than 5% for front and rear illumination have been fabricated. The reflection of transmitted light back through the cell has increased the light generated current. Fabrication techniques are described and current-voltage and spectral response measurements are presented for frontwall and backwall modes of operation.