PHOTODETECTION PROPERTIES OF CU2S-CDS HETEROJUNCTION SOLAR-CELLS

Cu//2S-CdS heterojunctions were made by dipping evaporated or sprayed CdS layers in a CuCl solution. The spectral responses of these cells were dependent on the illumination level and the electrical bias. When the cells were reverse biased and illuminated with CdS band gap radiation, the reverse current drastically increased. This is a consequence of the shrinking of the junction barrier width by the trapping of photoholes in the CdS space charge region by negatively charged copper centers. The reverse current, which is a Zener tunneling current, is very sensitive to this shrinking. Similar behavior was observed when the cells were forward biased; however, the enhancement of the direct current was weaker. The result is that the cells operate as a switch activated by CdS band gap radiation.