Photoelectrical Properties of PbS-CdSe Double Layer Vapour Deposit Film

The evaporation temperatures of PbS and CdSe in a vacuum of 5 × 10^<-5> mmHg were obtained experimentally, they are 650℃ and 700℃ respectively. Spectral responses of PbS-CdSe double layer vapour deposit cells and PbS-CdSe mixed vapour deposit cells were obtained experimentally. In the case of PbS-CdSe mixed vapour deposit cells, the spectral response when a mono chromatic light falls on the surface of the cell agrees with the spectral response when the monochromatic light falls on the back of the cell. This may be the evidence of no stratiform distribution of PbS and CdSe in mixed vapour deposit cells. In the case of double layer vapour deposit cells, the spectral response in a near infrared region is improved when the monochromatic light falls on the PbS layer while the spectral response in the visible region is improved when the monochromatic light falls on the CdSe layer. When a PbS layer is vapor deposited firstly, it should be covered by a CdSe layer which will be vapour deposited secondly, so the PbS layer can not be oxidized sufficiently through heating treatment and the photoelectrical sensitivity of the PbS layer is low. When a PbS layer is vapour deposited secondly on a CdSe layer, the PbS layer is enough oxidized and the photoelectrical sensitivity of the PbS layer is high. In the case of PbS-CdSe mixed vapour deposit cells, there is some difference between the spectral response when the substrate used is a frosted glass plate and the spectral response when the substrate used is a plane glass plate. The cause of this difference may be a difference in the oxidation degree of PbS microcrystals due to the layer structure. The model of PbS-CdSe mixed vapour deposit layer is proposed and the results of an aging test of the photoelectrical sensitivity of PbS-CdSe mixed vapour deposit cells and PbS-CdSe double layer vapour deposit cells are presented.