Photovoltaic cell with thin CdS layer

摘要

The photovoltaic panel of the present invention is initially formed with a CdS and CdTe layers in overlying relationship on a glass substrate and the effective thickness of the CdS layer is reduced during a two-step annealing process to both form larger diameter CdTe crystals (36A, 36B, 36C, 36D) and substantially reduced thickness CdS layer (32) by diffusion into the CdTe layer (44) such that majority of sunlight having a wavelength less than 520 nm passes through the CdS layer (32) to the photovoltaic junction. The p-type CdTe material (44) is first heat treated in an oxidizing environment to oxidize impurities and thereby substantially enhance the desired electrical properties of the p-type CdTe material. The heat treated material is then annealed in a substantially inert environment to increase crystal sizes and thereby enhance photovoltaic efficiency. During the heat treating step, an oxidation gradient may be maintained through the thickness of the p-type CdTe layer (44).