13.4% efficient thin-film CdS/CdTe solar cells

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Abstract
Cadmium telluride is a promising thin‐film photovoltaic material as shown by the more than 10% efficient CdS/CdTe heterojunction solar cells. In this work, thin‐film CdS/CdTe solar cells have been prepared using CdS films grown from an aqueous solution and p‐CdTe films deposited by close‐spaced sublimation (CSS). The properties of CdS films deposited from an ammonical solution of a Cd‐salt, an ammonium salt, and thiourea have been controlled by optimizing the temperature and composition of the solution. The solution‐grown CdS films have a high photoconductivity ratio, and its optical transmission is superior to that of vacuum evaporated CdS films. The properties of p‐CdTe films deposited by CSS have been optimized by controlling the temperature and composition of the source material, and the substrate temperature. The properties of CdS/CdTe heterojunctions have been studied; junction photovoltage spectroscopy is used for the qualitative comparison of junction characteristics. Solar cells of 1‐cm2 area with an AM 1.5 efficiency of 13.4% are reported.