Structure and properties of high efficiency ZnO/CdZnS/CuInGaSe2 solar cells

Thin-film polycrystalline solar cells with the structure ZnO/CdZnS /CuInGaSe2 fabricated with total area efficiencies of up to 12.5 percent under AM1.5 equivalent illumination and 10.5 percent under AM0 equivalent are discussed. These are among the highest total area efficiencies reported for polycrystalline thin-film solar cells. Current- voltage and quantum efficiency data for such a high-efficiency cell are given. Described are the deposition of the CuInGaSe2 by physical vapor deposition in vacuum, the CdZnS by chemical deposition from solution, and the ZnO by reactive sputtering. The electrical and optical properties of the individual layers have been inferred from measurements on complete devices and on separate witness layers. Optical constants and thicknesses obtained for the device layers from these measurements are presented, and the requirements for optimizing the device efficiency are discussed. (I.E.)