High efficiency CuInSe2–(CdZn)S solar cells: fabrication, results, and analysis

Abstract

The CuInSe2 thin films for solar application are grown by physical vapor deposition in a standard evaporation system. Indium-doped high conductivity (CdZn)S is evaporated onto the CuInSe2 to form the junction. The CuInSe2–(CdZn)S devices require air heat treatments to achieve the highest efficiency. High-efficiency small-area devices exceeding 11% (87.5 mW/cm2, ELH, T = 32 °C) have been fabricated this way. The behavior of the devices cannot be described as a classical heterojunction dominated by interface recombination. Instead, current–voltage and spectral-response analysis show that the diode current transport is dominated by a Shockley–Read type of recombination model, with space–charge being the dominant recombination mechanism via midgap states, with an estimated concentration of 1014 cm−3.