Critical condition in CuInAlSe2 solar cell absorbers

Abstract

The CuInAlSe2 (CIAS) phase offers a wide band gap which allows some adjusting in band gap energy for high solar cell efficiency. Most research design a Cu-deficient condition for more favorable electronic properties, but there is still a question about the limit of Cu-deficiency in CIAS that allows good properties of solar cell absorber. In this research, we found the critical condition of Cu defficient in CIAS by preparing and analyzing the CIAS thin film absorbers. The thin film precursors were tailored using PLD system with a certain stacking order of layer-by-layer elemental film deposition and then selenized via a solid state reaction to form CIAS phases. The prepared thin films were analyzed for their composition, structure, electrical-optical properties, and morphology. The results show that CIAS thin film absorber in Cu-deficient condition still can be performed in single phase structure until 18 at.% of Cu/CIAS with high band gap energy, high charge carrier concentration, and good morphology. In addition, CIAS composition in ~17 at. % of Cu/CIAS becomes a critical condition in having good thin film absorber properties.