Structural, optical and electrical properties of Cu2FeSnSe4 and Cu(In,Al)Se2 thin films

Abstract

Cu-based semiconductors Cu2FeSnSe4 (CFTSe) and Cu(In, Al)Se2 (CIAS) have been fabricated using radio-frequency magnetron sputtering combined with rapid thermal selenization processing. For CFTSe, the heating rate ranging from 60 to 150°C/min results in a difference in structure, morphology and optical properties. Thin film exhibits a pure phase structure, smooth surface and a band gap of 1.19eV as the heating rate elevated to 90°C/min. Furthermore, the CFTSe thin film selenized at 90°C/min own the smallest value of cell volume compared with the others samples, which represents a more stable structure. In terms of the other Cu-based material CIAS, three different selenization pressures, i.e., 1, 5 and 10Torr, have been employed for CIAS preparation. Thin film transforms into single phase with dense morphology along with the pressure of 1Torr. The diverse band gap of CIAS thin films from 1.34 to 2.18eV attribute to two reasons: (i) the various Al content will affect the hybridization degree of Al–Se, and finally tunes the band structure, (ii) amounts of CuSe has a certain degree of effect on the band gap of the CIAS. In addition, the electrical properties of CFTSe and CIAS are also researched with the open circuit voltage (Voc) of 94 and 365mV, respectively, signifying potential applications of CFTSe and CIAS for the thin film solar cells.