Investigation of the Optical, Structural and electrical properties of In2S3 thin films prepared by spray pyrolysis by changing indium salts under different temperatures

The Electron transport layer ETL plays an essential role in the solar cell Performance. In recent years, In2S3 has been used as ETL in photovoltaics such as CZTS, Se, CIG S, Se and Perovskite thin film solar cells. In this study, the easy and inexpensive spray pyrolysis method was used to fabricate In2S3 layers. The effect of indium salt type on the electrical, optical, structural and morphological characteristics of the as-sprayed In2S3 layers was investigated. Regarding this target, the Characterization techniques including X-ray diffraction XRD, Field emission electron microscopy FESEM equipped with elemental analysis EDS, UV-Vis spectrophotometer, Mott Schottky electrochemical analysis and four-point probe resistance analysis were used. The indium source chloride, nitrate and acetate salts has strong influence on the crystallinity and morphological properties. The layers resulted from precursor including indium acetate salt, are highly porous compared to the other two precursors. Whereas, the best crystallinity and lowest electrical surface resistivity by using the chloride salt were obtained. In addition, the surface resistance decreases dramatically with increasing substrate temperature. Although the prepared In2S3 layers all have n-type conductivity and indirect band gap of ~2 eV, the energy levels of the band structure varies by changing the Indium salt. The density of the majority carriers electrons also varies from 2.1 × 1017 cm-3 to 2.9 × 1019 cm-3. The highest carrier density is related to the sprayed layers at 420 °C consuming Indium acetate salt.