Study on spray-pyrolyzed In2S3 thin films, targeted as electron transport layer in solar energy

Efficient electron transport layers (ETLs) play a pivotal role in the performance of solar cells. In recent years, Indium sulfide (In2S3) has been studied as a promising ETL in CuInGaS(e)2, Cu2ZnSnS(e)4, and perovskite solar cells. Despite several studies on spray-deposited In2S3, there is no complete experimental investigation on In2S3 thin films. The effect of the molar ratio of S/In and the type of indium precursor on the structural, morphological, optical, and electrical properties of sprayed-In2S3 layers has been studied. Films were characterized using x-ray diffraction, scanning electron microscopy (SEM), optical transmission (UV-Vis), Mott–Schottky analysis, four-point probe, and cyclic voltammetry measurements. The crystallinity and morphological characteristics are strongly influenced by the type of indium salt, where indium acetate precursor results in a highly porous film compared with nitrate and chloride precursors. The chloride precursor demonstrates better crystallinity and considerably lower sheet resistance. All films are n-type with a carrier concentration in the range of ∼2 × 1017 to ∼2 × 1018 cm − 3, with an indirect bandgap of 2.0 eV.