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 CuInGaSðeÞ 2, Cu2ZnSnSðeÞ 4, and perovskite solar cells. Despite several studies on spraydeposited 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.