Title: Sb2S3 thin films by ultrasonic spray: Formation and application in solar cells

Abstract

Sb2S3 with bandgap of 1,7 eV, absorption coefficient 1.105 cm-1 at 450 nm and good stability makes it prime candidate for application as top cell absorber in tandem solar cells or in semitransparent solar cells. In this study rapid, scalable and robust in-air deposition method of ultrasonic spray pyrolysis (USP) has been applied to grow phase pure Sb2S3 thin films. SbCl3- thiourea complex and antimony xanthate were used as precursor materials. Thermal analysis study (TG/DTA –EGA-MS) of precursors was performed to study the thermal decomposition reactions and determine the suitable range of temperatures for Sb2S3 film deposition. Two-stage process where continuous amorphous film with uniform thickness is grown by USP at temperatures around 200˚C followed by annealing in an inert atmosphere for 5 minutes results in polycrystalline single phase Sb2S3 as confirmed by XRD, Raman and EDX study. Using SbCl3-thiourea based precursor the optimal film deposition temperature is 210˚C, in case antimony xanthate Sb2S3 amorphous film could be grown even at lower temperature (160-180˚C) but measures to avoid oxidation during the film growth should be considered. It was shown that an excess of thioamides in spray solution is effective to depress the formation of oxide phase. Thin film solar cells with structure TCO/TiO2/Sb2S3/HTM with all component layers prepared by solution methods in air, showed conversion efficiency of 5.5 % at AM1.5G. The effect of Sb2S3 absorber layer thickness and type of HTM layer on solar cell output parameters will be discussed.