Boosting photovoltaic performance for Sb2S3 solar cells by ionic liquid-assisted hydrothermal synthesis

Bulk and surface trap-states in the Sb2S3 films are considered one of the crucial energy loss mechanisms for achieving high photovoltaic performance in planar Sb2S3 solar cells. Because ionic liquid additives offer interesting physicochemical properties to control the synthesis of inorganic material, in this work we propose the addition of 1-Butyl-3-methylimidazolium hydrogen sulfate (BMIMHS) into a Sb2S3 hydrothermal precursor solution as a facile way to fabricate low-defect Sb2S3 solar cells. Lower presence of small particles on the surface, as well as higher crystallinity are demonstrated in the BMIMHS-assisted Sb2S3 films. Moreover, analyses of dark current density-voltage J-V curves, surface photovoltage transient and intensity-modulated photocurrent spectroscopy have suggested that adding BMIMHS results in high-quality Sb2S3 films and a successful defect passivation. Consequently, the best-performing BMIMHS-assisted device exhibits a 15.4% power conversion efficiency enhancement compared to that of control device. These findings show that ionic liquid BMIMHS can effectively be used to obtain high-quality Sb2S3 films with low-defects and improved optoelectronic properties.