Boosting photovoltaic performance for Sb₂S₃solar cells by ionic liquid-assisted hydrothermal synthesis

Bulk and surface trap-states in the Sb₂S₃films are considered one of the crucial energy loss mechanisms for achieving high photovoltaic performance in planar Sb₂S₃solar 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 Sb₂S₃hydrothermal precursor solution as a facile way to fabricate low-defect Sb₂S₃solar cells. Lower presence of small particles on the surface, as well as higher crystallinity are demonstrated in the BMIMHS-assisted Sb₂S₃films. Moreover, analyses of dark current density-voltageJ-Vcurves, surface photovoltage transient and intensity-modulated photocurrent spectroscopy have suggested that adding BMIMHS results in high-quality Sb₂S₃films 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 Sb₂S₃films with low-defects and improved optoelectronic properties.