Engineering the charge extraction and trap states of Sb2S3 solar cells

Abstract

Antimony sulfide (Sb2S3) as a binary chalcogenide has emerged as a promising candidate for next-generation thin-film photovoltaics. Although breakthroughs have been made in terms of device performance in recent years, the power conversion efficiency is still far from the Shockley–Queisser limit. It is mainly attributed to the poor charge transport and abundant defects, which deteriorate the fill factor and result in grievous open-circuit voltage loss. Here, we improved the device performance through a synergetic approach: (i) by introducing ZnSnO3 as the second electron transport layer, the current leakage was effectively reduced, and the charge extraction was enhanced; then, (ii) the prepared Sb2S3 films were treated via a low-temperature and short-time post-treatment with thiourea, which significantly suppressed the carrier recombination and increased the open-circuit voltage. More importantly, we systematically analyzed the trap features of the Sb2S3 films with/without treatment, mainly including the trap density, trap level, and trap capture cross section. We found that defects near the surface due to elemental inhomogeneity by the hydrothermal method could be effectively passivated, and defect-assisted recombination was suppressed after the thiourea treatment.