Exploring the PbS-Bi2S3 Series for Next Generation Energy Conversion Materials

Abstract

As photovoltaics become an ever more important part of the global energy economy, the search for inexpensive, earth-abundant solar absorbers has grown rapidly. The binary compounds PbS and Bi2S3 have both seen success in previous photovoltaic studies; however, bulk PbS has a small band gap, restricting its efficiency, and Bi2S3, while strongly absorbing, can be limited by its layered structure. The mixed PbS-Bi2S3 series has previously been the focus of mostly structural studies, so in this article, we examine the electronic structure of the known members of this series using hybrid density functional theory. We find that the lead bismuth sulfides are able to retain optimal properties, such as low carrier effective masses and strong absorption, from both parent phases, with band gaps between 0.25 and 1.32 eV. PbBi2S4 emerges from our computational screening as a possible earth-abundant solar absorber, with a predicted maximum efficiency of 26% at a film thickness of 0.2 μm and with the retention of the three-dimensional connectivity of lead and bismuth polyhedra.