The everlasting demanding for high-efficiency, low-cost solar electricity and lighting motivate the research on new earth-abundant and toxicity-free semiconductors. Sb and Bi based materials are relatively less explored partially because they contain s2 electron lone pairs which often leads to compounds with low crystal symmetry. In this presentation we will discuss two parts: Sb2Se3 for thin film photovoltaics and Bi based halide perovskite for lighting.
For the first part, our efforts and recent progress in Sb2Se3 photovoltaics will be presented. Binary chalcogenide Sb2Se3 has appropriate band gap and excellent optoelectronic properties, nontoxic and earth-abundant composition, and large vapor pressure enabling easy evaporation, making it a possible green alternative to CdTe. Using sprayed ZnO as the buffer layer and rapid thermal evaporation deposited Sb2Se3 as the absorber, ZnO/Sb2Se3 solar cells with certified 5.93% efficiency and outstanding stability was demonstrated1. Through a further Sb2Se3 film optimization, a further 7.6% device efficiency was achieved, but sadly using the CdS buffer layer. The new understanding of Sb2Se3 material properties and device physics will also be briefly presented in this talk.
For the second part, Bi based hybrid and all inorganic halide perovskites as a potential alternative to Pb perovskite for photoluminescence (PL) application will be presented. We investigated these materials for PL because Bi3+ is isoelectronic to Pb2+ but toxicity-free, and more importantly because Bi halide perovskites have low-dimensional crystal structure (0D, 1D or 2D) naturally enjoying a large exciton binding energy which is beneficial for lighting application. We will discuss our recent progress in the synthesis, characterization and lighting application of Bi-based perovskite nanocrystals2, with the emphasis on the Cs3Bi3Br9 nanocrystals with >50% PL yield and excellent stability.
We conclude that Sb and Bi based semiconductors, if carefully engineered to take advantage of their low crystal structure symmetry, are competitive for some optoelectronic applications.
J. Tang et. al. Nat. Energy, 2017, 2, 17046.
J. Tang et. al. Adv. Funct. Mater. 2017, in press.