Chalcogenide Perovskites for Photovoltaics
Department of Physics, Applied Physics and Astronomy,
Rensselaer Polytechnic Institute, Troy, New York, 12180, USA
Halide perovskites have recently emerged as a star in low-cost photovoltaics, but their low stability and the toxicity of Pb pose serious concerns. Chalcogenide perovskites ABX3 (where A and B represent 2+ and 4+ cations, respectively, and X represents either S or Se) are, on the other hand, friendlier to environment and more stable, and hence could be a good alternative to the halides. According to first-principles calculations , CaZrSe3 has a direct band gap of 1.35 eV, which is ideal for solar cells. Moreover, chalcogenides, like halides, have superior optical absorption properties compared to other well-known and mature solar-cell materials. Our experimental partners have experimentally synthesized several chalcongenide perovskites and made optical measurements , which validates the theory. In particular, the combined optical absorption and PL measurements suggest that BaZrS3 is a direct gap material with a band gap of about 1.7 eV that can be continuously tuned to 2.9 eV by forming oxychalcogenides. Other recent experimental studies of the chalcongenide perovskites also confirm our predictions [3,4]. Mixing organic-inorganic hybrid perovskites by a split-anion approach (to group-VI + group-VII elements) is another alternative to halide perovskites. We show  that such a splitting may offer an unusual combination between indirect band gap for long carrier lifetime and high optical absorption for efficient solar harvesting, which could be superb for photovoltaics.
 Y. Y. Sun, et al., Nano Lett. 15, 581 (2015).
 S. Pereraa, et al., Nano Energy 22, 129 (2016).
 W. Meng, et al., Chem. Mater., 28, 821 (2016).
 S. Niu, et al., Adv. Mater. 29, 1604733 (2017).
 Y.-Y. Sun, et al., Nanoscale 8, 6284 (2016).