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Chalcogenide Perovskites for Photovoltaics

Shengbai Zhang

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 [1], 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 [2], 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 [5] 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.

[1] Y. Y. Sun, et al., Nano Lett. 15, 581 (2015).
[2] S. Pereraa, et al., Nano Energy 22, 129 (2016).
[3] W. Meng, et al., Chem. Mater., 28, 821 (2016).
[4] S. Niu, et al., Adv. Mater. 29, 1604733 (2018).
[5] Y.-Y. Sun, et al., Nanoscale 8, 6284 (2016).

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