Polytypes formed during the growth of metal halide perovskites can give rise to the formation of face-sharing sequences in corner-sharing octahedral networks. Here, the electronic influences of such structures, including the 6H and 12R phases, are found to be correlated with the fraction and stacking sequence of the face-sharing layers. The band gaps of polytypes feature a characteristic evolution from indirect to direct from pure hexagonal (2H) to cubic (3C) phases. Rather than arising from orbital mixing at the atomic level, a large band gap bowing of 1.96 eV in the CsPbI3 family was attributed to the long-range electronic interaction between octahedral building blocks. While retaining a high carrier velocity (∼2 × 105 m s-1), Fermi surface analysis further revealed a decrease of dimensionality from 3D to 2D in frequently observed polytypes, indicating a carrier blocking and anisotropic transport effect of hexagonal impurity phases, with consequences for their applications in solar cells and other optoelectronic devices.
CITATION STYLE
Li, Z., Park, J. S., Ganose, A. M., & Walsh, A. (2023). From Cubic to Hexagonal: Electronic Trends across Metal Halide Perovskite Polytypes. Journal of Physical Chemistry C, 127(26), 12695–12701. https://doi.org/10.1021/acs.jpcc.3c01232
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