The exploration of lead-free halide perovskites has revealed numerous halide perovskites that exhibit metal cation vacancies. These vacancies are generally considered to be detrimental to device applications because metal cation vacancies interrupt the orbital connectivity of halide perovskites, thereby reducing the electronic dimensionality. Herein, we interrogate the electronic dimensionality of halide perovskites with vacancies by investigating their structural, optical, and electrical properties at high pressure. X-ray diffraction and absorption measurements reveal that high pressures preferentially compress the vacancies of halide perovskites. This vacancy compression generally results in lower bandgaps and higher conductivities, demonstrating that electronic orbital interactions across vacancies are readily enhanced by structural compression. This work experimentally demonstrates that electronic orbital interactions indeed arise across metal cation vacancies in halide perovskites and are enhanced at high pressures, such that halide perovskites with vacancies offer unique optoelectronic properties at both ambient pressure and high pressure.

Enhancing orbital interactions across vacancies in halide perovskites using high pressure

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