Band-Gap Narrowing and Electric Transport Regulation of Hybrid Perovskites via Pressure Engineering.

Lead-free organic-inorganic hybrid perovskites are one class of promising optoelectronic materials that have attracted much attention due to their outstanding stability and environmentally friendly nature. However, the intrinsic band gap far from the Shockley-Queisser limit and the inferior electrical properties largely limit their applicability. Here, a considerable band-gap narrowing from 2.43 to 1.64 eV with the compression rate up to 32.5% is achieved via high-pressure engineering in the lead-free hybrid perovskite MASbI. Meanwhile, the electric transport process changes from the initial interaction of both ions and electrons to only the contribution of electrons upon compression. The alteration in electrical characteristics is ascribed to the vibration limitation of organic ions and the enhanced orbital overlap, resulting from the reduction of the Sb-I bond length through pressure-induced phase transitions. This work not only systematically investigates the correlation between the structural and optoelectronic properties of MASbI but also provides a potential pathway for optimizing electrical properties in lead-free hybrid perovskites.