The property of materials could vary greatly under pressure. For example, we have uncovered that the semiconductor PbTe has a high-pressure-tuned metastable structure that can be retained at ambient conditions. This showed, for the first time, a reversal of a so-called Hall-Petch relation, relating the structural stability to particle size (10.1021/nl203409s), raising a possibility that PbTe semiconductor materials could someday serve a host of useful technological applications, such as thermo-electronics, energy conversion, etc. We also focused the pressure-dependent study on hybrid perovskites, a class of current state-of-the-art photovoltaic materials. We observed pressure-induced crystallographic transitions and band-gap tuning of MAPbI₃ (MA = methylammonium) through collaboration with research groups from NTU and CalTech (10.1002/adma.201705017; 10.1002/anie.201601788). A later publication also discussed the case of FAPbI₃ (10.1021/jacs.8b09316). Since the pressure-induced band-gap variation significantly affects the power conversion efficiency, an application of modest pressure could be sufficient to initiate phase changes and bandgap adjustments if the hybrid perovskite compositions are "pre-adjusted" chemically. Such a combined chemical-pressure strategy may prove valuable in the design of new perovskites for photovoltaic applications.

Further reading materials:

Nano Lett., 2011, 11(12), 5531-5536, 2011.   10.1021/nl203409s

Nanoscale, 8 (9), 5214-5218, (2016).   10.1039/C5NR08291A  

Nano. Lett. 13 (8) 3729-3735, (2013).   10.1021/nl4016705

Angew. Chem. Int. Ed. 55 (22) 6540-6544, (2016).   10.1002/anie.201601788

Adv. Mater. 30(2), 1705017, (2017).   10.1002/adma.201705017

J. Am. Chem. Soc.  140(42), 13952-13957 (2018).   10.1021/jacs.8b09316

J. Am. Chem. Soc. 141 (3) 1235 - 1241, (2019).   10.1021/jacs.8b07765