Photovoltaic Hybrid Perovskites under Pressure.

High-pressure studies on methylammonium trihaloplumbates, of general formula [CH3 NH3 ]+ PbX3 - (abbreviated MAPbX3 , where X = Cl, Br, I), and its analogues shed new light on the materials for harvesting solar energy and open new perspectives for photovoltaic science and technology. However, there are considerable discrepancies between the reported structural, calorimetric, and spectroscopic results and even between the results obtained by the same technique, for example, of X-ray diffraction. The origins of these discrepancies and possible pitfalls in the diffraction and spectroscopic studies on MAPbX3 crystals have been investigated. Several new effects revealed in this study involve phase transitions of exceptionally slow kinetics and the coexistence of phases. They strongly affect photovoltaic properties and are essential for theory, predictions, and technological applications.