Single-crystalline MAPbCl₃ thin-films for photo- and X-ray voltaics

3 eV wide bandgap methylammonium lead trichloride (MAPbCl₃) perovskites are promising for transparent solar cells, smart windows, and the internet of things (IoTs). However, it is challenging to crystallize uniform polycrystalline MAPbCl₃ thin films from solution. On the other hand, single-crystalline MAPbCl₃ can be grown as relatively uniform thin films. In this work, we demonstrate the fabrication of single-crystalline MAPbCl₃ thin films on conductive glass substrates <i>via</i> a space-confined inverse temperature crystallization (ITC). The perovskite films exhibit no emission peaks from states located deep within the bandgap, confirming a less defective perovskite bulk than its polycrystalline counterpart. The resulting perovskite solar cells (PSCs) yield an open-circuit voltage (<i>V</i> _OC) of up to 1.64 V and a high power conversion efficiency (PCE) of 1.1% under one sun irradiation. Additionally, the MAPbCl₃ is studied for its conversion of X-rays into electrical energy, <i>i.e.</i>, "X-ray-voltaics", demonstrating a <i>V</i> _OC of 0.89 V together with an output power of 3.57 μW cm^-2 at an X-ray tube voltage of 60 kV (4900 μW cm^-2).