A-site Cation Engineering for Highly Efficient MAPbI3 Single-Crystal X-ray Detector.

Metal halide perovskites have emerged as a new generation of X-ray detector materials. However, large-sized MAPbI3 single crystals (SCs) still exhibit lower performance than MAPbBr3 SCs in X-ray detection. DFT (density functional theory) simulations suggest the problem could be overcome by alloying large-sized cations at the A site. The alloyed process could notably decrease the electron-phonon coupling strength and increase the material defect formation energy. Accordingly, centimeter-sized alloyed DMAMAPbI3 (DMA=dimethylammonium) and GAMAPbI3 (GA=guanidinium) SCs are obtained. Electrical characterizations confirm the GAMAPbI3 SCs display improved charge collection efficiency. It also exhibits a remarkable reduction of dark current, an important figure of merit for X-ray detectors. With a judiciously designed device architecture, the overall detector performance confirms GAMAPbI3 SCs as one of the most sensitive perovskite X-ray detectors to date.