Angewandte Chemie | 2019
A-site Cation Engineering for Highly Efficient MAPbI3 Single Crystal X-ray Detector.
Abstract
Metal halide perovskites have emerged as a new generation of X-ray detect materials of great promise. However, large-sized MAPbI3 single crystals (SCs) still exhibit lower performance compared to MAPbBr3 SCs in X-ray detection. DFT (density functional theory) simulations suggest the problem could be overcome by alloying large-sized cations at A site. The alloyed process could notably decrease the electron-phonon coupling strength and increase the materials defect formation energy. Accordingly, centimeter-sized alloyed DMAMAPbI3 (DMA = dimethylammonium) and GAMAPbI3 (GA = guanidinium) SCs were successfully obtained. Electrical characterizations confirm the alloyed GAMAPbI3 SCs display notably improved charge collection efficiency. Furthermore, it also exhibits remarkble reduction of dark current, which is another most important figure of merit for X-ray detectors. With judiciously designed device architecture, a high detect sensitivity, 2.3 ×104 μC Gyair-1 cm-2, is achieved for GAMAPbI3 SCs. The value represents one order of magnitude increment in detect sensitivity than the state-of-the-art MAPbI3 SCs detectors. Meanwhile, the lowest detectable dose rate of 16.9 nGyair s-1 was obtained, which is more than three orders of magnitude better than the best published results obtained for MAPbI3 SCs X-ray detectors, and are on par with those reported for MAPbBr3 SCs. The overall detect performance confirms GAMAPbI3 SCs to be one of the most sensitive perovskite X-ray detectors to date.