γ-RayPIN Diodes Made of CH3NH3PbBr3 PerovskiteSingle Crystals Assistedwith Highly Doped Epitaxial Layers

MAPbBr3 (MA = CH3NH3) perovskite single-crystal γ-ray detectors based on Schottky diodes typically suffer from electrochemical reactions at the cathode under an applied bias. A low-resistance contact could decrease the electrical field near metal/MAPbBr3 single crystals. However, it is difficult to achieve highly conductive n-type/p-type layers made of MAPbBr3 single crystals. In this work, we report that n-type and p-type MAPbBr3 can be achieved by incorporating heterovalent dopants and adjusting the MABr:PbBr2 molar ratio. Through epitaxial growth, γ-ray PIN diodes consisting of n-type and p-type layers are fabricated, which establish sufficient energy barriers. The resulting γ-ray PIN diode (8.4 × 8.5 × 4.1 mm3) exhibits a dark current of only 238 nA under a bias of −1000 V. Owing to the absence of a strong electric field near the cathode, cathode stability is improved. The balanced charge transport property is further confirmed by time-of-flight and Hecht analyses. The γ-ray PIN diode achieves an energy resolution of 3.1% for 662 keV γ-ray photons.