Photodiodes based on a MAPbBr3/Bi3+-doped MAPbCl3 single crystals heterojunction for the X-ray detection

Perovskite single crystals (PSCs) can be used to fabricate high performance photoelectric detectors due to their superior optoelectronic characteristics. Generally, an external electric field needs to be applied in PSC-based detectors to improve their charge collection efficiency. However, the large external electric field increases the dark current, which will enlarge the noise current. To alleviate this drawback, an approach of fabricating a PSC-based heterojunction is proposed in this work, which contributes to reduced dark current in a relatively high reverse electric field. In this study, a heterojunction formed by epitaxially growing MAPbBr3 PSCs on Bi3+-doped MAPbCl3 PSCs is reported, and it shows relatively low trap density and higher built-in potential. The as-fabricated Au-MAPbBr3/Bi3+-doped MAPbCl3 PSC heterojunction-Au photodiode shows smaller dark current density, better long-term current stability and reduced noise level by approximately four orders compared to the Au–MAPbBr3 PSCs–Au photoconductor device under an external reverse voltage of 100 V (mean electric field of ∼31.5 V mm−1). Moreover, the pN heterojunction photodiode shows favorable X-ray detection performance, with a fast response time of 4.89 μs and high sensitivity of 1.72 × 103 μC Gyair−1 cm−2 for 50 kVp X-ray photons under a reverse electric field of 31.5 V mm−1. This work confirms that the epitaxial fabrication of PSC heterojunctions may be a promising strategy to enhance the performance of X-ray photodetectors.