Comparison of Zr, Bi, Ti, and Ga as metal contacts in inorganic perovskite CsPbBr3 Gamma-ray Detector

We report a performance comparison of Zr, Bi, Ti, and Ga as metal contacts on solution-grown CsPbBr3 single-crystal gamma-ray detectors. The same CsPbBr3 single crystal was repeatedly deposited with different metal contacts for the evaluation of gamma spectral performance to eliminate crystal-to-crystal variation. Leakage current as low as 2–3 nA at −200 V with detector thickness 2–3 mm was consistently achieved with Zr, Bi, Ti, and Ga as Schottky contact metal, which is comparable to the leakage current level of a commercial cadmium zinc telluride (CZT) detector. Gamma energy spectra with a prominent photopeak at 662 keV were consistently acquired with all studied metal contacts. The best resolution at 662 keV is 11% with a peak-to-Compton valley ratio of 2, indicating an improved spectrum shape than previous results. Through Americium-241 (241Am) alpha spectra acquisition, the hole mobility of the CsPbBr3 single crystal is evaluated to be 1.78 cm2 V−1 s−1. We also discussed issues related with the CsPbBr3 gamma detector architecture and interface layers, commonly encountered during CsPbBr3 gamma detector fabrication, that is, impact of electron/hole transport layer and surface oxide layer on gamma detector spectral performance, comparison of different metal–perovskite–metal structures. The persistent CsPbBr3 gamma spectral performance marks the good reproducibility of CsPbBr3 gamma detectors, further enabling CsPbBr3 detector field applications.