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 CsPbBr 3 single-crystal gamma-ray detectors. The same CsPbBr 3 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 ( 241 Am) alpha spectra acquisition, the hole mobility of the CsPbBr 3 single crystal is evaluated to be 1.78 cm 2 V -1 s -1 . We also discussed issues related with the CsPbBr 3 gamma detector architecture and interface layers, commonly encountered during CsPbBr 3 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 CsPbBr 3 gamma spectral performance marks the good reproducibility of CsPbBr 3 gamma detectors, further enabling CsPbBr 3 detector field applications.