Interstitial Copper Doping in Cs3Bi2Br9: A Pathway to Enhanced Radiation Detection Performance

The modulation of double perovskites via a cation transmutation approach is a viable strategy to enhance their optoelectronic performance. Here, we explored the cation transmutation approach by substituting Ag with Cu in double halide perovskites and investigated the role of Cu in X-ray detection performance. We observe that Cu does not incorporate in a double halide perovskite structure (Cs2CuBiBr6 does not form), rather resulting in interstitial dopants in its pristine Cs3Bi2Br9 structure. We demonstrate the impact of Cu dopants on X-ray and α-particle detection and find that Cu dopants lead to elevated sensitivity and reduced limit of detection along with prolonged stability under continuous X-ray exposure. It also exhibits remarkable performance under high-energy photon irradiation from a 6 MV clinical linear accelerator, suggesting potential cancer treatment applications. Interstitial Cu+ ions are expected to interact with negatively charged defects in Cs3Bi2Br9, neutralizing them and promoting carrier delocalization, which enhances carrier transport. Our results shed light on the modulation of bismuth halide perovskites and show that these lead-free perovskite detectors are viable options for dosimetry in radiotherapy, medical imaging, and industrial applications, including in remote regions with limited resources and power restrictions.