HALOS-BiPeX · Halogen-bonds and Semiconducting Spacers for Bismuth Perovskite X-ray Detectors

X-ray detectors are cornerstone of various sectors including health care, manufacturing, security, etc. The detector market has long relied on amorphous selenium (a-Se), cadmium telluride (CdTe), and cadmium zinc telluride (CZT). While effective, they often include inherent compromises in detection sensitivity at lower X-ray doses. At the same time, increasing use of X-ray technologies raises concerns about exposure to hazardous ionizing radiation. Recently, a new class of materials called perovskites with a unique ABX3 crystal structure has begun a new era of ultra-sensitive X-ray detectors. In a decade of time, they have already surpassed the benchmark sensitivity of the above mentioned commercial X-ray detector materials. However, the toxicity due to the presence lead and their moisture instability raised concern of their large scale deployment.In recent years, lead-free perovskite materials based on metals such as tin, copper, germanium, antimony, and bismuth have attracted significant research attention in the field of X-ray detectors. However, most suffer from low atomic numbers or oxidative instability, yielding poor X-ray sensitivity. In contrast, bismuth halide perovskites (BHPs) offered excellent X-ray attenuation due to the high atomic number of bismuth (Z = 83) and superior stability due to their rigid frameworks. Still, their sensitivity lags behind Pb-based analogues. To advance BHPs for next-generation X-ray detection, HALOS-BiPeX proposes a material re-design strategy employing semiconducting organic spacer cations and halogen bonding (XB) donor molecules. Despite their promise, integrating functional organic spacers into BHPs has been seldom explored due to crystallization challenges and low success rates. HALOS-BiPeX will leverage the SBNLab’s expertise in XB chemistry and my background in developing semiconducting spacer cation-based BHPs to address this challenge. The developed BHPs will be used to construct ultra-sensitive X-ray detectors.