Perovskite Photon-Counting Detectors: Narrowing the Field

Since the pioneering demonstration of energy-resolved X-ray detection with cesium lead bromide perovskite by Mercouri Kanatzidis and coworkers in 2013, research into lead-halide perovskites for radiation detection has expanded rapidly. Among the many perovskite compositions explored, here we argue that cesium lead bromide and formamidinium lead bromide hold the strongest potential for use as photon-counting detector materials, in high- and low-photon energy applications, respectively. We justify our argument by examining the relatively low charge carrier mobility common to perovskites, which necessitates high operating biases, conditions under which many alternative compositions undergo degradation. Furthermore, we identify that the extended attenuation length associated with Pb K-shell fluorescence will likely constrain the applicability of lead-halide perovskites to two primary regimes: (1) detection of high-energy photons under low flux and low spatial resolution, as often seen in γ-ray spectroscopy; and (2) detection of low-energy X-ray photons under high flux, where reduced device thickness and small pixel size can compensate for low charge carrier mobility without the worry of excess K-escape and Compton scattering. Advancing perovskite photon-counting detectors toward practical imaging applications calls for studies under realistic photon flux conditions, focusing on parameters such as maximum count rate, charge sharing, charge cloud size, K-escape, and bias stability.