Recent studies have shed light on metal halide perovskites’ interesting properties for direct X-ray detection in medical imaging [1]. Unlike scintillators usually used for medical radiography, semiconductors can directly convert X-ray photons into electric signals, paving the way for higher sensitivity with better spatial resolution. Thanks to their good charge carrier transport properties and process versability, perovskite materials are attracting growing attention for detection applications, and among them, CsPbBr3 is particularly studied [1,2], due to its high atomic number that allows good X-ray absorption. To this end, we have developed a scalable sublimation method to grow hundreds of µm-thick polycrystalline layers of CsPbBr3 [3].

               While CsPbBr3 performance is promising, its charge-carrier transport properties remain poorly understood. A better comprehension could give insight to improve signal-to-noise ratio, which is the key parameter to build a good detector. This work presents a preliminary study of those properties (carrier concentration, mobilities and material type) through two characterization methods: Hall effect measurements and laser Time of Flight (ToF) measurements.

               Hall effect measurements provide the majority carrier concentration and mobility, and the material type. To overcome perovskites’ modest carriers’ densities and mobilities, an AC field is used, to get the signal out of the noise through lock-in detection [4]. Furthermore, adding an illumination source generates more carriers thus providing a more stable signal [4,5]. Measurements conducted with and without illumination showed low mobilities around 10 cm² V^-1 s^-1 and low majority carrier concentration around 10⁹ cm^-3, in good agreement with literature data on perovskites [6]. A single crystal was also probed for comparison purposes, revealing similar results.

               Mobilities of both carriers can also be extracted with ToF measurements, which probe the transport inside the bulk [7]. With an above-bandgap energy laser, electron-hole pairs are generated and one type of carriers can be collected on the opposite electrode by applying a high electric field. The signals obtained on CsPbBr₃ polycrystalline layers revealed similar mobilities for both carriers around 30 cm² V^-1s^-1, consistent with prior Hall effect measurements.