Forth, Logan; (2021) An analysis of the inorganic Perovskite, CsPbBr3, as an x-ray detecting material. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

CsPbBr3 is one perovskite among several that have drawn a large degree of interest for their semi-conductive properties and when twinned with their relatively high atomic number, these make for ideal high energy radiation detectors. Here CsPbBr3 and CsPb(Br:I)3 are synthesised through solution growth methods, then ground and pressed into pellets for the first time, where active device layers are 1 mm thick and pixel contacts of silver or gold are deposited. Furnace melt formation of single crystals is also investigated. Photoluminescence measurements of CsPbBr3 give a bandgap ranging between 2.33–2.40 eV. Perovskite samples are left in an air environment for 300 days before being tested. Radiation sensitivity is measured by exposure to a tungsten target X-ray source operating in a range of 20–100 kVp, and measuring photocurrent generation with a focus on pixel and channel contacts of varying architecture, determining the charge collection efficiency and charge sharing between pixels. X-ray Monte Carlo simulation is developed in tandem to model the energy absorption of the Perovskite, in order to determine optimum operating conditions and assist in device design. Devices are found to exhibit sensitivities in the range of 23–170 µCGy−1cm−2 but low mu-tau values of (3.3–23)×10−6 cm2 V−1. A novel lateral pixel design is demonstrated to show indirect X-ray energy contrast. X-ray images are acquired through lateral translation of perovskite pixels, where sub-mm details are resolved through the employment of contact guarding.

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