Organic-inorganic halide perovskites (OIHPs) bring an unprecedented opportunity for radiation detection with their defecttolerance nature, large mobility-lifetime product, and simple crystal growth from solution. Here we report a dopant compensation in alloyed OIHP single crystals to overcome limitations of device noise and charge collection, enabling -ray spectrum collection at room temperature. CH₃NH₃PbBr₃ and CH₃NH₃PbCl₃ are found to be p-type and n-type doped, respectively, whereas dopant-compensated CH₃NH₃PbBr_2.94Cl_0.06 alloy has over tenfold improved bulk resistivity of 3.6×10⁹ φcm. Alloying also increases the hole mobility to 560 cm² V^-1 s^-1, yielding a high mobility-lifetime product of 1.8×10^-2 cm² V^-1. The use of a guard ring electrode in the detector reduces the crystal surface leakage current and device dark current. A distinguishable ¹³⁷Cs energy spectrum with comparable or better resolution than standard scintillator detectors is collected under a small electric field of 1.8Vmm^-1 at room temperature.

In view of its band gap of 2.2 eV and its stability, methylammonium lead bromide (MAPbBr₃) is a possible candidate to serve as a light absorber in a subcell of a multijunction solar cell. Using complementary temperature-dependent time-resolved microwave conductance (TRMC) and photoluminescence (TRPL) measurements, we demonstrate that the exciton yield increases with lower temperature at the expense of the charge carrier generation yield. The low-energy emission at around 580 nm in the cubic phase and the second broad emission peak at 622 nm in the orthorhombic phase originate from radiative recombination of charges trapped in defects with mobile countercharges. We present a kinetic model describing both the decay in conductance as well as the slow ingrowth of the TRPL. Knowledge of defect states at the surface of various crystal phases is of interest to reach higher open-circuit voltages in MAPbBr₃-based cells.