The synthesis, crystal growth, and structural and optoelectronic characterization has been carried out for the perovskite compound CsPbBr 3 . This compound is a direct band gap semiconductor which meets most of the requirements for successful detection of X-and γ-ray radiation, such as high attenuation, high resistivity, and significant photoconductivity response, with detector resolution comparable to that of commercial, state-of-the-art materials. A structural phase transition which occurs during crystal growth at higher temperature does not seem to affect its crystal quality. Its μτ product for both hole and electron carriers is approximately equal. The μτ product for electrons is comparable to cadmium zinc telluride (CZT) and that for holes is 10 times higher than CZT.

The optical and electronic properties of Bridgman grown single crystals of the wide-bandgap semiconducting defect halide perovskites A3M2I9 (A = Cs, Rb; M = Bi, Sb) have been investigated. Intense Raman scattering was observed at room temperature for each compound, indicating high polarizability and strong electron–phonon coupling. Both low-temperature and room-temperature photoluminescence (PL) were measured for each compound. Cs3Sb2I9 and Rb3Sb2I9 have broad PL emission bands between 1.75 and 2.05 eV with peaks at 1.96 and 1.92 eV, respectively. The Cs3Bi2I9 PL spectra showed broad emission consisting of several overlapping bands in the 1.65–2.2 eV range. Evidence of strong electron–phonon coupling comparable to that of the alkali halides was observed in phonon broadening of the PL emission. Effective phonon energies obtained from temperature-dependent PL measurements were in agreement with the Raman peak energies. A model is proposed whereby electron–phonon interactions in Cs3Sb2I9, Rb3Sb2I9, and Cs3Bi2I9 induce small polarons, resulting in trapping of excitons by the lattice. The recombination of these self-trapped excitons is responsible for the broad PL emission. Rb3Bi2I9, Rb3Sb2I9, and Cs3Bi2I9 exhibit high resistivity and photoconductivity response under laser photoexcitation, indicating that these compounds possess potential as semiconductor hard radiation detector materials.

Gamma-ray detection and spectroscopy is the quantitative determination of their energy spectra, and is of critical value and critically important in diverse technological and scientific fields. Here we report an improved melt growth method for cesium lead bromide and a special detector design with asymmetrical metal electrode configuration that leads to a high performance at room temperature. As-grown centimeter-sized crystals possess extremely low impurity levels (below 10 p.p.m. for total 69 elements) and detectors achieve 3.9% energy resolution for 122 keV 57Co gamma-ray and 3.8% for 662 keV 137Cs gamma-ray. Cesium lead bromide is unique among all gamma-ray detection materials in that its hole transport properties are responsible for the high performance. The superior mobility-lifetime product for holes (1.34 × 10−3 cm2 V−1) derives mainly from the record long hole carrier lifetime (over 25 μs). The easily scalable crystal growth and high-energy resolution, highlight cesium lead bromide as an exceptional next generation material for room temperature radiation detection.

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