Freezing non-radiative recombination in high-performance CsPbBr₃ single crystal x-ray detector

Though CsPbBr₃ single crystals (SCs) possess intriguing photoelectronic properties for x/γ-ray detection, the serious ion migration and high thermally activated carrier concentration at room temperature (RT), typically associated with defect states in CsPbBr₃ crystals, result in a high dark current and drift of baseline, hindering their potential applications. In this investigation, liquid nitrogen cooling is proposed to freeze deep-level defects in CsPbBr₃ SCs, thereby suppressing the ion migrations and decreasing the thermally excited carrier concentration. Utilizing photoluminescence (PL) and time-resolved PL spectra, coupled with theoretical models for photoexcitation and photoemission processes, the freezing of deep-level defects at liquid nitrogen temperature (LNT) is confirmed, which is conducive to decreasing non-radiative recombination. At LNT, the CsPbBr₃ SC exhibits a higher resistivity of 4.95 × 10¹¹ Ω cm and a higher mobility–lifetime product of 9.54 × 10⁻³ cm² V⁻¹, in contrast to the RT values of 3.86 × 10⁹ Ω cm and 3.67 × 10⁻³ cm² V⁻¹, respectively. Furthermore, the x-ray detector at LNT exhibits a high sensitivity of 9309 μC Gyair⁻¹cm⁻² and an impressively low detection limit of 0.054 nGy s⁻¹, which offers a route for obtaining highly sensitive x-ray detectors for applications including ultra-low dose radiation imaging.