Cs 2 AgBiBr 6 double perovskite recently emerges as a promising semiconductor for ionization detections because of the low detection limit and nontoxic composition. However, it suffers from unsatisfactory reproducibility and wide fluctuation of electrical properties, as also in other halide perovskite systems. Here, solubility and supersolubility are employed as quantitative indicators to direct the growth of Cs 2 AgBiBr 6 single crystals. The optimized Cs 2 AgBiBr 6 crystals exhibit smooth surface as well as high resistivity with narrow distribution from 6.10 × 10 9 to 3.31 × 10 10 Ω cm, in contrast to the unoptimized Cs 2 AgBiBr 6 crystals ranging from 6.04 × 10 7 to 5.61 × 10 9 Ω cm. Moreover, the fabricated X-ray detector has a sensitivity of 1974 µC Gy air −1 cm −2 under 50 V mm −1 electric field, which is close to lead halide perovskite detectors. This study highlights the importance of quantitative understanding about the growth process, and might also be applicable to other crystal growth methods, for instance, antisolvent or solvent evaporation method.
Sensitive X-ray detection is crucial for medical diagnosis, industrial inspection and scientific research. The recently described hybrid lead halide perovskites have demonstrated low-cost fabrication and outstanding performance for direct X-ray detection, but they all contain toxic Pb in a soluble form. Here, we report sensitive X-ray detectors using solution-processed double perovskite Cs 2 AgBiBr 6 single crystals. Through thermal annealing and surface treatment, we largely eliminate Ag + /Bi 3+ disordering and improve the crystal resistivity, resulting in a detector with a minimum detectable dose rate as low as 59.7 nGy air s −1 , comparable to the latest record of 0.036 μGy air s −1 using CH 3 NH 3 PbBr 3 single crystals. Suppressed ion migration in Cs 2 AgBiBr 6 permits relatively large external bias, guaranteeing efficient charge collection without a substantial increase in noise current and thus enabling the low detection limit.
Weinan Yuan,Guangda Niu,Yeming Xian,Haodi Wu,Huamin Wang,Hang Yin,Peng Liu,Wenzhe Li,Jiandong Fan
The double perovskite Cs 2 AgBiBr 6 single crystal holds great potential for detecting applications because of its low minimum detectable dose rate and toxic-free merit. Nevertheless, the disordered arrangement of Ag + /Bi 3+ usually gives rise to unexpected structural distortion and thereafter heavily influences the photoelectric properties of the Cs 2 AgBiBr 6 single crystal. Herein, phenylethylamine bromide is demonstrated to be capable of in situ regulation of the order–disorder phase transition in the Cs 2 AgBiBr 6 single crystal. The improved ordering extent of alternatively arranged [AgX 6 ] 5− and [BiX 6 ] 3− octahedra is theoretically and experimentally proven to decrease the defect density and suppress self-trapped exciton formation, and thereby tune the band gap and enhance the carrier mobility, which consequently promotes its application in an X-ray detector. The performance of a corresponding detector based on PEA-Cs 2 AgBiBr 6 single crystal displays superior performances, e.g., longer carrier drift distance, higher photoconductive gain, and faster current response (13 vs 3190 µs). Prominently, the as-fabricated PEA-Cs 2 AgBiBr 6 single-crystal X-ray detector has an extremely high sensitivity with a value of 288.8 µC Gy air −1 cm −2 under a bias of 50 V (22.7 V mm −1 ), which largely outperforms those of their counterparts with lower ordering structure.
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