High‐Performance X‐Ray Detector Based on Liquid Diffused Separation Induced Cs3Bi2I9 Single Crystal

Abstract The recently demonstrated Cs 3 Bi 2 I 9 single crystals (SCs) exhibit superior performance for X‐ray detection. More importantly, they do not contain any toxic lead element. However, compared with lead‐halide perovskites, one challenge for the Cs 3 Bi 2 I 9 SC for X‐ray detection application is that it is difficult to prepare large‐sized and high‐quality SCs. Here, a liquid diffused separation induced crystallization (LDSC) method is employed to grow Cs 3 Bi 2 I 9 SCs for eliminating the temperature fluctuation and convection currents caused by the thermal gradient in the growth solution. The resultant Cs 3 Bi 2 I 9 SC exhibits a microstrain of 1.21 × 10 –3 , a resistivity of 1.12 × 10 9 Ω cm, a carrier mobility of 4.57 cm 2 V –1 s –1 , and a mobility‐lifetime product of 1.87 × 10 –3 cm 2 V –1 . As a result, an X‐ray detector based on the high‐quality Cs 3 Bi 2 I 9 SC exhibits an excellent dose rate linearity, a sensitivity of 964 µC Gy air –1 cm –2 , and a limit of detection (LoD) of 44.6 nGy air s –1 .