Enhancing Carrier Transport Properties of Melt-grown CsPbBr₃ Single Crystals by Eliminating Inclusions

Abstract

All-inorganic perovskite CsPbBr3 has attracted intense attentions due to its inspiring optoelectronic properties and excellent stability. Growing large-size single crystals with high quality is vital both for the intrinsic property investigation and the high-performance device fabrication. Here, large-size CsPbBr3 single crystals (ϕ 30 mm × 100 mm) were grown by the modified Bridgman method. The surface morphologies of the as-grown CsPbBr3 single-crystal wafers were characterized by SEM, and inclusions with size of 1–2 μm were observed in the first-time grown crystal (labeled as CPB-1). By adopting a slower growth rate (0.2 mm/h) and cooling rate (5 °C/h) than that of CPB-1, the inclusions were eliminated in subsequent growth (labeled as CPB-2). The hole mobility-lifetime products were measured to be 3.92 × 10–3 and 1.46 × 10–2 cm2·V–1 for CPB-1 and CPB-2, respectively. The carrier mobility of CPB-2 was enhanced 1 order of magnitude from 10.1 ± 0.3 cm2·V–1·s–1 (CPB-1) to 101.3 ± 4.2 cm2·V–1·s–1 due to the elimination of inclusions. In addition, CPB-2 exhibited excellent α particles detection ability with the optimal energy resolution of 15.1% at −60 V bias. We provide an effective way to enhance the optoelectronic properties and device performance of melt-grown CsPbBr3 single crystal by preventing the formation of the inclusions.

Recent Advances and Perspectives on Powder‐Based Halide Perovskite Film Processing

“…[54] This was exploited in 2013 by Stoumpos et al and in the following years also by other groups, so that with the help of a rather complex vertical Bridgeman method, highly crystalline CsPbBr 3 ingots, often of several cm in diameter and length, could be produced (Figure 5a,b). [82,84,85] Here it became clear that both, the chemical purity of the precursors, [84] and the exact cooling procedure, [82,86] are important factors influencing the optical quality (easily recognizable by the optical clarity of the ingots), as well as the electrical properties, that is the sensitivity in γ-ray or α-particle detector configuration. [82,86] Under optimized melt-recrystallization conditions, CsPbBr 3 ingots were found to show excellent optoelectronic properties, such as extremely low trap densities in the range of 10 9 cm -3 , [85] and mobility-lifetime products in the range of 10 -2 cm 2 V -1 .…”

“…[82,84,85] Here it became clear that both, the chemical purity of the precursors, [84] and the exact cooling procedure, [82,86] are important factors influencing the optical quality (easily recognizable by the optical clarity of the ingots), as well as the electrical properties, that is the sensitivity in γ-ray or α-particle detector configuration. [82,86] Under optimized melt-recrystallization conditions, CsPbBr 3 ingots were found to show excellent optoelectronic properties, such as extremely low trap densities in the range of 10 9 cm -3 , [85] and mobility-lifetime products in the range of 10 -2 cm 2 V -1 . [86] Excellent optoelectronic properties of melt-processed CsPbBr 3 thick films used as X-ray detectors, have also been demonstrated recently by Pan et al, using a hot pressing approach.…”

“…Accordingly, a mobility-lifetime product of 1.3•10 -2 cm 2 V -1 was found, similar to corresponding values for melt-grown ingots. [86] This resulted in a record X-Ray sensitivity of 55 mC Gy air -1 cm -2 at a gain factor of 3632 under an electric field of 5 V mm -1 . [54] Almost at the same time, Matt et al demonstrated powder-based melt processing of 250 µm thick CsPbBr 3 films, [83] where in their case, the films were recrystallized with lower cooling rates in the range between 0.9 and 0.125 °C min −1 , and without a cover layer on the perovskite.…”

“…[ 82,86 ] Under optimized melt‐recrystallization conditions, CsPbBr 3 ingots were found to show excellent optoelectronic properties, such as extremely low trap densities in the range of 10 9 cm –3 , [ 85 ] and mobility‐lifetime products in the range of 10 –2 cm 2 V –1 . [ 86 ] Excellent optoelectronic properties of melt‐processed CsPbBr 3 thick films used as X‐ray detectors, have also been demonstrated recently by Pan et al., using a hot pressing approach. [ 54 ] Here, CsPbBr 3 powder was distributed onto a substrate, brought into the melt by heating to 560 °C, covered with a cover glass, and then cooled down again in a controlled manner whereby the perovskite thick film crystallized (Figure 5c).…”

“…Accordingly, a mobility‐lifetime product of 1.3∙10 –2 cm 2 V –1 was found, similar to corresponding values for melt‐grown ingots. [ 86 ] This resulted in a record X‐Ray sensitivity of 55 mC Gy air –1 cm –2 at a gain factor of 3632 under an electric field of 5 V mm –1 . [ 54 ] Almost at the same time, Matt et al.…”