Centimeter-sized inorganic lead halide perovskite CsPbBr₃ crystals grown by an improved solution method

As a member of the lead-halide perovskite family, inorganic perovskite CsPbBr₃ exhibits excellent optical and electrical properties with higher stability to the environment. However, former efforts to obtain large-size CsPbBr₃ single crystals with satisfactory quality using low temperature solution methods reached limited results. In this work, we have studied the growth of CsPbBr₃ crystals using the antisolvent vapor-assisted crystallization (AVC) method. By adjusting the mole ratio of PbBr2 and CsBr, the phase diagram of the final products is acquired. Five regions are identified, including the Cs₄PbBr₆ single phase region, Cs₄PbBr₆ and CsPbBr₃ two phases region, CsPbBr₃ single phase region, CsPbBr₃ and PbBr2· 2[(CH₃)₂SO] metastable two phases region, and CsPbBr₃ and PbBr2·2[(CH₃)₂SO] two phases region. Three methods are adopted to improve the size and crystalline quality of CsPbBr₃. The growth rate is effectively tailored by diluting the antisolvent MeOH solution using DMSO to reduce the MeOH vapor pressure. Centimeter-size bright CsPbBr₃ crystals have been obtained. The room temperature bandgap of CsPbBr₃ is estimated at ∼2.29 eV by the transmission spectra. The photoluminescence spectra show two strong emission peaks, located at 530 and 555 nm, respectively, which are related to the free and bond excitons. The resistivity is as large as 2.1 × 109 Ω· cm. Hall effect measurements demonstrate the CsPbBr₃ is p-type conductivity with a hole carrier concentration of 4.55 × 107 cm^-3 and the mobility of 143 cm² V^-1 s^-1. The resulting Au/CsPbBr₃/Au device exhibits strong photoresponse to optical light, with an on-off ratio of two orders under a light emitting diode (∼1 mW/cm2) with a wavelength of 365-420 nm. Our research would shed more light on the growth and the photoresponse properties of CsPbBr₃ crystals.