Zhang Baohua, Guo Fuqiang, Xue Junjun, Yang Lianhong, Zhao Yafei, Ge Mei, Cai Qing, Liu Bin, Xie Zili, Chen Dunjun, Lu Hai, Zhang Rong, Zheng Youdou
Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China.
Department of Physics, Changji College, Changji, 831100, China.
Sci Rep. 2017 Dec 18;7(1):17695. doi: 10.1038/s41598-017-18110-6.
We systematically synthesized mixed-halide hybrid perovskite CHNHPb(BrI) (0 ≤ x ≤ 1) crystals in the full composition range by a solvothermal method. The as-synthesized crystals retained cuboid shapes, and the crystalline structure transitioned from the tetragonal phase to the cubic phase with an increasing Br-ion content. The photoluminescence (PL) of CHNHPb(BrI) crystals exhibited a continuous variation from red (768 nm) to green (549 nm) with increasing the volume ratio of HBr (V%), corresponding to a variation in the bandgap from 1.61 eV to 2.26 eV. Moreover, the bandgap of the crystals changed nonlinearly as a quadratic function of x with a bowing parameter of 0.53 eV. Notably, the CHNHPb(BrI) (0.4 ≤ x ≤ 0.6) crystals exhibited obvious phase separation by prolonged illumination. The cause for the phase separation was attributed to the formation of small clusters enriched in lower-band-gap, iodide-rich and higher-band-gap, bromide-rich domains, which induced localized strain to promote halide phase separation. We also clarified the relationship between the PL features and the band structures of the crystals.
我们通过溶剂热法在整个成分范围内系统地合成了混合卤化物杂化钙钛矿CHNHPb(BrI)（0≤x≤1）晶体。合成的晶体保持长方体形状，并且随着Br离子含量的增加，晶体结构从四方相转变为立方相。CHNHPb(BrI)晶体的光致发光（PL）随着HBr体积比（V%）的增加，从红色（768nm）到绿色（549nm）呈现出连续变化，这对应于带隙从1.61eV到2.26eV的变化。此外，晶体的带隙作为x的二次函数非线性变化，弯曲参数为0.53eV。值得注意的是，CHNHPb(BrI)（0.4≤x≤0.6）晶体在长时间光照下表现出明显的相分离。相分离的原因归因于形成了富含低带隙、富碘和高带隙、富溴区域的小簇，这些小簇引起局部应变以促进卤化物相分离。我们还阐明了晶体的PL特征与能带结构之间的关系。
