State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Nanotechnology. 2019 Apr 19;30(16):165402. doi: 10.1088/1361-6528/aafeb6. Epub 2019 Feb 13.
Pristine and Br-doped HN = CHNHPb(I Br ) (FAPb(I Br ), Br content x = 0, 0.05, 0.15, 0.2, 0.3, and 0.4) films were prepared. The effect of Br-doping on phase stability, defect density, and performance of FAPb(I Br ) was investigated by x-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible-near infrared absorbance spectroscopy, x-ray photoemission spectroscopy (XPS), Kelvin probe force microscopy (KPFM), positron annihilation spectroscopy, and current density-voltage (J-V) characteristics. The XRD measurements exhibit the enhancement of perovskite phase stability at x = 0.05. However, the phase stability decreases gradually with Br content (x) over 0.05. The increase of Br-doping content leads to the downshifting of both valence band (VB) position (indicated by XPS) and Fermi level (illustrated by KPFM). The energy level shifts are most probably due to the increase of Br 4p orbital content in VB and the change of self-doping levels. Doppler broadening spectra of positron annihilation radiation of the samples reveal that, the defect densities of Br-doped samples are much lower than that of pristine FAPbI. For FAPb(IBr) sample, a high photoelectric conversion efficiency of 17.12% (25.7% higher than that of undoped sample) is successfully achieved. The significant enhancement of photoelectric conversion efficiency realized by Br-doping is attributed to the improvement of morphology, high phase stability, and low defect densities.
pristine 和 Br 掺杂的 HN = CHNHPb(I Br ) (FAPb(I Br )，Br 含量 x = 0，0.05，0.15，0.2，0.3 和 0.4) 薄膜被制备。通过 X 射线衍射（XRD）、扫描电子显微镜、紫外-可见-近红外吸收光谱、X 射线光电子能谱（XPS）、开尔文探针力显微镜（KPFM）、正电子湮没谱和电流密度-电压（J-V）特性研究了 Br 掺杂对 FAPb(I Br )的相稳定性、缺陷密度和性能的影响。XRD 测量结果表明，在 x = 0.05 时，钙钛矿相稳定性增强。然而，随着 Br 掺杂量（x）超过 0.05，相稳定性逐渐降低。Br 掺杂含量的增加导致价带（VB）位置（由 XPS 表示）和费米能级（由 KPFM 表示）向下移动。能级移动很可能是由于 VB 中 Br 4p 轨道含量的增加和自掺杂能级的变化。样品的正电子湮没辐射多普勒展宽谱表明，Br 掺杂样品的缺陷密度远低于原始 FAPbI。对于 FAPb(IBr) 样品，成功实现了 17.12%的高光光电转换效率（比未掺杂样品高 25.7%）。通过 Br 掺杂实现的光电转换效率的显著提高归因于形态的改善、高相稳定性和低缺陷密度。
