School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052, Australia.
School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052, Australia.
J Colloid Interface Sci. 2017 Oct 15;504:586-592. doi: 10.1016/j.jcis.2017.06.017. Epub 2017 Jun 7.
Cesium lead halide (CsPbX, X=Cl, Br, I) perovskites are a new material system that has attracted a lot of research focus. Its tunable band gap and better thermal stability than organic lead halide perovskite give it the potential for applications in optoelectronic devices such as light-emitting diodes and solar cells. Here we have synthesized CsPbBrI perovskite quantum dots (QDs) via a solution process, and then have selected three different anti-solvents to purify the product. A significant effect on optical properties of CsPbBrI was found after the centrifugation process. Up to a ∼40nm shift was observed in mixed halide CsPbBrI QDs in both absorbance and PL spectra after purification while there was no obvious change in pure CsPbBr when it was subjected to the same purification steps. XPS analysis shows that the Br:I ratio of the CsPbBrI QDs had changed as a result of exposure to the anti-solvent, causing the change of the band gap and shift of the spectra. It is also shown that iodine can be removed more easily than bromine during the anti-solvent purification. Ab-initio simulations of small CsPbBrI atomic clusters suggest that exposed Cs ions on Cs-terminated facets are the first species to be attacked by hydrophilic molecules, likely dragging halide ions into solution with them to maintain overall charge neutrality in the material. Charge carrier recombination rates were found to be unchanged and all samples maintained a good PL quantum yield which was more than 44%.
铯铅卤（CsPbX，X=Cl，Br，I）钙钛矿是一种新材料体系，引起了广泛的研究关注。它可调的带隙和比有机铅卤钙钛矿更好的热稳定性，使它有可能在光电设备中得到应用，如发光二极管和太阳能电池。在这里，我们通过溶液法合成了 CsPbBrI 钙钛矿量子点（QDs），然后选择了三种不同的抗溶剂来纯化产物。我们发现离心过程对 CsPbBrI 的光学性质有显著影响。在纯化后，混合卤化物 CsPbBrI QDs 的吸收光谱和光致发光（PL）光谱中观察到高达约 40nm 的位移，而纯 CsPbBr 在经过相同的纯化步骤后没有明显变化。X 射线光电子能谱（XPS）分析表明，由于暴露于抗溶剂，CsPbBrI QDs 的 Br:I 比例发生了变化，导致带隙变化和光谱位移。结果还表明，在抗溶剂纯化过程中，碘比溴更容易被去除。小 CsPbBrI 原子团簇的从头算模拟表明，在 Cs 端终止晶面上暴露的 Cs 离子是首先被亲水分子攻击的物种，可能会将卤化物离子拖入溶液中，以保持材料的整体电中性。载流子复合率保持不变，所有样品都保持了良好的 PL 量子产率，超过 44%。
