Ding Yunxuan, Shen Yujie, Peng Chao, Huang Meilan, Hu P
School of Chemistry and Chemical Engineering, The Queen's University of Belfast, Belfast BT9 5AG, U.K.
J Phys Chem Lett. 2020 Oct 1;11(19):8041-8047. doi: 10.1021/acs.jpclett.0c02105. Epub 2020 Sep 11.
The localization of photogenerated electrons in photovoltaic and photocatalytic materials is crucial for reducing the electron-hole recombination rate. Here, the photogenerated electron localization is systematically investigated on the CHNHPbI (MAPbI) perovskite using first-principles calculations. It is found that under vacuum conditions, the photogenerated electron is delocalized in the MAPbI bulk as well as on the stochiometric MAPbI(001) surface with the CHNHI (MAI) termination, while it is trapped on the defect-free PbI-terminated surface. Our molecular dynamics simulations reveal that the introduction of solutions will prompt the formation of localized electronic states. The photogenerated electron is discovered to be localized on both the MAI- and PbI-terminated surfaces in the presence of solutions with different concentrations of HI, from pure water to the saturated solution. We demonstrate that the Pb-I bond weakening or breaking resulting in an unsaturated coordination of a Pb site is the prerequisite to trap the photogenerated electron.
光生电子在光伏和光催化材料中的局域化对于降低电子-空穴复合率至关重要。在此，利用第一性原理计算系统地研究了CHNHPbI（MAPbI）钙钛矿中光生电子的局域化情况。研究发现，在真空条件下，光生电子在MAPbI体相中以及具有CHNHI（MAI）端基的化学计量比MAPbI(001)表面上是离域的，而在无缺陷的PbI端基表面上则被捕获。我们的分子动力学模拟表明，引入溶液会促使局域电子态的形成。发现在从纯水到饱和溶液的不同HI浓度的溶液存在下，光生电子在MAI端基和PbI端基表面上均被局域化。我们证明，Pb-I键的减弱或断裂导致Pb位点的不饱和配位是捕获光生电子的先决条件。
