Zhang Mingfang, Feng Qingjie, Li Sheng, Nan Guangjun
Department of Physics, Zhejiang Normal University, Jinhua, Zhejiang, 321004, P. R. China.
Zhejiang Institute of Photoelectronics & Zhejiang Institute for Advanced Light Source, Zhejiang Normal University, Jinhua, Zhejiang, 321004, P. R. China.
Chemphyschem. 2023 Nov 16;24(22):e202300376. doi: 10.1002/cphc.202300376. Epub 2023 Sep 18.
The TiO /MAPbI (MA=CH NH ) interfaces have manifested correlation with current-voltage hysteresis in perovskite solar cells (PSCs) under light illumination conditions, but the relations between the photo-induced charge transfer and the collective polarization response of the dipolar MA cations are largely unexplored. In this work, we adopt density functional theory (DFT) and time-dependent DFT approach to study the light-triggered charge transfer across the TiO /MAPbI interfaces with MAI- and PbI-exposed terminations. It is found that regardless of the surface exposure of the MAPbI , the photo-induced charge transfer varies when going from the ground-state geometries to the excited-state configurations. Besides, thanks to the electrostatic interactions between the ends of MA cations and the photogenerated electrons, the photo-induced charge transfer across the interfaces is enhanced (weakened) by the negatively (positively) charged CH (NH ) moieties of the MA species. Resultantly, the positively charged iodine vacancies at the TiO /MAPbI interfaces tend to inhibit the charge transfer induced by light. Combining with the energy level alignment which is significantly modulated by the orientation of the MA species at the interfaces, the dipolar MA cations might be a double-edge sword for the hysteresis in PSCs with the TiO /MAPbI interfaces.
在光照条件下，TiO₂/MAPbI₃（MA = CH₃NH₃）界面已被证明与钙钛矿太阳能电池（PSC）中的电流-电压滞后相关，但光致电荷转移与偶极MA阳离子的集体极化响应之间的关系在很大程度上尚未得到探索。在这项工作中，我们采用密度泛函理论（DFT）和含时DFT方法，研究光触发的电荷在具有暴露MAI⁻和PbI₂⁻端基的TiO₂/MAPbI₃界面间的转移。研究发现，无论MAPbI₃的表面暴露情况如何，从基态几何结构到激发态构型时，光致电荷转移都会发生变化。此外，由于MA阳离子末端与光生电子之间的静电相互作用，MA物种带负（正）电荷的CH₃（NH₃）部分会增强（减弱）跨界面的光致电荷转移。结果，TiO₂/MAPbI₃界面处带正电荷的碘空位倾向于抑制光诱导的电荷转移。结合由界面处MA物种取向显著调制的能级排列，偶极MA阳离子对于具有TiO₂/MAPbI₃界面的PSC中的滞后现象可能是一把双刃剑。
