Zhou Wencai, Chen Xiaoqing, Zhou Rongkun, Cai Hongbo, Wang Yun, Zhang Tiankai, Zheng Zilong, Gao Feng, Zhang Yongzhe, Yan Hui
The Faculty of Materials and Manufacturing, Faculty of Information Technology, Beijing University of Technology, Beijing, 100124, China.
Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, 58183, Sweden.
Small. 2024 Aug;20(32):e2310368. doi: 10.1002/smll.202310368. Epub 2024 Mar 21.
Grain boundaries (GBs) have a significant role in polycrystalline perovskite solar cells (PSCs). However, there is ongoing debate regarding the impact of GBs on the performance and long-term stability of PSCs. Employing the first-principles molecular dynamics for perovskites, the iodine vacancy defect migrations both in bulk and at GBs are investigated. i) The positive iodine vacancy (V ) is found that have both lower formation energy (1.4 eV) and activation energy (0.18 eV) than those of neutral iodine vacancy (V), statistically. It indicated the V acts as the dominant migrated iodine vacancy rather than V; ii) the iodine vacancy at GBs has ≈0.48 eV higher activation energy than those in bulk, which leads to the accumulation of iodine vacancy at GBs; iii) the presence of V result in a 3-fold increase in charge recombination ratio at GBs, compared to pristine PSCs. Based on quantum molecular dynamics statistical results, which are consistent with experimental measurements, insights into iodine vacancy migration both at GBs and in the bulk are gained. This understanding can be valuable for defects engineering related to ion migration, in order to improve the long-term stability and promote the performance of PSCs.
晶界在多晶钙钛矿太阳能电池（PSC）中起着重要作用。然而，关于晶界对PSC性能和长期稳定性的影响仍存在争议。利用钙钛矿的第一性原理分子动力学，研究了碘空位缺陷在体相和晶界处的迁移情况。i）统计发现，正碘空位（V ）的形成能（1.4 eV）和活化能（0.18 eV）均低于中性碘空位（V）。这表明V 是主要的迁移碘空位而非V；ii）晶界处的碘空位活化能比体相中的高约0.48 eV，这导致碘空位在晶界处积累；iii）与原始PSC相比，V 的存在导致晶界处的电荷复合率增加了3倍。基于与实验测量结果一致的量子分子动力学统计结果，深入了解了碘空位在晶界和体相中的迁移情况。这种认识对于与离子迁移相关的缺陷工程很有价值，有助于提高PSC的长期稳定性并提升其性能。
