Tuning the Interfacial Dipole Moment of Spacer Cations for Charge Extraction in Efficient and Ultrastable Perovskite Solar Cells
Yuankun Qiu, Jianghu Liang, Zhanfei Zhang, Zihao Deng, Heng Xu, Maosheng He, Jianli Wang, Yajuan Yang, Lingti Kong, Chun‐Chao Chen
Abstract
The two-dimensional (2D)/three-dimensional (3D) heterojunction perovskite solar cell (PSC) has recently been recognized as a promising photovoltaic structure for achieving high efficiency and long-term stability. Rational design of the 2D spacer cation is important to achieve a win–win situation for defects’ passivation and photogenerated carrier extraction. Herein, we carry out first-principles calculation to analyze the dipole moment of phenethylamine-type molecules and their resulting 2D/3D perovskites. Based on the results of theoretical calculation, the dipole moment of 2D cations can be well tuned by varying the number of fluorine atoms on the para-position of the benzene ring, which further determines the interfacial dipole across the 2D/3D heterojunction interface. A high dipole 2D perovskite layer at the interface between the 3D perovskite and hole-transporting material is found to promote charge transport and suppress charge trapping efficiently. As a result, our 2D/3D PSCs exhibit a champion power conversion efficiency over 22% and a fill factor over 83%. Moreover, our solar cells also show a remarkable stability, maintaining 80% of its initial efficiency for more than 1400 h without encapsulation under a 30 ± 5% relative humidity.