Spacer Engineering Using Aromatic Formamidinium in 2D/3D Hybrid Perovskites for Highly Efficient Solar Cells
Tingting Liu, Jiahao Guo, Di Lu, Zhiyuan Xu, Qiang Fu, Nan Zheng, Zengqi Xie, Xiangjian Wan, Xiaodan Zhang, Yongsheng Liu, Yongsheng Chen
Abstract
Organic spacers play an important role in 2D/3D hybrid perovskites, which could combine the advantages of high stability of 2D perovskites and high efficiency of 3D perovskites. Here, a class of aromatic formamidiniums (ArFA) was developed as spacers for 2D/3D perovskites. It is found that the bulky aromatic spacer ArFA in 2D/3D perovskites could induce better crystalline growth and orientation, reduce the defect states, and enlarge spatially resolved carrier lifetime thanks to the multiple NH···I hydrogen-bonding interactions between ArFA and inorganic [PbI6]4– layers. As a result, compared to the control device with efficiency of 19.02%, the 2D/3D perovskite device based on such an optimized organic salt, namely benzamidine hydrochloride (PhFACl), exhibits a dramatically improved efficiency of 22.39% along with improved long-term thermal stability under 80 °C over 1400 h. Importantly, a champion efficiency of 23.36% was further demonstrated through device engineering for PhFACl-based 2D/3D perovskite solar cells. These results indicate the great potential of this class of ArFA spacers in highly efficient 2D/3D perovskite solar cells.