Judicious Molecular Design of 5<i>H</i>‑Dithieno[3,2‑b:2′,3′‑d]Pyran‐based Hole‐Transporting Materials for Highly Efficient and Stable Perovskite Solar Cells
Kun‐Mu Lee, Chia‐Hui Lin, Chia‐Chi Chang, Tingyu Yang, Wei‐Hao Chiu, Wei‐Chen Chu, Ya‐Ho Chang, Sie‐Rong Li, Shih‐I Lu, Hsiao‐Chi Hsieh, Kang‐Ling Liau, Changwei Hu, Chih‐Hung Chen, Yun‐Shuo Liu, Wei‐Chun Chou, Mandy M. Lee, Shih‐Sheng Sun, Yu‐Tai Tao, Yan‐Duo Lin
Abstract
Abstract The structural modification of hole‐transporting materials (HTMs) is an effective strategy for enhancing photovoltaic performance in perovskite solar cells (PSCs). Herein, a series of dithienopyran (DTP)‐based HTMs ( Me‐H , Ph‐H , CF3‐H , CF3‐mF , and CF3‐oF ) is designed and synthesized by substituting different functional groups on the DTP unit and are used fabricating PSCs. In comparison with Me‐H having two methyl substituents on the dithienopyrano ring, the Ph‐H having two phenyl substituents on the ring exhibits higher PCEs. Notably, the incorporation of trifluoromethyl groups in CF3‐H endows the molecule with a larger dipole moment, deeper HOMO energy level, better film morphology, closer molecular stacking, more efficient defect‐passivation, enhanced hydrophobicity, and better photovoltaic performance when compared with the Ph‐H counterpart. Furthermore, the HTMs of CF3‐mF and CF3‐oF , which feature fluorine‐substituted triphenylamine, demonstrated excellent film‐forming properties, more suitable energy levels, enhanced charge mobility, and improved passivation of the buried interface between HTMs and perovskite. As a result, PSCs employing CF3‐mF and CF3‐oF gave impressive PCEs of 23.41 and 24.13%, respectively. In addition, the large‐area (1.00 cm 2 ) PSCs based on CF3‐oF achieved a PCE of 22.31%. Moreover, the PSCs devices with CF3 series HTMs exhibited excellent long‐term stability under different conditions.