Trifluoromethylation Enables Compact 2D Linear Stacking and Improves the Efficiency and Stability of Q-PHJ Organic Solar Cells

• Published in: Small (Weinheim an der Bergstrasse, Germany) p. e2403821
• Main Authors: Qiu, Dongsheng, Xiong, Shilong, Lai, Hanjian, Wang, Yunpeng, Li, Heng, Lai, Xue, Zhu, Yiwu, He, Feng
• Format: Journal Article
• Language: English
• Published: Germany 01.07.2024
• Subjects: organic solar cells; quasiplanar heterojunction; small‐molecule acceptors; molecular packing; trifluoromethylation
• DOI: 10.1002/smll.202403821
• ISSN: 1613-6810; 1613-6829

Compared to the bulk heterojunction (BHJ) devices, the quasiplanar heterojunction (Q-PHJ) exhibits a more stable morphology and superior charge transfer performance. To achieve both high efficiency and long-term stability, it is necessary to design new materials for Q-PHJ devices. In this study, QxIC-CF and QxIC-CH are designed and synthesized for the first time. The trifluoromethylation of the central core exerts a modulatory effect on the molecular stacking pattern, leveraging the strong electrostatic potential and intermolecular interactions. Compared with QxIC-CH , the single crystal structure reveals that QxIC-CF exhibits a more compact 2D linear stacking behavior. These benefits, combined with the separated electron and hole transport channels in Q-PHJ device, lead to increased charge mobility and reduced energy loss. The devices based on D18/QxIC-CF exhibit an efficiency of 18.1%, which is the highest power conversion efficiency (PCE) for Q-PHJ to date. Additionally, the thermodynamic stability of the active layer morphology enhances the lifespan of the aforementioned devices under illumination conditions. Specifically, the T is 420 h, which is nearly twice that of the renowned Y6-based BHJ device (T = 220 h). By combining the advantages of the trifluoromethylation and Q-PHJ device, efficient and stable organic solar cell devices can be constructed.