Chlorination effects of a non-fullerene acceptor based on a selenium heterocyclic core for high-efficiency organic solar cells

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2023-02, Vol.11 (8), p.32-329
• Main Authors: Feng, Hao, Meng, Xianglin, Fu, Liying, Liu, Chunbo, Yin, Xinxing, Zhu, Enwei, Li, Zaifang, Che, Guangbo
• Format: Article
• Language: English
• Subjects: Chlorination; Chlorine; Circuits; Energy levels; Fullerenes; Hole mobility; Molecular orbitals; Molecular structure; Photovoltaic cells; Selenium; Short circuit currents; Solar cells
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc05333k

A selenium substitution strategy combined with terminal modulation for developing high-efficiency non-fullerene acceptors (NFAs) has drawn much attention in the field of organic solar cells (OSCs). Herein, three novel NFAs featuring a benzoselenadiazole central core and IC terminal groups, namely BTSeIC-2Cl-γ , BTSeIC-2Cl-mix and BTSeIC-4Cl , were successfully designed and synthesized by modulating the numbers and positions of the chlorine atoms. Compared to the two counterpart NFAs bearing a single chlorinated γ-position and mixed positions (β or γ-position) on the IC group, di-chlorinated NFA BTSeIC-4Cl shows the strongest absorption, the shallowest lowest unoccupied molecular orbital energy level and the best molecular packing among the three acceptors. Consequently, the PM6: BTSeIC-4Cl based device exhibits a champion PCE of 16.14% with a short-circuit current density ( J SC ) of 26.92 mA cm −2 , which is mainly attributed to it having the most balanced and highest electron/hole mobility and optimal blend morphology. It is worth mentioning that the obtained J SC of the PM6: BTSeIC-4Cl device is among the highest values reported for selenium-heterocyclic fused-ring acceptors with chlorinated terminal groups in the OSCs. Furthermore, the acceptor BTSeIC-2Cl-γ with a defined molecular structure achieved a better PCE of 14.91% due to its higher charge mobility and stronger π-π interaction, whereas the acceptor BTSeIC-2Cl-mix exhibited a PCE of 14.21%. This work shows that combining the selenium-heterocyclic core with the halogen-substituted regulation of terminal groups is an effective way to produce high-performance NFAs. The photovoltaic performance of three chlorinated NFAs based on a selenium heterocyclic core (namely BTSeIC-2Cl-γ , BTSeIC-2Cl-mix and BTSeIC-4Cl ) were researched by precisely regulating the number and position of end-group chlorine atoms.