Improving Photovoltaic Performance of All‐Polymer Solar Cells by Adding an Amorphous B←N Embedded Polymer as the Third Component.

Currently, most of the disclosed ternary strategies to improve photovoltaic performance of all‐polymer solar cells (all‐PSCs) commonly focus on the guest polymers having similar structures with the host polymer donors or acceptors. Herein, this work develops a distinctive ternary method that adding an amorphous B←N embedded polymer named BN‐Cl‐2fT to a crystallized host polymer blend of PM6 (a commercialized polymer donor) and PY‐TT (a copolymer of Y6 and thieno[3,2‐b]thiophene). Although the structures between BN‐Cl‐2fT and PM6 and PY‐TT are completely different, excellent miscibility is found between BN‐Cl‐2fT and both of the host PM6 and PY‐TT, which can be interpreted by the crowded phenyl groups anchoring along the backbone of BN‐Cl‐2fT, leading to weak self‐aggregation. Glazing incidence wide‐angle X‐ray diffraction (GIWAXS) measurements explicitly confirm the crystallization of PM6 and PY‐TT and amorphous feature of BN‐Cl‐2fT. Furthermore, adding 10 wt% BN‐Cl‐2fT to PM6:PY‐TT can significantly enhance the crystallization of the host polymers. Thus the ternary devices based on PM6:PY‐TT:BN‐Cl‐2fT afford promote short‐circuit current density (JSC, 23.29 vs. 21.80 mA cm−2), fill factor (FF, 62.4% vs. 60.0%), and power conversion efficiency (PCE, 13.70% vs. 12.23%) in contrast to these parameters of binary devices based on PM6:PY‐TT. This work provides a unique and enlightening avenue to design high performance all‐PSCs by adding amorphous B←N embedded polymers as guest component to enhance host‐crystallization. [ABSTRACT FROM AUTHOR]