Tailoring the Molecular Planarity of Perylene Diimide‐Based Third Component toward Efficient Ternary Organic Solar Cells

Abstract Incorporating a third component into binary organic solar cells (b‐OSCs) has provided a potential platform to boost power conversion efficiency (PCEs). However, gaining control over the non‐equilibrium blend morphology via the molecular design of the perylene diimide (PDI)‐based third component toward efficient ternary organic solar cells (t‐OSCs) still remains challenging. Herein, two novel PDI derivatives are developed with tailored molecular planarity, namely ufBTz‐2PDI and fBTz‐2PDI, as the third component for t‐OSCs. Notably, after performing a cyclization reaction, the twisted ufBTz‐2PDI with an amorphous character transferred to the highly planar fBTz‐2PDI followed by a semi‐crystalline character. When incorporating the semi‐crystalline fBTz‐2PDI into the D18:L8‐BO system, the resultant t‐OSC achieved an impressive PCE of 18.56%, surpassing the 17.88% attained in b‐OSCs. In comparison, the addition of amorphous ufBTz‐2PDI into the binary system facilitates additional charge trap sites and results in a deteriorative PCE of 14.37%. Additionally, The third component fBTz‐2PDI possesses a good generality in optimizing the PCEs of several b‐OSCs systems are demonstrated. The results not only provided a novel A‐DA'D‐A motif for further designing efficient third component but also demonstrated the crucial role of modulated crystallinity of the PDI‐based third component in optimizing PCEs of t‐OSCs.