A Low‐Cost 3D Spirobifluorene‐Based Acceptor for High‐Performance Ternary Organic Solar Cells

Abstract The advantages of 3D materials as guest components of ternary organic solar cells (TOSCs) are being realized, showing great potential in improving device performance. However, the correlation between their distinctive 3D structure and device performance remains largely unexplored. Herein, a 3D acceptor named SF‐HR is cost‐effectively synthesized utilizing a twisted spirofluorene core. SF‐HR shows an edge‐on oriented packing but not the disordered aggregation as other 3D molecules. When introduced into D18:Y6 binary system, SF‐HR can induce more predominant face‐on packing and finer domain size in ternary blend, which facilitates exciton dissociation and multi‐direction charge transport. Besides, SF‐HR exhibits complementary absorption and cascaded energy levels with D18 and Y6, contributing to the improvement of short‐circuit current density ( J sc ) and open‐circuit voltage ( V oc ), respectively. Accordingly, the optimized ternary device achieves higher V oc of 0.893 V, J sc of 27.13 mA cm −2 , and fill factor (FF) of 77.8%, respectively, than that of the host binary device, yielding an excellent efficiency of 18.85%. This success demonstrates that the utilization of a crystalline 3D material as a guest component represents a promising strategy for achieving state‐of‐the‐art OSCs, which is conducive to understanding the relationship between 3D guest structure and device performance from a new perspective.