The ternary all-small-molecule organic solar cells deliver a top-ranked power conversion efficiency of 16.28%, benefiting from the rational compatibility in the B1:BO-4Cl:Y7 matrix.

Despite dihalogenation of terminals is an effective strategy to achieve efficient nonfullerene acceptors (NFAs)-based organic solar cells (OSCs), hetero-dihalogenated terminals are quite difficult to obtain. Here, we firstly synthesized two...

Side‐chain tailoring is a promising method to optimize the performance of organic solar cells (OSCs). However, asymmetric alkyl chain‐based small molecular acceptors (SMAs) are still difficult to afford. Herein, we adopted a novel asymmetric n‐nonyl/undecyl substitution strategy and synthesized two A‐D1A′D2‐A double asymmetric isomeric SMAs with asymmetric selenophene‐based central core for OSCs. Crystallographic analysis indicates that AYT9Se11‐Cl forms a more compact and order intermolecular packing compared to AYT11Se9‐Cl, which contributed to higher electron mobility in neat AYT9Se11‐Cl film. Moreover, the PM6 : AYT9Se11‐Cl blend film shows a better morphology with appropriate phase separation and distinct face‐on orientation than PM6 : AYT11Se9‐Cl. The OSCs with PM6 : AYT9Se11‐Cl obtain a superior PCE of 18.12 % compared to PM6 : AYT11Se9‐Cl (17.52 %), which is the best efficiency for the selenium‐incorporated SMAs in binary BHJ OSCs. Our findings elucidate that the promising double asymmetric strategy with isomeric alkyl chains precisely modulates the crystal packing and enhances the photovoltaic efficiency of selenophene‐incorporated SMAs.

Efficient ternary blend organic photovoltaic devices (OPVs) are built based on a D18‐Cl:Y6 host system and star polymer donor PM6 as the third component. A power conversion efficiency (PCE) of 16.89% is achieved in D18‐Cl:Y6 host binary OPVs, with a short‐circuit current density (J SC) of 25.31 mA cm−2, an open‐circuit voltage (V OC) of 0.878 V, and a fill factor (FF) of 75.81%. Upon incorporating appropriate PM6 in active layers, the PCE of optimal ternary blend OPVs can be increased to 17.61%, benefiting from a J SC of 26.35 mA cm−2, a V OC of 0.871 V, and an FF of 76.82%. Polymers D18‐Cl and PM6 have good compatibility and similar highest occupied molecular orbital (HOMO) levels, which enable to form D18‐Cl:PM6 alloyed states for efficient hole transport in ternary blend active layers. Meanwhile, trap density in ternary blend active layers is decreased by incorporating PM6, which is conducive to weaken charge recombination in ternary blend active layers. The gradually varied V OC values of ternary blend OPVs can be well explained from the varied HOMO levels of D18‐Cl:PM6 alloyed states. The results indicate that two compatible polymer donors with similar HOMO levels have great potential in achieving efficient ternary blend OPVs.