Comprehensive Insight into the Structure Contribution of A2‐A1‐D‐A1‐A2 Acceptor to Performance of P3HT Solar Cells

Abstract Poly(3‐hexylthiophene) (P3HT) acting as one of the most popular and low‐cost polymers is quite suitable for commercialization of organic solar cells but suffers from low power conversion efficiency (PCE) because of the limited matching non‐fullerene acceptors (NFAs). One important reason that restricts the enhancement but remains unresolved is the undisclosed contributions of the subtle structure modification to the obvious performance change. In combination with the previous reports and this work, herein A 2 ‐A 1 ‐D‐A 1 ‐A 2 type NFAs with single, dual, and triple modifications based on parent BTA3 is designed, including benzyl‐substitution on A 2 group (namely Bn modification), fluorine‐substitution on A 1 group (namely F modification), and thieno[3,2‐ b ]thiophene‐substitution on D group (namely TT modification). It is finally found that the binary devices of P3HT with these NFAs underwent unexpected variations in the aspect of molecular optoelectronic property, blend morphological feature and charge generation process. The triple modification (including Bn, F, and TT) gives full play to their unique advantages and consequently increases PCE by 60%. To the knowledge, the obtained optimal PCE is one of the highest values for A 2 ‐A 1 ‐D‐A 1 ‐A 2 type NFAs. This study provides clearer insights into the rational substitutions on the A 2 ‐A 1 ‐D‐A 1 ‐A 2 acceptors matched with P3HT for high‐performance organic photovoltaics.