Approaching 16% Efficiency in All-Small-Molecule Organic Solar Cells Based on Ternary Strategy with a Highly Crystalline Acceptor

Organic solar cells (OSCs) with great potential for producing light-weight, low-cost, flexible solar cells have attracted much attention in the past few years. Compared with polymer-based OSCs (P-OSCs), small-molecule organic solar cells (SM-OSCs) have unique advantages in commercialization, including well-defined molecular structures and low batch-to-batch variations, despite their power conversion efficiencies (PCEs) being lower. Here, we demonstrate ternary small-molecule organic solar cells (SM-OSCs) with a record-high PCE up to 15.88% (certified 15.5%) by adding 4TIC as the additional acceptor into porphyrin:6TIC blends. The highly crystalline 4TIC significantly enhances the crystallinity of the blend film and maintains the desired face-on orientations and proper multi-length scale morphology, which notably optimizes the charge extraction/recombination in the ternary devices. The ternary devices show a remarkably enhanced short-circuit current density and fill factor, resulting in over 20% enhancement of PCE.