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

All-small-molecule organic solar cells (SM-OSCs) with a high power conversion efficiency (PCE) of 15.88% (certified 15.5%) are demonstrated by employing 4TIC as the additional non-fullerene acceptor (NFA) to construct ternary SM-OSCs. 4TIC is a highly crystalline acceptor with a similar molecular structure as 6TIC, the host NFA in the binary blend. The addition of 4TIC not only significantly enhances the crystallinity of the blend film but also maintains the desired face-on orientation in the proper multi-length scale morphology to improve both charge extraction and recombination in devices. As a result, the PCE of the ZnP-TBO: 6TIC-based SM-OSCs increases from 12.11% to 14.73% after the addition of 4TIC. For ZnP-TSEH: 6TIC-based SM-OSCs, the PCE increases from 13.54% to 15.88% (certified 15.5%) after the addition of 4TIC. The 15.88% efficiency is the best result for SM-OSCs reported to date.