Designing dithieno-benzodithiophene-based small molecule donors for thickness-tolerant and large-scale polymer solar cells

The power conversion efficiency (PCE) of polymer solar cells (PSCs) has steadily improved; however there remain some unresolved issues. One problem is that the active layer is highly sensitive to its film thickness, limiting the optimal thickness to around 100 nm, which is not suitable for scale-up solar module manufacturing. To address this issue, a method to introduce the designed small molecule donor (SMD) SD62 into host PSCs was implemented. The resulting ternary system exhibits superior charge mobility, reduced charge recombination, and higher fill factor and PCE values, especially for thick-film PM6:L8-BO devices. The PCE of PM6:SD62:L8-BO devices exceeds 17.0% in the 100-400 nm thickness range. The advantage of high efficiency with thickness insensitivity further facilitates large-scale production, confirmed by the manufacturing of large-scale modules. Under similar film thickness distribution, the ternary system with an effective area of 15.4 cm² has higher fill factor (FF) and PCE values (71.59% and 15.94%, respectively) than the binary system (FF = 65.86% and PCE = 13.21%, respectively). Furthermore, this SD62-doping strategy also shows great universality, which is confirmed in three other binary systems, including PM6:Y6, PM6:BTP-eC9, and D18:L8-BO. This work provides a promising SMD-doping strategy for the commercial application of PSCs. © 2024 The Royal Society of Chemistry.