Layer-by-layer processing enabled alloy-like ternary organic solar cells to achieve 17.9% efficiency.

The vertical composition distribution and crystallinity of the active layer are considered to have critical roles in the performance enhancement of organic solar cells (OSCs). In this paper, a layer-by-layer (LbL) spin-coating method is combined with a ternary strategy to achieve effective OSCs based on the PM6/N3 system. Compared with BHJ OSCs, LbL OSCs achieve ideal morphology tuning with an increase in the highest power conversion efficiency (PCE) from 15.72% to 16.94%. In addition, the polymer PTO2, which has the same structural unit as the donor PM6, is introduced into the active layer to form a donor alloy, facilitating charge transfer and enhancing the stability of devices. Ultimately, the ternary LbL OSCs have vertically distributed structures which inhibit bimolecular recombination, obtaining an optimum PCE of 17.90%, an open circuit voltage (V_OC) of 0.860 V, a short circuit current density (J_SC) of 27.57 mA cm⁻² and a fill factor (FF) of 75.98%. The results show that the ternary alloy model combined with the LbL spin-coating method is an effective way to overcome the difficulties in morphology regulation and achieve high-performance OSCs. [ABSTRACT FROM AUTHOR]