1,4-Dimethoxynaphthalene as a Solid Additive for Improved Photovoltaic Performance in Organic Solar Cells

Morphology optimization of blend films is an essential strategy to enhance the photovoltaic performance of organic solar cells (OSCs). Additive engineering is effective for fine-tuning the active layer morphology. Given the limited efforts and achievements in designing and synthesizing liquid additives, new solid additives to manipulate the morphology of active layers have gained widespread attention. Herein, 1,4-dimethoxynaphthalene (DMNA), with the merits of simple structure, low cost, and ecofriendliness, is successfully incorporated as a novel solid additive to optimize the performance in OSCs based on D18-Cl:N3. The relationship between different DMNA contents and the device performance has been investigated. It is found that the active layer morphology can be effectively regulated by DMNA, leading to an enhanced molecular packing in the blend films, which favors exciton dissociation, charge transfer, and suppression of charge recombination. As a result, 18.61% power conversion efficiency (PCE) has been obtained in the D18-Cl:N3 binary devices incorporated with the solid additive DMNA, better than 17.21% PCE for the binary control device. This is primarily due to the simultaneous increase of the short-circuit current density and fill factor. Furthermore, the general applicability of DMNA as an effective solid additive has been confirmed in other organic photovoltaic systems. These results suggest that DMNA presents potential prospects for regulating bulk heterojunction morphology toward high-performance and high-stability OSCs.