Additive-Induced Vertical Component Distribution Enables High-Performance Sequentially Cast Organic Solar Cells

Modulation of the active layer morphology to form a vertical component distribution structure is an effective way of improving the efficiency of organic solar cells (OSCs). In this paper, a layer-by-layer (LbL) spin-coating method was adopted combined with an additive strategy to achieve the purpose of precisely adjusting the morphology, and finally, high-performance OSCs based on a D18-Cl/Y6 system were achieved. After adding n-octane in D18-Cl, D18-Cl+/Y6 devices realized a PCE of 17.70%, while with the incorporation of 1-fluoronaphthalene (FN) in Y6, D18-Cl/Y6+ devices obtained a power conversion efficiency (PCE) of 17.39%, both higher than the control devices (16.66%). The former resulted in a more orderly arrangement of D18-Cl, forming a suitable phase separation morphology, and the latter improved the crystallization of Y6, which facilitated carrier transport. Furthermore, the dual-additive-treated D18-Cl+/Y6+ bilayer devices with n-octane doping in the donor and FN in the acceptor had a more desirable vertical morphology, exhibiting an excellent PCE of 18.16% with an improved JSC of 27.17 mA cm-2 and FF of 76.88%, one of the highest efficiencies for LbL OSCs. The results demonstrated that combining the LbL spin-coating method with the additive strategy is a valid way to achieve hierarchical morphology control and enhance device performance, which is of great significance for the fabrication and development of OSCs.

Automated summary

Modulating the morphology of the active layer using a layer-by-layer spin-coating method combined with an additive strategy is an effective approach to improve the efficiency of organic solar cells. The study successfully achieved high-performance OSCs based on a D18-Cl/Y6 system by precisely adjusting the morphology using this method.