Vertical Stratification Engineering of Insulating Poly(aryl ether)s Enables 18.6% Organic Solar Cells with Improved Stability

Control of the preferred vertical phase distribution of the components in the photoactive layer is of vital importance to improve the device performance and stability of organic photovoltaics (OPVs). Herein, a universal sequential-deposition strategy is demonstrated to realize optimal vertical phase distribution by employing orthogonal solvents and synergistically integrating ternary/quaternary compositions consisting of insulating heat-resistant poly(aryl ether)s as the third/fourth component in a photoactive layer. The selective segregation of poly(aryl ether)s in the middle of the active layer enhances molecular packing of the photovoltaic materials and improves the charge transport and extraction properties. A maximum efficiency of 18.6% is achieved for PM6:BTP-eC9:PC71BM:poly(aryl ether)-based quaternary solar cells, with photo/thermal stability that is better than that of devices without poly(aryl ether). This work provides an effective approach for achieving stable and efficient OPVs with expected topology by tuning molecular packing behaviors and the vertical segregation of multicomponents in photovoltaic layers.