Ternary architecture is a promising strategy to further boost the performance of organic solar cells (OSCs). Reducing the bandgap of the active layer materials not only widens the absorption wavelength range and enhances the short‐circuit current (Jsc) of the OSC, but also decreases the open‐circuit voltage (Voc) of the device, leading to a trade‐off situation for the optimization of the material system. Herein, a small‐molecule donor BTID‐2F, featuring a narrower bandgap than that of PM6, is introduced into a PM6:Y6 based system. The redshift in external quantum efficiency indicates the narrower bandgap and better aggregation in the ternary blends than those of binary ones. Interestingly, lower energy disorder and energy loss are also attained for the ternary devices, leading to higher Voc. Furthermore, owing to the suppressed recombination and morphological optimization, a simultaneous enhancement in the Jsc and fill factor boosts the power conversion efficiency (PCE) of ternary OSC to 17.9% compared to 16.62% for the binary device. Likewise, replacing the acceptor with the L8‐BO molecule further improves the ternary PCE to 18.52%. This work indicates an emerging approach for fabricating high‐performance ternary OSCs with a decreased bandgap and increased Voc.

In organic solar cells (OSCs), the lower dielectric constant of organic semiconductor material induces a strong Coulomb attraction between electron–hole pairs, which leads to a low exciton separation efficiency, especially the charge transfer (CT) state. The CT state formed at the electron‐donor (D) and electron‐acceptor (A) interface is regarded as an unfavorable property of organic photovoltaic devices. Since the OSC works in a nonzero temperature condition, the entropy effect would be one of the main reasons to overcome the Coulomb energy barrier and must be taken into account. In this review, the present understanding of the entropy‐driven charge separation is reviewed and how factors such as the dimensionality of the organic semiconductor, energy disorder effect, the morphology of the active layer, are described, as well as how the nonequilibrium effect affects the entropy contribution in compensating the Coulomb dissociation barrier for CT exciton separation and charge generation process. The investigation of the entropy effect on exciton dissociation mechanism from both theoretical and experimental aspects is focused on, which provides pathways for understanding the underlying mechanisms of exciton separation and further enhancing the efficiency of OSCs.

The excitons are generally decomposed into free charges by the heterojunction due to the low dielectric constant of organic materials. Recent research indicates that owing to the low exciton binding energy, the pure Y6 film can directly and spontaneously generate free charge carriers after photoexcitation, even without the assistance of the donor/acceptor interface driving force. However, the serious bimolecular recombination and trap‐assisted recombination also limit the photovoltaic efficiency of single‐component Y6 devices. Herein, efficient exciton separation and charge collection by changing the buffer layer and using mixed solvents to control the active layer morphology of single‐component devices based on Y6 are achieved. It is found that the short‐circuit current is significantly increased by properly adjusting the proportion of face‐on and edge‐on direction of molecules. Eventually, the power conversion efficiency (PCE) of single‐component devices based on Y6 is increased from 0.15% to 1.41%. The corresponding dynamic process is revealed by ultrafast transient absorption spectroscopy and entropy effect on the exciton dissociation. Effective charge separation and collection in single‐component devices is not only critical to improving the PCE, but provides an in‐depth understanding for the further design of high‐performance multicomponent devices.

Effectively reducing the voltage loss in organic solar cells (OSCs) is critical to improving the power conversion efficiency (PCE) of organic solar cells. In this study, highly efficient ternary OSCs...