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The large energy loss (Eloss) is one of the main obstacles to further improve the photovoltaic performance of organic solar cells (OSCs), which is closely related to the charge transfer (CT) state. Herein, ternary donor alloy strategy is used to precisely tune the energy of CT state (ECT) and thus the Eloss for boosting the efficiency of OSCs. The elevated ECT in the ternary OSCs reduce the energy loss for charge generation (ΔECT), and promote the hybridization between localized excitation state and CT state to reduce the nonradiative energy loss (ΔEnonrad). Together with the optimal morphology, the ternary OSCs afford an impressive power conversion efficiency of 19.22% with a significantly improved open‐circuit voltage (Voc) of 0.910 V without sacrificing short‐cicuit density (Jsc) and fill factor (FF) in comparison to the binary ones. This contribution reveals that precisely tuning the ECT via donor alloy strategy is an efficient way to minimize Eloss and improve the photovoltaic performance of OSCs. [ABSTRACT FROM AUTHOR]

Two new fused‐ring electron acceptor (FREA) isomers with nonlinear and linear molecular conformation, m‐BAIDIC and p‐BAIDIC, are designed and synthesized. Despite the similar light absorption range and energy levels, the two isomers exhibit distinct electron reorganization energies and molecular packing motifs, which are directly related to the molecular conformation. Compared with the nonlinear acceptor, the linear p‐BAIDIC shows more ordered molecular packing and higher crystallinity. Furthermore, p‐BAIDIC‐based devices exhibit reduced nonradiative energy loss and improved charge transport mobilities. It is beneficial to enhance the open‐circuit voltage (VOC) and short‐current current density (JSC) of the devices. Therefore, the linear FREA, p‐BAIDIC yields a relatively higher efficiency of 7.71% in the binary device with PM6, in comparison with the nonlinear m‐BAIDIC. When p‐BAIDIC is incorporated into the binary PM6/BO‐4Cl system to form a ternary system, synergistic enhancements in VOC, JSC, fill factor (FF), and ultimately a high efficiency of 17.6% are achieved. [ABSTRACT FROM AUTHOR]

The donor/acceptor interaction in non‐fullerene organic photovoltaics leads to the mixing domain that dictates the morphology and electronic structure of the blended thin film. Initiative effort is paid to understand how these domain properties affect the device performances on high‐efficiency PM6:Y6 blends. Different fullerenes acceptors are used to manipulate the feature of mixing domain. It is seen that a tight packing in the mixing region is critical, which could effectively enhance the hole transfer and lead to the enlarged and narrow electron density of state (DOS). As a result, short‐circuit current (JSC) and fill factor (FF) are improved. The distribution of DOS and energy levels strongly influences open‐circuit voltage (VOC). The raised filling state of electron Fermi level is seen to be key in determining device VOC. Energy disorder is found to be a key factor to energy loss, which is highly correlated with the intermolecular distance in the mixing region. A 17.53% efficiency is obtained for optimized ternary devices, which is the highest value for similar systems. The current results indicate that a delicate optimization of the mixing domain property is an effective route to improve the VOC, JSC, and FF simultaneously, which provides new guidelines for morphology control toward high‐performance organic solar cells. [ABSTRACT FROM AUTHOR]