摘要： Organic photovoltaics (OPVs) have attracted much attention because of the advantages in low-cost and large-area fabrication and the great potentials in achieving flexible and semi-transparent devices. However, compared with inorganic and perovskite solar cells, OPVs show relatively low photoelectric conversion efficiencies, which is admittedly attributed to intrinsically low dielectric constants of organic materials resulting in large energy losses. With the rapid development of fused-ring electron acceptors especially with an acceptor (A)-donor (D)-acceptor (A) arrangement, PCEs of OPV devices quickly surpassed 12% and even reached 16% in a very short period, in quite a few of which the Elosss are less than 0.6 eV. Although it is common for inorganic or perovskite solar cells, high-performance OPVs with the Elosss less than 0.5 eV are quite rare up to date, which means that the Eloss is still the key factor that limits the photovoltaic efficiency of the OPV technique. Nonetheless, progresses in the development of efficient OPVs by reducing the Eloss to less than 0.5 eV have been made in the past few years.