Organic photovoltaic (OPV) devices, which can directly convert absorbed sunlight to electricity, are stacked thin films of tens to hundreds of nanometers. They have emerged as a promising candidate for affordable, clean, and renewable energy. In the past few years, a rapid increase has been seen in the power conversion efficiency of OPV devices toward 10% and above, through comprehensive optimizations via novel photoactive donor and acceptor materials, control of thin-film morphology on the nanoscale, device structure developments, and interfacial and optical engineering. The intrinsic problems of short exciton diffusion length and low carrier mobility in organic semiconductors creates a challenge for OPV designs for achieving optically thick and electrically thin device structures to achieve sufficient light absorption and efficient electron/hole extraction. Recent advances in the field of OPV devices are reviewed, with a focus on the progress in device architecture and optical engineering approaches that lead to improved electrical and optical characteristics in OPV devices. Successful strategies are highlighted for light wave distribution, modulation, and absorption promotion inside the active layer of OPV devices by incorporating periodic nanopatterns/nanostructures or incorporating metallic nanomaterials and nanostructures.

Efficient charge generation is a prerequisite to achieve high power conversion efficiency (PCE) in organic/polymer solar cells (OSCs/PSCs), which involves photoinduced electron transfer and/or hole transfer between the donor/acceptor interface upon photoexcitation. A high yield of charge from both processes usually requires sufficient energy offset between the donor and acceptor for charge separation, fast transport, and extraction for charge collection, as well as significant absorption complementation to maximize photon harvest. Here we demonstrate highly efficient PSCs with efficient dual photocurrent generation pathways from a blend of a polymer donor and two narrow-bandgap nonfullerene acceptors, with an outstanding certified PCE of 13.0% (verified as 12.5%) in PSCs with single-junction device architecture. The devices from these material systems show nonradiative recombination loss of ∼0.22–0.24 V, one of the smallest values for OSCs achieved so far and comparable to those of solar cells based on monocrystalline Si or metal-halide perovskites. This study highlights that dual charge generation pathways with high yield and strongly reduced voltage loss are indispensable for further increasing the PCE of OSCs.

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For a highly efficient tandem organic solar cell, it is important for the subcells to minimize the absorption overlap and generate high and balanced currents. Considering the strong absorption and high external quantum efficiency at the short wavelength, developing a highly efficient blend system with a wide-bandgap (WBG) polymer as the donor and a fullerene derivative as the acceptor in the front cell would be an effective strategy. However, it is a challenge to obtain a high short-current density (J sc ) for this blend system. Here, we develop a WBG polymer (PBD1) with an optical bandgap of 1.88 eV. The PBD1:PC 71 BM blend system with a thickness of 230 nm achieves a power conversion efficiency (PCE) of 9.8% with a high J sc of 14.6 mA cm −2 . When tandem devices are fabricated with PBD1:PC 71 BM in the front cell, a PCE of 14.2% with a high J sc of 12.3 mA cm −2 is achieved.

Wide bandgap polymers based on DTPO were designed for high performance OFETs and PSCs.