In organic photovoltaics, morphological control of donor and acceptor domains on the nanoscale is key for efficient exciton diffusion and dissociation, carrier transport, and suppression of recombination losses. To realise this, here, we demonstrated a double-fibril network based on ternary donor:acceptor morphology with multi-length scales constructed by combining ancillary conjugated polymer crystallizers and non-fullerene acceptor filament assembly. Using this approach, we achieved an average power conversion efficiency of 19.3% (certified 19.2%). The success lies in the good match between the photoelectric parameters and the morphological characteristic lengths, which utilizes the excitons and free charges efficiently. This strategy leads to enhanced exciton diffusion length (hence exciton dissociation yield) and reduced recombination rate, hence minimizing photon-to-electron losses in the ternary devices as compared to their binary counterparts. The double-fibril network morphology strategy minimizes losses and maximizes the power output, offering the possibility towards 20% power conversion efficiencies in single-junction organic photovoltaics. MainOrganic semiconductors offer the advantage of high optical absorption and tunable energy levels, enabling thin-film solar cells with high light-to-electron conversion efficiencies over a wide range of wavelengths [1][2][3][4] . Desipte recent progresses, the performance of organic solar cells (OSCs) is still limited by non-ideal exciton and charge transport, which depend not only on the electronic structure of organic semiconductors but also on the nanostructure that is formed by material crystallization and phase separation in a bulk heterojunction (BHJ) setting [5][6][7][8] . A suitable sized phase-separated morphology that balances crystalline region and mixing domain on the nanoscale is therefore needed to further push the power conversion efficiency (PCE) of OSCs, however it is a

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Organic semiconductors are emerging as a viable alternative to amorphous silicon in a range of thin‐film transistor devices. With the possibility to formulate these p‐type materials as inks and subsequently print into patterned devices, organic‐based transistors offer significant commercial advantages for manufacture, with initial applications such as low performance displays and simple logic being envisaged. Previous limitations of both air stability and electrical performance are now being overcome with a range of both small molecule and polymer‐based solution‐processable materials, which achieve charge carrier mobilities in excess of 0.5 cm2 V−1 s−1, a benchmark value for amorphous silicon semiconductors. Polymer semiconductors based on thienothiophene copolymers have achieved amongst the highest charge carrier mobilities in solution‐processed transistor devices. In this Progress Report, we evaluate the advances and limitations of this class of polymer in transistor devices.

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resulting in inefficient charge separation and collection. [7][8][9] However, recent progresses show quite steep climbing of power conversion efficiency (PCE) for all-PSCs, reaching a value over 10%, [10][11][12] under systematic optimization, leaving a large gap to be filled in understanding the mechanism of morphology evolution. Polymer blends that reach nanoscaled phase separation in organic photovoltaic (OPV) application have distinctive advantages. They are more suitable for printing fabrication because of their good filmforming ability and mechanical flexibility, prominent device stability, and readily tunable ink viscosity. [13][14][15][16][17] Such benefits make all-PSC unique in scalable OPV fabrication, which also leads to boosted interest in understanding and manipulating the morphology. Initiative efforts on all-PSC printing have been surveyed, showing PCEs way below device made by spin-coating. [16,18] The mystery lies in morphology control, of which BHJ thin film is typical nonequilibrium nature that film-drying kinetics dictates the final nanostructure composed of crystalline networks and mixed and phase-separated domains. [19][20][21] It has been shown that solar cells using polymer:non-fullerene acceptor blends processed by slot die printing have exceed 11% in PCE, [22][23][24][25][26][27][28] from which we think that fine-tuning of morphology in all-PSCs could reach a similar level once a All-polymer solar cells (all-PSCs) exhibit excellent stability and readily tunable ink viscosity, and are therefore especially suitable for printing preparation of large-scale devices. At present, the efficiency of state-of-the-art all-PSCs fabricated by the spin-coating method has exceeded 11%, laying the foundation for the preparation and practical utilization of printed devices.A high power conversion efficiency (PCE) of 11.76% is achieved based on PTzBI-Si:N2200 all-PSCs processing with 2-methyltetrahydrofuran (MTHF, an environmentally friendly solvent) and preparation of active layers by slot die printing, which is the top efficient for all-PSCs. Conversely, the PCE of devices processed by high-boiling point chlorobenzene is less than 2%. Through the study of film formation kinetics, volatile solvents can freeze the morphology in a short time, and a more rigid conformation with strong intermolecular interaction combined with the solubility limit of PTzBI-Si and N2200 in MTHF results in the formation of a fibril network in the bulk heterojunction. The multilength scaled morphology ensures fast transfer of carriers and facilitates exciton separation, which boosts carrier mobility and current density, thus improving the device performance. These results are of great significance for large-scale printing fabrication of high-efficiency all-PSCs in the future. Polymer Solar Cells