The adequate donor/acceptor interface and bicontinuous interpenetrating networks in the BHJ blend facilitates efficient exciton dissociation and charge transport for collection at the electrodes. [5][6][7] In this regard, uniformly phase-separated nanomorphology at the 10-20 nm length scale which formed by the spontaneous phase separation of the donor and acceptor materials has a profound impact on the performance of OSCs. The BHJ bicontinuous interpenetrating network in active layer is formed by the respective self-aggregation of donor and acceptor materials during the film formation process. Nevertheless, due to the different solubility and miscibility of donor and acceptor in processing solvent, casting BHJ blend from a single solvent generally results in an undesirable morphology for efficient OSCs. Therefore, developing morphology control methods to manipulate the morphology of blend film toward advantageous phase separation is critical for fabricating state-of-the-art OSCs. [8][9][10] Incorporation of appropriate solvent as an additive in primary host solvent is one of the most effective and simple approaches to control the aggregation of donor/acceptor materials during the film formation. [11][12][13] The critical operating principles of the solvent additives on controlling the morphology are the selective solubility of solvent additive to either donor or acceptor material and the less volatile with higher boiling points than host solvents. During the past decades in the studies of the OSCs with fullerene derivatives as the dominant acceptors, various kinds of solvents have been developed as additives to optimize the morphology of the fullerene-based blend film because of the characteristic discrepancies between the fullerene derivative acceptors and the π-conjugated p-type organic semiconductor donors. [12] Currently, nonfullerene n-type organic semiconductors with acceptor-donor-acceptor (A-D-A) [14][15][16] or A-DA′D-A [17] molecular backbones have replaced fullerene acceptors as emerging acceptors that significantly drive the development of highly efficient OSCs. Unlike the isotropic cage-like structure of fullerene derivatives, the anisotropic conjugated structures of the nonfullerene acceptors, which are similar to p-type organic semiconductors, bring more complexity and challenge on manipulating their Controlling the self-assembling of organic semiconductors to form welldeveloped nanoscale phase separation in the bulk-heterojunction active layer is critical yet challenging for building high-performance organic solar cells (OSCs). Particularly, the similar anisotropic conjugated structures between nonfullerene acceptors and p-type organic semiconductor donors raise more complexity on manipulating their aggregation toward appropriate phase separation. Herein, a new approach to tune the morphology of photoactive layer is developed by utilizing the synergistic effect of dithieno[3,2-b:2′,3′-d]thiophene (DTT) and 1-chloronaphthalene (CN). The volatilizable solid additive DTT with high crystallinity can r...

Currently, morphology optimization methods for the fused‐ring nonfullerene acceptor‐based polymer solar cells (PSCs) empirically follow the treatments originally developed in fullerene‐based systems, being unable to meet the diverse molecular structures and strong crystallinity of the nonfullerene acceptors. Herein, a new and universal morphology controlling method is developed by applying volatilizable anthracene as solid additive. The strong crystallinity of anthracene offers the possibility to restrict the over aggregation of fused‐ring nonfullerene acceptor in the process of film formation. During the kinetic process of anthracene removal in the blend under thermal annealing, donor can imbed into the remaining space of anthracene in the acceptor matrix to form well‐developed nanoscale phase separation with bi‐continuous interpenetrating networks. Consequently, the treatment of anthracene additive enables the power conversion efficiency (PCE) of PM6:Y6‐based devices to 17.02%, which is a significant improvement with regard to the PCE of 15.60% for the reference device using conventional treatments. Moreover, this morphology controlling method exhibits general application in various active layer systems to achieve better photovoltaic performance. Particularly, a remarkable PCE of 17.51% is achieved in the ternary PTQ10:Y6:PC71BM‐based PSCs processed by anthracene additive. The morphology optimization strategy established in this work can offer unprecedented opportunities to build state‐of‐the‐art PSCs.

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Combining the acceptor–donor–acceptor-type fused ring-based molecular architecture into a polymeric backbone is a promising strategy to design polymer acceptors for high-performance all-polymer solar cells (all-PSCs), and use of single isomer monomers is critical to control their physicochemical and photovoltaic properties. Here, two polymer acceptors (namely, PBI-α and PBI-β) based on two different building blocks are designed and synthesized for investigating the effect of regioisomerism of the building blocks on the physicochemical and photovoltaic properties of the polymer acceptors. The subtle difference in the thienyl-fused malononitrile group of PBI-α and PBI-β significantly influences their absorption spectra and electronic energy levels. PBI-α exhibited a lower lowest unoccupied molecular orbital level and obviously redshifted absorption spectrum compared to PBI-β, which delivered a significantly different open-circuit voltage (0.930 ± 0.004 vs 1.02 ± 0.01 V) and short-circuit current density (18.7 ± 0.3 vs 16.1 ± 0.4 mA cm–2) in the PBI-α- and PBI-β-based devices, respectively. Meanwhile, PBI-β shows a more positive molecular packing effect to enhance the π-face-on orientation backbone stacking of polymer donor PM6 than PBI-α, which is beneficial for efficient charge transport, leading to a higher fill factor of 0.684 in the PBI-β-based all-PSC compared to 0.646 for the PBI-α-based device.

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