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Noble-metal catalyst is widely-used to synthesize high-efficiency photovoltaic materials. However, expensive catalysts are difficult to remove and the residual catalysts have deleterious effects on photovoltaic performance. In this study, novel efficient non-fullerene acceptors (NFAs) are synthesized via simple nucleophilic substitution without any noble-metal catalyst. An impressive power conversion efficiency (PCE) of 8.91% is obtained using a single triazine-cored NFA, called NAQ-3. To the best of our knowledge, this is the highest PCE for NFAs synthesized via simple nucleophilic substitution or noble-metal-free reactions. Moreover, a delicate four-armed NFA with a bitriazine core, called NAQ-4, is synthesized as an extension example of this synthesis method. Furthermore, the absorption spectra and energy levels of NAQ-3 and NAQ-4 are compared, and the photovoltaic performance, dissociation process and underlying recombination mechanisms of NAQ-3-and NAQ-4-based organic solar cells are analyzed to determine the structure-performance relationship. The results indicate a successful example of high-performance NFAs synthesized via nucleophilic substitution reactions.

sunlight-to-energy harvesting technology. During the last decade, the power conversion efficiency (PCE) soared [1][2][3] because the rapid progress of nonfullerene acceptors (NFAs), [4][5][6][7][8] typically the ring-fused electron acceptors, [9][10][11] and matched donor polymers. [12][13][14] Among different types of NFAs, perylene diimides (PDI)-based NFAs has been extensively investigated because of its good electron transport ability, strong absorption in visible range and robust structure. [15][16][17][18][19] Compared with other wide-bandgap NFAs, PDI has simple structure, and is easy to synthesize, and can modify its own photoelectric properties via simple chemical variation. PDI oligomers with three-dimensional geometry are constructed via functionalization at bay positions (1,6,7,12-positions), [20,21] ortho positions (2,5,8,11-positions) [22,23] or imide positions [24][25][26] to decrease the domain size, thus forming smooth and nano-scale interpenetrating network in the active layer. Then strategies of hetero-atom annulation, [27][28][29] ring-fusion, [30][31][32] intramolecular orientation of PDI moieties [31,33] and molecular lock [34][35][36] have been developed to release the steric hindrance between the core unit and the PDI moiety which would twist the PDI planar unit and is detrimental for intermolecular π−π stacking and thus electron transport ability. [23,37] As a result, the PCE of PDI-based NFAs has exceeded 11%. [35,38] Compared with the prosperity in the development of PDIbased NFAs, the development of matched narrow bandgap donor polymers with appropriated energy levels and complementary absorption spectrum is overlooked although it is equivalently important to boost the PCE value. [35,39,40] All the PDIbased OSCs with PCE value above 10% used P3TEA [31,38] or its derivative PTTEA [34][35][36] as the donor materials. The carboxylate groups in P3TEA could down-shift the energy levels, enhance the crystallinity of the donor polymers and introduce larger and purer domains. [41,42] This design strategy might shed light on modifying the star narrow bandgap donor polymer PTB7-Th. [43] It has been reported that chlorinated on the conjugated The scarcity of narrow bandgap donor polymers matched with perylene diimides (PDI)-based nonfullerene acceptors (NFAs) hinders improvement of the power conversion efficiency (PCE) value of organic solar cells (OSCs).Here, it is reported that a narrow bandgap donor polymer PDX, the chlorinated derivative of the famous polymer donor PTB7-Th, blended with PDI-based NFA boosts the PCE value exceeding 10%. The electroluminescent quantum efficiency of PDX-based OSCs is two orders of magnitude higher than that of PTB7-Th-based OSCs;therefore, the nonradiative energy loss is 0.103 eV lower. This is the highest PCE value for OSCs with the lowest energy loss using the blend of PTB7-Th derivatives and PDI-based NFAs as the active layer. Besides, PDX-based devices showed larger phase separation, faster charge mobilities, higher exciton dissociation probability, suppress...

Single perylene diimide (PDI) used as a non-fullerene acceptor (NFA) in organic solar cells (OSCs) is enticing because of its low cost and excellent stability. To improve the photovoltaic performance, it is vital to narrow the bandgap and regulate the stacking behavior. To address this challenge, we synthesize soluble perylenetetracarboxylic bisbenzimidazole (PTCBI) molecules with a bulky side chain at the bay region, by replacing the widely used “swallow tail” type alkyl chains at the imide position of PDI molecules with a planar benzimidazole structure. Compared with PDI molecules, PTCBI molecules exhibit red-shifted UV–vis absorption spectra with larger extinction coefficient, and one magnitude higher electron mobility. Finally, OSCs based on one soluble PTCBI-type NFA, namely MAS-7, exhibit a champion power conversion efficiency (PCE) of 4.34%, which is significantly higher than that of the corresponding PDI-based OSCs and is the highest PCE of PTCBI-based OSCs reported. These results highlight the potential of soluble PTCBI derivatives as NFAs in OSCs. Graphical abstract