Branched alkyl-chain engineering of chlorinated asymmetrical acceptors for improved organic photovoltaic performance. Issue 40 (28th September 2022)

• Record Type: Journal Article
• Authors: Li, Dandan; Li, Gang; Li, Zhixiang; Meng, Lingxian; Xu, Yan; Cui, Guanwei; Bai, Yunfei; Wan, Xiangjian; Chen, Yongsheng; Tang, Bo
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 40(2022)
• Page Start: 21633
• Page End: 21641
• Publication Date: 2022-09-28
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2ta05846d
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Six dithieno[3, 2- b :2′, 3′- d ]pyrrole (DTP)-based asymmetric non-fullerene acceptors (NFAs) were designed and synthesized to investigate the effects of DTP linked by gradient alkyl chains on the performance of organic solar cells. Abstract : Side chains generally dictate molecular packing and film morphology and critically affect the efficiency of organic solar cells (OSCs), and hence, side-chain engineering plays a substantial role in achieving high-performance OSCs. In this work, a series of non-fullerene acceptor molecules with A–D–A structures, L6–L11, having gradient branched alkyl-chains on dithieno[3, 2- b :2′, 3′- d ]pyrrole (DTP)-based asymmetrical chlorinated acceptors were designed and synthesized. The effects of branched alkyl-chain length, ranging from n -butyl to 2-decyldodecyl chains, on their optoelectronic properties, thin film molecular packing, blend film morphology and overall photovoltaic performance were systematically studied. Interestingly, the results indicated that with the increase in alkyl-chain length, the open-circuit-voltage ( V OC ) is monotonously increased, while the short-circuit current density ( J SC ), fill factor (FF) and power conversion efficiencies (PCEs) perceive a distinct parabolic trend. The reasons for the variation trend of photoelectric parameters were analyzed. Finally, a 2-butyloctyl chain-containing acceptor L8-based device demonstrated a champion PCE of 15.40% with a V OC of 0.864 V, a J SC of 23.63 mA cm −2 and an FF of 0.754, which is the highest PCE for non-fullerene binary OSCs based on asymmetric ITIC-type acceptors. Further studies indicate that the proper 2-butyloctyl side chain could induce more favorable face-on molecule orientation, enhance carrier mobility, balance charge transport and suppress recombination loss. Our results will provide valuable guidelines for accelerating the understanding of the acceptor structure-photovoltaic performance relationship of OSC materials.