Wu Xiaofu, Wang Weijie, Hang Hao, Li Hua, Chen Yonghong, Xu Qian, Tong Hui, Wang Lixiang
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry , Chinese Academy of Sciences , Changchun 130022 , P. R. China.
University of Science and Technology of China , Hefei 230026 , PR China.
ACS Appl Mater Interfaces. 2019 Aug 7;11(31):28115-28124. doi: 10.1021/acsami.9b08017. Epub 2019 Jul 24.
Classical fused-ring electron acceptors (FREAs) with a linear acceptor-donor-acceptor (A-D-A) architecture continuously break records of power conversion efficiency (PCE) in nonfullerene organic solar cells. In contrast, the development of star-shaped FREAs still lags behind. Herein, a new -symmetric and electron-rich core, benzotri(cyclopentadithiophene) (BTCDT) in which the central benzo[1,2-:3,4-':5,6-″]trithiophene fused with three outer thiophenes via three cyclopentadienyl rings, is synthesized and used for the construction of star-shaped FREAs (BTCDT-IC and BTCDT-ICF). Owing to the strong electron-donating ability of the BTCDT unit, both acceptors exhibit the effective intramolecular charge transfer, leading to the strong absorption in the region of 500-800 nm with narrow band gaps below 1.70 eV as well as suitable highest occupied molecular orbital and lowest unoccupied molecular orbital levels. Compared with nonfluorinated BTCDT-IC, fluorinated BTCDT-ICF red-shifts the absorption peak to 688 nm and reduces the band gap to 1.62 eV, which induces a broader external quantum efficiency (EQE) response ranging from 300 to 800 nm and a higher maximum EQE of 70% while blending with a wide band gap polymer donor J61. The J61:the BTCDT-ICF blend film exhibits more suitable phase morphology compared with the J61:BTCDT-IC blend film, which is responsible for the enhanced EQE value, increased short-circuit current density (), and fill factor (FF) in organic solar cell devices. As a result, the J61:BTCDT-ICF-based device yields a best PCE of 8.11% with a high of 16.93 mA cm and a high FF of 65.6%, demonstrating that the BTCDT-based star-shaped FREAs hold great potential for nonfullerene organic solar cells.
具有线性受体-供体-受体(A-D-A)结构的经典稠环电子受体(FREAs)不断打破非富勒烯有机太阳能电池的功率转换效率(PCE)记录。相比之下,星形FREAs的发展仍然滞后。在此,合成了一种新的对称且富电子的核心——苯并三(环戊二噻吩)(BTCDT),其中中心苯并[1,2-:3,4-':5,6-″]三噻吩通过三个环戊二烯基环与三个外部噻吩稠合,并用于构建星形FREAs(BTCDT-IC和BTCDT-ICF)。由于BTCDT单元具有强给电子能力,两种受体均表现出有效的分子内电荷转移,导致在500 - 800 nm区域有强吸收,带隙窄于1.70 eV,以及合适的最高占据分子轨道和最低未占据分子轨道能级。与非氟化的BTCDT-IC相比,氟化的BTCDT-ICF将吸收峰红移至688 nm,并将带隙降低至1.62 eV,这在与宽带隙聚合物供体J61共混时诱导了300至800 nm范围内更宽的外量子效率(EQE)响应以及70%的更高最大EQE。与J61:BTCDT-IC共混膜相比,J61:BTCDT-ICF共混膜表现出更合适的相形态,这导致有机太阳能电池器件中的EQE值提高、短路电流密度()增加和填充因子(FF)提高。结果,基于J61:BTCDT-ICF的器件产生了8.11%的最佳PCE,具有16.93 mA cm的高和65.6%的高FF,表明基于BTCDT的星形FREAs在非富勒烯有机太阳能电池中具有巨大潜力。