Design and synthesis of solution processable small molecules towards high photovoltaic performance
作者:Zaifang Li、Qingfeng Dong、Yaowen Li、Bin Xu、Meng Deng、Jianing Pei、Jibo Zhang、Feipeng Chen、Shanpeng Wen、Yajun Gao、Wenjing Tian
DOI:10.1039/c0jm02510k
日期:——
We successfully synthesized a series of novel symmetrical solution processable small molecules (APPM, AAPM and ATPM) consisting of the electron-accepting moiety (2-pyran-4-ylidenemalononitrile) (PM) and the electron-donating moiety (triphenylamine) linked by different electron-donating moieties (phenothiazine, triphenylamine and thiophene) through a Suzuki coupling reaction. Differential scanning calorimetry (DSC) measurement indicates that APPM and AAPM shows relatively high glass-transition temperature of ca. 137 °C and 163 °C, while the melting point of ATPM is at ca. 164 °C. UV-vis absorption spectra show that the combination of the PM moiety with moieties with a gradually increased electron-donating ability results in an enhanced intramolecular charge transfer (ICT) transition, which leads to an extension of the absorption spectral range and a reduction of the band gap of the molecules. Both cyclic voltammetry measurement and theoretical calculations displayed that the highest occupied molecular orbital (HOMO) energy levels of the molecules could be fine-tuned by changing the electron-donating ability of the electron-donating moieties. The bulk heterojunction (BHJ) photovoltaic devices with a structure of ITO/PEDOT/PSS/small molecules/PCBM/LiF/Al were fabricated by using the small molecules as donors and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as acceptor. Power conversion efficiencies (PCE) of 0.65%, 0.94% and 1.31% were achieved for the photovoltaic devices based on APPM/PCBM, AAPM/PCBM and ATPM/PCBM under simulated AM 1.5 illumination (100 mW cm−2), respectively. The open circuit voltage of 1.0 V obtained from the device based on ATPM/PCBM is one of the highest values for organic solar cells based on solution processable small molecules.
我们成功合成了一系列新型对称的可溶液处理的小分子(APPM、AAPM 和 ATPM),这些小分子由电子受体部分(2-吡喃-4-亚基丙腈)(PM)和电子供体部分(三苯胺)通过不同的电子供体部分(苯噻嗪、三苯胺和噻吩)通过铃木耦合反应链接而成。差示扫描量热法(DSC)测量表明,APPM 和 AAPM 具有相对较高的玻璃转变温度,分别约为 137 °C 和 163 °C,而 ATPM 的熔点约为 164 °C。紫外-可见吸收光谱表明,PM 部分与具有逐渐增大电子供给能力的部分的组合导致增强的分子内电荷转移(ICT)跃迁,这导致吸收光谱范围的扩展和分子带隙的减少。循环伏安法测量和理论计算显示,通过改变电子供体部分的电子供给能力,可以精细调节分子的最高占有分子轨道(HOMO)能级。利用小分子作为供体,(6,6)-苯基 C61-丁酸甲酯(PCBM)作为受体,构建了结构为 ITO/PEDOT/PSS/小分子/PCBM/LiF/Al 的散装异质结(BHJ)光伏器件。基于 APPM/PCBM、AAPM/PCBM 和 ATPM/PCBM 的光伏器件在模拟 AM 1.5 照明(100 mW cm−2)下分别获得了 0.65%、0.94% 和 1.31%的功率转换效率(PCE)。基于 ATPM/PCBM 的器件获得的开路电压 1.0 V 是基于可溶液处理小分子的有机太阳能电池中最高的值之一。