Synthesis and photovoltaic properties of thiophene–imide-fused thiophene alternating copolymers with different alkyl side chains
作者:Tomokazu Umeyama、Masaaki Oodoi、Osamu Yoshikawa、Takashi Sagawa、Susumu Yoshikawa、Douvogianni Evgenia、Noriyasu Tezuka、Yoshihiro Matano、Kati Stranius、Nikolai V. Tkachencko、Helge Lemmetyinen、Hiroshi Imahori
DOI:10.1039/c1jm11531f
日期:——
A series of novel polythiophene derivatives comprised of alternating structures of N-alkylated thieno[3,4-c]pyrrole-4,6-dione (nTPD, n = number of carbon atoms from 11 to 18 in alkyl chains) and pristine thiophene were synthesized by Stille coupling reaction between 2,5-dibromo- or 2,5-diiodo-nTPD and 2,5-bis(tributylstannyl)thiophene. The effect of alkyl side-chain structures at the N-atom of TPD on the optical, electrochemical, and photovoltaic properties has been investigated systematically. In addition, these properties were compared with a widely used polythiophene derivative, i.e., poly(3-hexylthiophene) (P3HT). Optical bandgaps of the obtained polymers PnTPDTs estimated from absorption and fluorescence spectra were 1.8â2.1 eV, which were comparable or smaller than that of P3HT (2.0 eV). HOMO and LUMO energy levels of PnTPDTs were determined by electrochemical and optical measurements. The HOMO levels are â5.4 to â5.7 eV, which are lower than that of P3HT (â5.2 eV). The photovoltaic properties of the devices consisting of PnTPDT (n = 11, 12, 13, 18) with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were investigated. The short-circuit currents (JSC) in the PnTPDT:PCBM devices were relatively low and varied significantly with alkyl side-chain structures (0.81â2.29 mA cmâ2), whereas the open-circuit voltage (VOC) values were higher by 0.1â0.2 V than that in the P3HT:PCBM device. The P12TPDT:PCBM device exhibited the photocurrent generation exceeding wavelength of 750 nm, but the power conversion efficiency was found to be moderate (0.75%).
一系列新颖的聚噻吩衍生物,由N-烷基化的噻吩并[3,4-c]吡咯-4,6-二酮(nTPD,其中n代表烷基链中的碳原子数,范围从11到18)和原始噻吩的交替结构组成,通过Stille偶联反应合成了2,5-二溴或2,5-二碘的nTPD与2,5-双(三丁基锡)噻吩的反应。系统研究了TPD的N原子上烷基侧链结构对光学、电化学和光伏性能的影响。此外,这些性能与广泛使用的聚噻吩衍生物,即聚(3-己基噻吩)(P3HT)进行了比较。从吸收和荧光光谱估计得到的聚合物PnTPDTs的光学带隙为1.8至2.1 eV,与P3HT(2.0 eV)相当或更小。通过电化学和光学测量确定了PnTPDTs的HOMO和LUMO能级。HOMO能级为-5.4至-5.7 eV,低于P3HT(-5.2 eV)。研究了由PnTPDT(n=11, 12, 13, 18)与[6,6]-苯基-C61-丁酸甲酯(PCBM)组成的器件的光伏性能。PnTPDT:PCBM器件中的短路电流(JSC)相对较低,并且随烷基侧链结构的显著变化(0.81至2.29 mA cm-2),而开路电压(VOC)值比P3HT:PCBM器件高0.1至0.2 V。P12TPDT:PCBM器件表现出超过750 nm波长的光电流生成,但功率转换效率中等(0.75%)。