Dithienopyrrole-based donor–acceptor copolymers: low band-gap materials for charge transport, photovoltaics and electrochromism
作者:Xuan Zhang、Timothy T. Steckler、Raghunath R. Dasari、Shino Ohira、William J. Potscavage、Shree Prakash Tiwari、Séverine Coppée、Stefan Ellinger、Stephen Barlow、Jean-Luc Brédas、Bernard Kippelen、John R. Reynolds、Seth R. Marder
DOI:10.1039/b915940a
日期:——
A series of highly soluble donorâacceptor (DâA) copolymers containing N-(3,4,5-tri-n-decyloxyphenyl)-dithieno[3,2-b:2â²,3â²-d]pyrrole (DTP) or N-(2-decyltetradecyl)-dithieno[3,2-b:2â²,3â²-d]pyrrole (DTPâ²) as donor and three different acceptors, 4,7-dithien-2-yl-[2,1,3]-benzothiadiazole, 4,9-dithien-2-yl-6,7-di-n-hexyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline and 4,8-dithien-2-yl-2λ4δ2-benzo[1,2-c;4,5-câ²]bis[1,2,5]thiadiazole (BThX, X = BTD, TQHx2, BBT, respectively) were synthesized by Stille coupling polymerizations. The optical and electrochemical properties of these copolymers were investigated, along with their use in field-effect transistors and photovoltaic devices. The band gaps (eV) estimated from UV-vis-NIR spectra and electrochemical measurements of the copolymers varied from ca. 1.5â0.5 eV, and were consistent with quantum-chemical estimates extrapolated using density functional theory. Oxidative and reductive spectroelectrochemistry of the copolymers indicated they can be both p-doped and n-doped, and three to four differently colored redox states of the polymers can be accessed through electrochemical oxidation or reduction. The DTP-BThBTD and DTP-BThTQHx2 copolymers exhibited average field-effect hole mobilities of 1.2 à 10â4 and 2.2 à 10â3 cm2/(Vs), respectively. DTP-BThBBT exhibited ambipolar field-effect characteristics and showed hole and electron mobilities of 1.2 à 10â3 and 5.8 à 10â4 cm2/(Vs), respectively. Bulk heterojunction photovoltaic devices made from blends of the copolymers with 3â²-phenyl-3â²H-cyclopropa[1,9](C60-Ih)[5,6]fullerene-3â²-butanoic acid methyl ester (PCBM) (1:3 weight ratio) exhibited average power conversion efficiencies as high as 1.3% under simulated irradiance of 75 mW/cm2.
一系列高度可溶的供体-受体(D-A)共聚物,包含N-(3,4,5-三-n-十三烷氧基苯基)-二噻吩并[3,2-b:2',3'-d]吡咯(DTP)或N-(2-癸基十四烷基)-二噻吩并[3,2-b:2',3'-d]吡咯(DTP')作为供体,三种不同受体,4,7-二噻吩-2-基-[2,1,3]-苯并噻二唑,4,9-二噻吩-2-基-6,7-二-n-己基-[1,2,5]噻二唑并[3,4-g]喹喔啉和4,8-二噻吩-2-基-2Λ4Δ2-苯并[1,2-c;4,5-c']双[1,2,5]噻二唑(BThX,X分别为BTD、TQHx2、BBT)通过Stille偶联聚合合成。研究了这些共聚物的光学和电化学性质,以及它们在场效应晶体管和光伏器件中的应用。从UV-vis-NIR光谱和电化学测量估算的带隙(eV)在约1.5至0.5 eV之间变化,并与使用密度泛函理论外推的量子化学估算一致。共聚物的氧化和还原光谱电化学表明它们可以进行p型和n型掺杂,通过电化学氧化或还原可以得到三到四种不同颜色的氧化还原状态。DTP-BThBTD和DTP-BThTQHx2共聚物表现出平均场效应空穴迁移率分别为1.2 × 10^-4和2.2 × 10^-3 cm2/(Vs)。DTP-BThBBT表现出双向场效应特性,空穴和电子迁移率分别为1.2 × 10^-3和5.8 × 10^-4 cm2/(Vs)。由这些共聚物与3'-苯基-3'H-环丙并[1,9](C60-Ih)[5,6]富勒烯-3'-丁酸甲酯(PCBM)(重量比1:3)混合制成的体异质结光伏器件在模拟辐照度75 mW/cm2下表现出高达1.3%的平均功率转换效率。