烷硫噻吩基苯并二噻吩基聚合物的合成与光电性能

Synthesis and Photoelectric Properties of Alkylthio Side Chains Substituted Benzodithiophenyl Polymer

通过在[1,2-b∶4,5-b′]苯并二噻吩(BDT)的侧链引入硫原子,并与氟代的苯并三氮唑偶联合成共轭聚合物PBDT-AST-FBTA.将其和侧链为烷基噻吩的共轭聚合物PBDT-OT-FBTA进行了聚集性能、介电常数及光电性能的表征.两种共轭聚合物在350~630 nm之间有较强的吸光能力,其光学带隙分别是1.94 eV和1.96 eV,最高占据分子轨道(HOMO)能级分别是-5.36 eV和-5.22 eV.硫原子的引入相对介电常数从3.6增加至4.2,并提高了共轭聚合物的聚集性能.将PBDT-AST-FBTA和PBDT-OT-FBTA与非富勒受体小分子ITIC制备有机聚合物太阳能电池(OPVs)器件,研究结果表明,在共轭聚合物侧链引入硫原子,制备的光伏器件的开路电压(V OC)有了明显的提高,从而使其能量转换效率(PCE)提高了11.5%.

Two D-A copolymers named PBDT-OT-FBTA and PBDT-AST-FBTA,which were derived from 4,5-dicotylthiophen-2-yl(OT)or 4-octyl-4-octylthio-thiophen-2-yl(AST)flanked benzo[1,2-b∶4,5-b′]dithiophene and 4,7-bis(thiophen-2-yl)-5,6-difluoro-2-(2-hexyl-decanyl)-2H-benzotriazole were synthesized via Palladium-catalyzed Stille coupling reaction.The molecular weight,absorption,aggregation and dielectric constant etc.of the copolymers were characterized.The copolyemers exhibit extensive light absorption from 350 nm to 630 nm with the optical band gap of 1.85 and 1.89 eV and the HOMO energy level of-5.36 eV and-5.22 eV.Besides that,it has been found that the dielectric constant of the copolymers were increased from 3.6 to 4.2,at the same time,the aggregation were enhanced while the OT flanks were replaced with the AST flanks.Organic polymer solar cells(OPVs)were fabricated with PBDT-AST-FBTA and PBDT-OT-FBTA and a small non-fuller receptor molecule of ITIC.The results indicated that the replacement of the alkyl side chains with the alkylthio side chains would contribute a lot to the deepening of the HOMO energy levels,and the increasing of the aggregation,dielectric constant of the conjugated polymers,thus lead to the enhancing of the performance of the OPVs from the copolymer.