氟对含噻并[3,2-b]噻吩π桥的苯并三氮唑基共聚物的光伏性能影响

Effect of Fluorine on the Photovoltaic Property of Benzotriazole-Based Copolymers Containing Thieno[3,2-b]thiophene π Bridge

以噻并[3,2-b]噻吩(TT)修饰的二维苯并[1,2-b:4,5-b′]二噻吩(BDT)作给电子单元、TT作共轭π桥、苯并[d][1,2,3]三氮唑(BTA)或5,6-二氟苯并[d][1,2,3]三氮唑(FBTA)作缺电子单元,在三(二亚苄基丙酮)二钯(Pd2(dba)3)、三(邻甲苯基)膦(P(o-tol)3)催化剂体系下通过Stille缩合聚合方法制备了宽带隙共聚物PTTBDT-BTA和PTTBDT-FBTA。用核磁共振氢谱(~1 H-NMR)和碳谱(^(13)C-NMR)、元素分析、凝胶渗透色谱(GPC)、热重分析、紫外-可见吸收光谱和循环伏安法等对其进行了表征。系统研究了氟取代对材料的热稳定性、成膜性、吸收光谱、溶液状态下的聚集行为、固态薄膜的光稳定性、能级和光伏性能的影响。研究表明:相比PTTBDT-BTA,氟代聚合物PTTBDT-FBTA失重5%的热分解温度提高了20℃、溶解性明显变差、薄膜态吸光范围稍微变窄、氯苯溶液状态下聚合物链间聚集作用显著增强、薄膜的光稳定性提高且最高分子占有轨道能级(EHOMO)下降了0.10V。光伏性能测试显示氟取代使PTTBDT-FBTA基器件的能量转换效率(PCE)提高了49.3%,这获益于开路电压(UOC)提高了16.9%、短路电流密度(JSC)提高了13.2%和填充因子(FF)提高了11.8%。

Two wide bandgap copolymers,PTTBDT-BTA and PTTBDT-FBTA,have been prepared by the Stille coupling polymerization method in the presence of tris(dibenzylideneacetone)dipalladium(Pd 2(dba)3)and tri(o-toyl)phosphine(P(o-tol)3),based on the two dimensional 4,8-bis(5-(2-butyloctyl)thieno[3,2-b]thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene(BDT)as donor(D)moiety,thieno[3,2-b]thiophene(TT)as conjugatedπbridge and benzo[d][1,2,3]triazole(BTA)/5,6-difluorobenzo[d][1,2,3]-triazole(FBTA)as acceptor(A)unit,respectively.Both copolymers were characterized by a set of methods including 1H-NMR,13 C-NMR,elemental analysis,gel permeation chromatography(GPC),thermogravimetric(TG)analysis,UV-Vis absorption and cyclic voltammetry(CV),etc.And the effects of fluorine on thermal stability,film-forming property,absorption spectra,aggregation ability in chlorobenzene(CB)solution,energy level and photovoltaic performance were investigated.Compared with PTTBDT-BTA,PTTBDT-FBTA showed an increase for decomposition temperature(T d,5%mass-loss)of 20℃,decreased solubility,slightly narrowed absorption range,significantly enhanced aggregation in CB solution and a decrease for the highest occupied molecular orbital energy level(E HOMO)of 0.10 eV.The photovoltaic devices were fabricated with a structure of ITO/PEDOT:PSS/active layer/PFN/Al,using PTTBDT-BTA or PTTBDT-FBTA as donor and[6,6]phenyl-C 61 butyric acid methyl ester(PC 61 BM)as acceptor,and their photovoltaic properties were investigated under the AM 1.5,100 mW/cm 2.It was found that the optimal device based on fluorinated PTTBDT-FBTA exhibited a 49.3%increase in power conversion efficiency(PCE),which was originated from a 16.9%enhancement of open circuit voltage(U OC),a 13.2%improvement of short circuit current density(J SC)and a 11.8%rise of fill factor(FF)compared with PTTBDT-BTA-based devices.These results demonstrated that fluorination was an effective strategy for tuning the material structure and improving the photovoltaic property.