The effects of one-dimensional (1D) and two-dimensional (2D) π-conjugation extensions of donor–acceptor (D–A) copolymers on their intrinsic and photovoltaic properties in ternary-blend organic solar cells (OSCs) were investigated systematically by using one polymer donor and two acceptors (PC71BM, ITIC). A series of wide bandgap D–A copolymers (PBT-OTTs) were synthesized based on the benzo[1,2-b:4,5-b′]dithiophene (BDT) unit and the thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) unit, which extend in the backbone (1D) and side-group directions (2D) respectively from the PBT-OTT backbone. These copolymers are PBT-OTT (the parent polymer), PDTBT-OTT (with a 1D backbone extension consisting of dithieno[2,3-d; 2′,3′-d′]benzo[1,2-b; 4,5-b′]dithiophene), PTTBT-OTT (with a 2D side group extension consisting of 2-alkyl thieno[3,2-b]thiophene (TT)), and PBTBT-OTT (with a 2D side group extension consisting of 2-alkyl benzo[b]thiophene (BT)). Light absorption is significantly increased in the case of PBTBT-OTT due to its extended 2D π-conjugation length and high crystallinity. This increase results from the extended delocalization length and the increased absorption coefficient α of PBTBT-OTT. The wide bandgap polymer PBTBT-OTT has the highest α of the series, so the complementary absorption of the low bandgap ITIC means that the ternary-blend OSCs based on PBTBT-OTT exhibit the highest J_SC = 16.61 mA cm⁻² and PCE = 8.61%. We believe that these findings provide systematic guidelines for the π-conjugation extension of conjugated polymers and thus the design of high-efficiency ternary-blend OSCs.

通过三元体系有机太阳能电池（OSC）系统研究了供体-受体（DA）共聚物的一维（1D）和二维（2D）π共轭扩展对其内在和光伏特性的影响。使用一个聚合物供体和两个受体（PC71BM，ITIC）。基于苯并[1,2-b：4,5-b']二噻吩（BDT）单元和噻吩并[3,4-c]吡咯，合成了一系列宽带隙DA共聚物（PBT-OTTs） -4,6（5H）-二酮（TPD）单元，分别从PBT-OTT骨架在骨架（1D）和侧基方向（2D）上延伸。这些共聚物是PBT-OTT（母体聚合物），PDTBT-OTT（一维骨架扩展由二噻吩并[2,3-d; 2'，3'-d']苯并[1,2-b; 4， 5-b']二噻吩），PTTBT-OTT（具有由2-烷基噻吩并[3,2-b]噻吩（TT）组成的2D侧基扩展）和PBTBT-OTT（具有由2-烷基苯并[b]噻吩（BT）构成的2D侧基扩展）。在PBTBT-OTT的情况下，由于其2Dπ共轭长度延长和高结晶度，光吸收显着增加。这种增加从扩展离域长度结果和增加的吸收系数α的PBTBT-OTT。宽带隙聚合物PBTBT-OTT具有该系列中最高的α，因此低带隙ITIC的互补吸收意味着基于PBTBT-OTT的三元混合OSC表现出最高的J _SC  = 16.61 mA cm^-2和PCE = 8.61％。我们相信这些发现为共轭聚合物的π-共轭延伸提供了系统的指导，从而为高效三元共混物OSC的设计提供了指导。