基于3,4-二氰基噻吩的宽带隙共轭聚合物的设计合成与光伏应用

Design and Synthesis of Wide-bandgap Conjugated Polymers Based on 3,4-Dicyanothiophene for Efficient Organic Solar Cells

利用3,4-二氰基噻吩(DCT)为电子受体单元,苯并双噻吩(BDT)为电子给体单元,并结合不同侧链取代的噻吩为π桥,设计合成了一系列新型宽带隙共轭聚合物:PB3TCN-C32、PB3TCN-C36、PB3TCN-C36-R以及PB3TCN-C40.这些聚合物具有较宽的光学带隙(>1.8 eV)、较深的最高占有分子轨道(HOMO)能级.与非富勒烯受体(IT-4F)结合制备了有机太阳电池器件,其中聚合物PB3TCN-C40实现了高达11.2%的能量转换效率(PCE),其开路电压(Voc)为0.92 V,短路电流密度(Jsc)为18.9 mA cm-2,填充因子(FF)为0.64,是目前文献报道基于氰基噻吩类聚合物材料的最好结果.同时,该体系具有低至0.6 eV的能量损失.这些结果表明DCT是一种极具潜力的实现宽带隙、深HOMO能级共轭聚合物的构筑单元,有望实现更高能量转换效率的有机太阳电池.

In this contribution,we report a set of wide bandgap conjugated polymers(PB3TCN-C32,PB3TCNC36,PB3TCN-C36-R,PB3TCN-C40)based on 3,4-dicyanothiophene(DCT)for use as electron donors in organic solar cells(OSCs).The polymers exhibit wide optical bandgaps(>1.8 eV)and deep highest occupied molecular orbital(HOMO)levels due to the high electron affinity of DCT unit.The optoelectronic properties,active layer morphology,and device performance of the polymers can be tuned by side chains.As a result,high-performance solar cells with a decent power conversion efficiency(PCE)of 11.2%have been achieved by PB3TCN-C40 when using IT-4 F as the electron acceptor.Noticeably,the polymers afforded a high open circuit voltage(Voc)of up to 0.92 V and an energy loss(Eloss)as low as 0.6 eV even though there is not any additional withdrawing groups such as F,Cl,or S atom on the polymers,which is superior to the leading polymer donors in the field of OSCs.These results suggest that the DCT unit hold big room for further increasing Voc and decreasing Eloss of OSCs via rational polymer design,which is desirable for application in tandem devices and in-door photovoltaics.Overall,this work demonstrated that DCT is a promising building block for constructing wide bandgap conjugated polymer with deep HOMO level for highly efficient OSCs.