基于吡啶四噻吩和苝二酰亚胺材料的合成及性能

Synthesis and Properties of Electron Receptor Material Based on Pyridine and Perylene Diimide

以吡啶环为中心,在吡啶环的2,3,5,6位各键接一个噻吩为π桥,将其与四个苝二酰亚胺通过bay位进行Stille偶联,得到一种新型“螺旋桨状”不对称PDI基非富勒烯电子受体材料Py-4PDI。Py-4PDI在波长为300~650 nm段有强吸收,而PTB7-Th在500~800 nm波段有强吸收,故Py-4PDI与PTB7-Th的吸收光谱有较好互补性。Py-4PDI最高成键分子轨道能级为-6.05 eV,最低空轨道能级为-4.11 eV,其能级与PTB7-Th的能级满足电荷分离、转移的要求。虽然Py-4PDI呈现“螺旋桨状”扭曲能抑制分子中PDI自身聚集,但使PTB7-Th:Py-4PDI共混活性层膜相分离严重,致使电荷传输性能较差,其电子迁移率仅为1.18×10^-4 cm^2·V^-1·s^-1,导致其器件的Jsc和FF较低。此外,PTB7-Th与Py-4PDI之间HOMO能级差为0.85 eV,导致所制备的本体异质结型有机聚合物太阳能电池器件在光电转换过程中能量损失(Eloss)较大,致使器件光电转换效率仅为3.32%。但这是目前报道基于PDI不对称NFAs最高的效率。

A novel asymmetric small molecule Py-4PDI was designed and synthesized by using the electron-deficient pyridine ring as the core,four perylene diimide as four arms,in which four thiophenes were used to connect with the core at 2,3,5,6 sites and the arms at the bay positions.Py-4PDI shows strong absorption in the waveband between 300 nm and 650 nm,which is complementary with the absorption spectrum of PTB7-Th(500~800 nm).The HOMO(highest occupied molecular orbital)and LUMO(lowest unoccupied molecular orbital)energy levels of Py-4PDI are-6.05 eV and-4.11 eV respectively,which meet the energy requirements for charge transport.Although the twisted Py-4PDI molecule can impede the aggregation of PDI itself,the phase separation of PTB7-Th:Py-4PDI blend is serious,which lead to the bad performance of charge transfer.The weak electron mobility(1.18×10^-4 cm^2·V^-1·s^-1)results in the lower Jsc and FF.In addition,the larger difference(ΔEHOMO(D-A)=0.85 eV)of HOMO between donor PTB7-Th and acceptor Py-4PDI which caused greater energy loss(Eloss),and the PCE is only 3.32%.This is the highest PCE based on PDI asymmetric NFAs.