Design And Synthesis Of Non-Fused Ring Electron Acceptors And Their Application In Organic Solar Cells

Solar cells,as the technology that transforms inexhaustible solar energy into electricity through photovoltaic effect,have drawn considerable attention from academia and industry,because they present some advantages,such as light weight,easy preparation,low cost,mechanical flexibility and capability to be fabricated into large area.The active layer is composed of electron donor and electron acceptor,which is the core structure of organic solar cells,performs photoelectric conversion.In this paper,we focus our concentrates on electron acceptors.A series of non-fused ring electron acceptors were designed and synthesized,and the acceptors were applied to bulk heterojunction solar cells and single-component organic solar cells,respectively.The photovoltaic properties based on non-fused ring electron acceptors were characterized.What’s more,the relationship between the performance of devices and structure of materials was explored.The specific research content is as follows:1.Three A-D-A type non-fused ring electron acceptors were designed and synthesized by using CPDT as the electron-donating core unit and IC-2F as the electron-withdrawing end-group unit,named CPIC-1,CPIC-2,CPIC-3,respectively.The three acceptor molecules were respectively blended with the donor polymer PBDB-T to prepare bulk heterojunction organic solar cells and exhibited high efficiencies.The power conversion efficiency of the organic solar cell based on PBDB-T:CPIC-2 reached 10.01%,and its external quantum efficiency reached 0.7,while the device performance based on PBDB-T:CPIC-1 and PBDB-T:CPIC-3 were respectively Only 0.63%and 1.71%.In order to explore the reasons for the performance differences,the energy levels,charge transport properties and microscopic morphology of the three small molecules were characterized.We note that the molecule CPIC-2 has a more balanced electron/hole bipolar transport mode,the energy level matched with PBDB-T well,and the blend film has good microscopic morphology and phase separation.2.An A-D-A’-D-A type small molecule LK-128 was designed and synthesized based on the electron acceptor DOC2O6-2F,as a side chain of the double cable conjugated polymer P-16,whose backbone is similar to the donor polymer J-52.The P-16 was applied to single-component organic solar cells,resulting in an open circuit voltage of 0.82 V,the short-circuit current density is 12.18 m A/cm~2,the fill factor is 36.56%,and the power conversion efficiency is 3.66%.It is important to find out the reason why the fill factor is blow 40%.The AFM and GIWAXS showed that after introducing the small molecule LK-128 into the polymer P-16,its original crystallinity and stacking morphology is transformed into an isotropic amorphous state due to the influence of the donor backbone,which makes the stacking morphology of the active layer film based on P-16 become worse,finally resulting in Performance of solar cell devices.