Design,Synthesis And Photovoltaic Application Research Of Perylene Diimide Cathode Interface Materials

In recent years,the research of organic solar cells（OSCs）has developed rapidly,and the power conversion efficiency（PCE）has exceeded 19%.In addition to the important active layer materials,excellent interface layer materials are also necessary,so it is of great significance to develop efficient interface layer materials.In this study,we designed and synthesized a class of perylene diimide based cathode interface material for the defects of the cathode interface materials.Specific research contents are as follows:1.Design,synthesis and application of bay-functionalized perylene diimide cathode interface materials.We choosed perylene diimide as the main structure,and 2,6-diisopropyl phenyl was introduced into the imide N to ensure the solubility of the molecule.An aliphatic amine chain with an amine polar group was introduced in bay-positions to enhance the solubility of the molecule in the polar solvent and reduce the work function of the electrode.Two small molecules（2N-PDI,2NBr-PDI）were obtained through a six-step synthesis including esterification,nucleophilic substitution,dehydration,amidation,and quaternization.Each step of the synthesis reaction has a high yield（>40%）,and the synthetic total yield was 4.5%.Using them as cathode interface materials,they are applied to bulk heterojunction organic solar cells.The results show that the two molecules have lower LUMO energy levels（-3.88e V,-3.97 e V）,and high 5%weight loss temperature（T_d>180℃）,strong work function reduction ability,self-doping performance,and good solubility in polar solvents such as methanol（higher than 1 mg/m L）.The device with 2NBr-PDI as the cathode interface layer shows a higher electron mobility(3.1×10^-4cm²V^-1s^-1).With PM6:Y6 blends as active layer,and 2NBr-PDI as cathode interface layer,the power conversion efficiency of organic solar cell devices can reach 16.18%,and the fill factor can to 78.37%.2.Design,synthesis and application of a small molecule cathode interlayer of semi-perfluoroalkylated perylene diimides.Perylene diimides was used as the main structure and a semi-perfluoroalkylated chain was introduced on its imide N to enhance the solubility,crystallinity,and carrier mobility of the molecule.An aliphatic amine chain with an amine polar group was introduced in bay-positions to enhance the solubility of the molecule in the polar solvent,and reduce the work function of the electrode.Two target molecules（2N-C6F4-PDI,2NBr-C6F4-PDI）were synthesized by four steps of amidation,nucleophilic,substitution,and quaternization.Each step of the synthesis has a high yield（>35%）,and 10%of the total synthetic yield.Using the two as cathode interface materials,they are applied to bulk heterojunction organic solar cells.The experiment results show that they have suitable LUMO energy levels（-3.76 e V,-3.8 e V）,and high 5%weight loss temperature（T_d>180℃）,has good solubility in polar solvents such as methanol（higher than 1 mg/m L）.With PM6:Y6 as the active layer and 2NBr-C6F4-PDI as the cathode interface layer,the power conversion efficiency of organic solar cell devices reaches 13.86%.