Synthesis And Photovoltaic Properties Of Fused-ring Aromatic Lactone Polymer Donor Materials

Compared with crystalline silicon photovoltaic cells,organic solar cells(OSCs)possess the characteristics like light weight,low cost,large-scale fabrication,flexibility and solution processing,which has attracted extensive attention from the scientific community.The research of copolymer donor materials has always been a research hotspot of active layer materials.This thesis focused on the development of copolymer donor materials,featured with D-A(electron donor-electron acceptor)configuration with a tricyclic thiolactone unit or a pentacyclic bislactone unit as the electron acceptor unit,and the correlation between the structure of the active layer material and the device performance.The research contents are as follows:(1)A tricyclic thiolactone unit DTTP was synthesized through condensation,bromination,Stille coupling,dealkylation,acidification,and transesterification starting from 3-bromothiophene and 2-ethylhexyl-3-mercaptopropanoate.DTTP underwent bromination,Stille coupling,and another bromination,and finally copolymerized with BDT-Sn with a two-dimensional spatial structure in the presence of two types of catalyst to obtain the target copolymer donor D16 with the tricyclic thiolactone unit as electron acceptor unit.The optical and electrochemical properties of D16 were studied,and the results showed that the optical band gap and HOMO energy level of D16 were slightly reduced compared to the copolymer donor L1 with a tricyclic lactone unit as electron acceptor unit.The active layer material was prepared by blending D16 with the acceptor material Y6 which is featured with a planar structure containing an A2-D-A1-D-A2 trapezoidal condensed ring,by optimizing the D/A ratio,additives,and film thickness,and the highest PCE of 16.72%obtained with V_oc value of 0.85 V,J_sc of 25.41 m A/cm²and FF of 74.9%.Its device performance was better than L1:Y6-based device.(2)Starting from(3,4-dimethoxythiophene-2,5-diyl)bis(trimethylstannane)and2-ethylhexyl 2-bromothiophene-3-carboxylate,a planar structured pentacyclic bislactone unit BL1-Br was synthesized via Stille coupling,bromination,demethylation and transesterification.The 2,5-dibromothiophene-3,4-dicarboxylic acid as a starting material lead to a twist-structured pentacyclic bislactone unit BL2-Br via esterification,Stille coupling,bromination,demethylation and transesterification.BL1-Br and BL2-Br were respectively coupled to the?bridge and then underwent bromination and finally copolymerized with BDT-Sn with a two-dimensional spatial structure in the presence of two types of catalyst to obtain the target copolymer donor P1 with a planar structured pentacyclic bislactone unit as electron acceptor unit and P2 with a twist-structured pentacyclic bislactone unit as electron acceptor unit,respectively.The optical and electrochemical properties of P1and P2 were studied,and the results showed that the optical band gap and HOMO energy level of P1 and P2 were reduced compared to L1.P1 and P2 were blended with the acceptor material IT-4F with a planar structure containing an A-D-A trapezoidal condensed ring by optimizing the D/A ratio,additives,and film thickness for the preparation of the active layer material of the polymer solar cell device.The PCE of the P1:IT-4F-based device was found to be 10.44%with a high V_oc value of0.96 V,and the device results of P2 were found to be inferior to those of P1.