Synthesis And Photovoltaic Properties Of D-A₁-D-A₂ Polymers Based On Diketopyrrolopyrrole

The design, synthesis and optoelectronic properties of photovoltaic materials based on D-A1-D-A2 polymer have not get enough attention. We designed and synthesized two systems of these polymers to obtain highly efficient polymer solar cells(PSCs) in this paper. At the same time, the regular polymer materials are appeared as a new type organic photovoltaic materials and these polymers have some advantages, such as regular structure, high efficiency, compared to their corresponding random materials. Therefore, we designed and synthesized a regular terpolymer and its corresponding random polymer. The optical, electrochemical, and photovoltaic properties of these copolymers were investigated in detail. The main research work was showed as follows:1. We designed and synthesized three D-A1-D-A2 polymers, PTFB-DPP, PBT-DPP and PNT-DPP, which contain the same donor unit(D) and acceptor unit(A2) unit but different A1 units of tetraflorobenzene(TFB), benzothiadiazole(BT) and naphthothiadiazole(NT). The effect of different A1 on the optical, electrochemical, and photovoltaic properties of these copolymers was investigated in detail. Results showed that the electron-withdrawing ability of A1 is stronger, the absorption spectrum of the polymers is wider, the bandgap is narrower and HOMO energy level is lower. The best power conversion efficiency(PCE) of PSCs based on PTFB-DPP, PBT-DPP and PNT-DPP is 1.41%, 1.41% and 0.04%, respectively.2. Three D-A1-D-A2 copolymers of PTFB-DPP, PDFB-DPP and PB-DPP, with the same of D and A2 units but different A1 of TFB, diflorobenzene(DFB), benzene(B) were designed and synthesized. The effect of the number of F atom into A1 on the optical, electrochemical and photovoltaic properties of these copolymers was investigated in detail. The results showed that the number of F atom is more, the electron-withdrawing ability of A1 is stronger, the absorption spectrum of the polymers is wider, the bandgap is narrower and HOMO energy level is lower. The best PCE of PSCs based on PTFB-DPP, PDFB-DPP, PB-DPP is 4.93%, 5.31%, 4.13%, respectively.3. We designed and synthesized a regular terpolymer P1 containing EHBDT, ODBDT and DPP units and the corresponding random P2. The optical, electrochemical and photovoltaic properties of the two copolymers were investigated and compared in detail. P1 has a more orderly structure and low HOMO energy level compared with P2. The PCE of the regular polymer P1 and the random material P2 is 1.53% and 2.25%, respectively.