Synthesis And Properties Of Organic Photovoltaic Materials Based On Benzo Thiadiazole And Diketopyrrolopyrrole Groups

The research status of the organic photovoltaic electron donor materials and their bulk heterojunction (BHJ) organic solar cells were summarized in this dissertation. The synthesis and properties of organic photovoltaic electron-donor materials based on benzothiadiazole and diketopyrrolopyrrole groups were studied in order to solve the key issues, such as low sunlight absorption efficiency and bad carrier-transporting efficiency for organic photovoltaic materials. The made organic photovoltaic electron donor materials exhibit donor(D)-acceptor(A)-donor(D) or acceptor(A)-donor(D)- acceptor(A) structures. The molecular structures of these organic photovoltaic electron-donor materials were characterized by 1H NMR and MALDI-TOF MS. Their thermostable, photophysical, electrochemical properties were studied by thermo- gravimetric analysis, UV-vis absorption and photoluminescence (PL) spectra, as well as cyclic voltammograms. Furthermore, the photovoltaic properties were further inves- tigated by BHJ organic solar cells. The main study results are listed below.1. The organic photovoltaic electron-donor materials of C1-C6 with a D-A-D structure exhibited excellent thermal stability, which contain an acceptor unit of benzo -thiadiazole or diketopyrrolopyrrole, and two donor units of fluorene, triphenyl- amine and carbazole. The D-A-D-based organic photovoltaic electron-donor materials of C1, C2 and C3, which contain an acceptor unit of benzothiadiazole, as well as the materials of C4, C5 and C6, which contain an acceptor unit of diketopyrrolopyrrole, displayed similar UV absorption and PL spectra, respectively. Among these D-A-D- based organic photovoltaic electron-donor materials, the C2 and C5 with a donor unit of triphenylamine showed a wider absorption spectrum and a red-shifted PL spectrum. The C1 with an acceptor unit of benzothiadiazole and a donor unit of fluorene, and the C5 with an acceptor unit of diketopyrrolopyrrole and a donor unit of triphenylamine showed better photovoltaic performance. The energy conversion efficiency (PCE) of the BHJ organic solar cells based on a blend of C1(or C5) and PCBM reached 1.39% and 1.18%, respectively.2. The organic photovoltaic electron-donor materials of C7-C10 with an A-D-A structure, which contain two acceptor units of benzothiadiazole and a donor unit of fluorene or carbazole, also exhibited excellent thermal stability, as well as similar UV absorption and PL spectra. Among these A-D-A-based organic photovoltaic electron- donor materials, the C7 and C8 with a donor unit of carbazole showed a red-shifted UV absorption and PL spectra. The C8 with 3,6-carbazole group presented better photovoltaic performance. The PCE of the BHJ organic solar cells based on a blend of the C8 and PCBM was 0.38%.3. The photovoltaic performance of the organic photovoltaic materials can be affected by the connected way of donor and acceptor units. The D-A-D-based organic photovoltaic electron-donor materials exhibited better photovoltaic performance than the A-D-A-based ones. This work provides a significant effect on the design of new organic photovoltaic materials and the further study between structure and properties.