Rational Molecular Design,Materials Synthesis And Photovoltaic Application Of N-type Conjugated Polymers Based On Naphthalene/Perylene Diimide

Since American scientist Alan. J. Heeger found conductive polymer, materials and device conversion efficiency of organic polymer solar cells received a lot of attention in academic and industry research. The active layer materials is composed of donor-polymer and acceptor-fullerene derivatives blending in common organic solar cells(OPV). In recent years, it has got much academic attention due to constant breakthrough in power conversion efficiency and many superior performances when comparing acceptor polymers with fullerene derivative. The thesis summarizes molecular synthesis of N-type copolymers based on naphthalene/perylene diimide(NDI/PDI), and mainly studies the correlation between polymers performance and photovoltaic devices. Main contents are as follows:1. By the introduction of different building blocks and side-chains, a series of Donor-Acceptor(D-A) type polymer acceptors containing naphthalene diimide(NDI) have been successfully prepared. The theoretical and experimental results showed that our molecular design effectively tuned the energy levels, solubility, and coplanarity of the acceptor polymers. The intermolecular packing, which has been considered as a key factor in the bulk heterojunction morphology, has been adjusted by changing the coplanarity. As a result of improved morphology and fine-tuned energy levels, we demonstrated a power conversion efficiency(PCE) of 6.01 % for the optimized devices, which is among the highest-efficiencies for reported all-polymer solar cells. The improved device performance may be attributed to the resemble crystallinity of the donor/acceptor polymers, which can lead to the optimal phase separation morphology balancing both charge transfer and transport. It will be beneficial for our selecting proper acceptor polymer.2. We paid less attention and made little research on acceptor polymers based on perylene diimide(PDI). So we chose the structure PDI-T and alternated three different length side chains to study the influence with different side chains. What’s more, we change thiophene with selenophene. From the photovoltaic results, we got a better PCEs up to 2.2%. We conclude the alky-side chains and D-unit in polymer structure, which will influent the morphology and transport. But more characterizations and measurements should be tested.3. We designed and synthesized a new novel polymer, which will be beneficial for tuning phase separation size.Through the research of this paper, we can give some guidance and reference for the future molecular design and synthesis in N-type copolymers based on NDI/PDI. What’s more, we can design new novel polymers for no additive and no annealing in solution-processed.