Design,Synthesis Of Novel Conjugated Polymers And Their Applications In Polymer Solar Cells

Polymer solar cells(PSCs) have attracted enormous attention due to their various advantages of light-weight, mechanical flexibility, all-solid, semi-transparent, portability, and solution processing accessible for large-area modules. In recent years, with development of polymer solar cells and in-depth understanding of their inner working mechanisms, more and more efficient materials and devices have been developed. Nowadays, the highest efficiency of single-junction PSCs reported is 11.7%, and the efficiency keeps growing, indicating the promising future for their commercialization. However, high-performance devices prepared under laboratory conditions may not be applicable for the production of high-performance large-area PSC modules. Thereby, the development of stable, efficient, and high-throughput processing available materials is still of particular interests. Herein, we developed series of novel conjugated polymers for the use as active layers and electron transporting layers(ETLs) in PSCs.In charpt 2, we developed a serie of novel acceptor-pended push-pull conjugated polymers with carbazole derivate as structural unit, in which, two phenyl rings of triphenylamine were fused together to achieve a relative planar structure of conjugated main-side chains. The absorption spectra and band gaps of these polymers could be readily tuned by altering the strength of the pendant acceptor groups. Space-Charge-Limited-Current studies of polymer/PC71 BM blend films revealed these new synthesized polymers possessed better hole transport property than their triphenylamine analogues.In charp 3, based on the tranditional acceptor-pended conjugated polymers, we proposed the design of novel conjugated polymers with cross-conjugated D-π-A chromophores, in which we introduced benzodithiophene as building blocks of the main chain, as the result, the resultant polymers possessed deep HOMO levels. Energy levels and the absorption spectrum of polymers could be readily tuned over a wide range by attaching the different donor groups or acceptor groups to side chains of the polymer. Moreover, the UV-visible absorption characterization of these polymers revealed that the different donor groups in the side-chain would also affect the aggregation of the main chain. Ultimately, PSCs based on these polymers exhibited a high Voc of 1.0V.The work in charpt 4 is the extension of the work in charpt 3. In this work, we designed and synthesized the black polymers with D-A main chains and cross-conjugated D-π-A chromophores. The diketo pyrrolo-pyrrole(DPP) unit was introduced to constructed the D-A main chain, which resulted in enhancing light absorption of polymers. Finally, a full visible light absorption property was achieved in the type of polymer.In charpt 5, we designed and synthesized two novel naphthalene diimide(NDI) based n-type water/alcohol-soluble conjugated polymes(WSCPs) PNDIT-F3 N and PNDIT-F3N-Br for ETLs of PSCs. The π-delocalized planar structure with high electron affinity of the NDI unit enable the resultant polymers possessed relative high electron mobility and good energy level alignment when used as ETLs in PSCs. Furthermore, the functional amine or a quaternary ammonium polar group in the side chain allowed these WSCPs having excellent solubility in polar solvents, providing a facial to process ETLs with orthogonal solvents over the broad range of thickness, which is ideal for multilayer devices. Through the scanning kelvin probe microscopy measurment, electron-only devices studies and electron spin resonance spectroscopy tests revealed that both the amine functional group and the quaternary ammonium polar group possessed WF tuning effects with the metal electrode and n-doping effects with the acceptor of the active layer. In addition to the excellent interfacial engineering ability and good solubity in polar solvents, these newly developed n-type WSCPs were allowed to be processed over a broad thickness range of 5 to 100 nm for efficient ETLs of PSCs. Moreover, the ESR studies indicated the self-doping effect inside these WSCPs. In the further studies of photoconductivity measurement, the two WSCPs with different polar moieties showed the different doping mechanisms. Eventually, PSCs based on these WSCPs yields a high PCE of 10.11% in the PffBT4T-2OD/ PC71 BM system with conventional device structure and a prominent PCE of over 8% was also achieved even when the thickness of ETL was over 100 nm.The work of last charpt is extended from the work of previous chapter. The impact of different counter-ions on the thermal, optical, electrochemical, self-doping effect and charge transporting properties of these WSCPs were systematically studied in this charpt.