Study On Photovoltaic Properties Of PPV Derivatives And Hyperbranched Conjugated Polymers Containing Thienylenevinylene

With the depletion of non-renewable resources, the use of sunlight has been paid much attention. Polymer solar cells have been widely applied due to its simple preparation, light weight, low cost and large flexible area. The narrow absorption bandwidth of polymeric donor materials is one of the key factors that limit the improving of power conversion efficiency (PCE). The design and synthesis of polymers with broad absorption was an effective way to improve the power conversion efficiency.Poly(p-phenylene vinylene) (PPV) and its derivatives are one of the most promising classes of conjugated polymers for polymer solar cells due to their easy modification of the chemical structure, good film forming and optical properties. The conjugated side chains could broaden the absorption spectrum of the polymers efficiently. In this paper, two novel poly(p-phenylene vinylene) (PPV) derivatives with conjugated thiophene side chains, P1 and P2, were synthesized by Wittig-Horner reaction. The thermal, photophysical, electrochemical, and photovoltaic properties of the polymers were investigated in detail. The absorption spectra of P1 and P2 were broadened and red-shifted effectively in 300-580 nm. Electrochemical measurement displayed that the band gap of the polymers was reduced by attaching conjugated thiophene side chains. The PCEs of the devices based on P1 and P2 are 0.10% and 0.17%, respectively.Hyperbranched conjugated polymers have certain advantages over conventional linear conjugated polymers because of their unique structure. These polymers deserve attention in the field of photoelectronic devices, not only because of their amorphous properties and good solubility in common organic solvents but also because of their twisted intramolecular charge transfer properties. Twisting in hyperbranched conjugated polymers contributes to the efficiency of charge separation and irreversible photoinduced charge transfer, and this reduces the possibility of charge recombination and enhances the quantum efficiency of the nonradiative process. Thus, it may be suitable for applications in polymer solar cells. In this study, a novel hyperbranched conjugated polymer was synthesized via an A3+B2 type Wittig-Horner reaction. The thermal, photophysical, electrochemical, and photovoltaic properties of the polymer were investigated in detail. The absorption spectrum of the polymer showed broad absorption band from 300 nm to 608 nm in solid state. Electrochemical measurement displayed that the band gap of the polymer was 2.01 eV. The PCEs of the device based on the polymer was 0.09%.The results indicate that the side chain and hyperbranched polymers are promising photovoltaic materials for polymer solar cells.