Conjugated Polymer Synthesis And Properties Of Benzo Thiophene And Aromatic Polyimide

Conjugated polymers have recently attracted considerable attention due to their potential applications in large-area, flexible optoelectronic devices, such as polymer light-emitting diodes (PLEDs), polymer solar cells (PSCs), and organic thin-film transistors (OTFTs), etc. by low-cost solution-processing. To improve the power conversion efficiency of PSCs, conjugated polymers should have narrow bandgaps and deep HOMO energy levels. In this dissertation, based on molecular design, four novel conjugated polymers have been synthesized via the alternative copolymerization of the electron-donating monomer benzodithiophene (BDT) and four different electron-accepting monomers:perylene diimide (PDI), naphthalene diimide (NDI), and phthalimide (PhI) and phthal diimid (PhDI). Herein we successfully got four new polymer semiconductor materials, P(BDT-PDI), P(BDT-NDI), P(BDT-PhDI) and P(BDT-PhI).The thermal, optical and electrochemical properties of the four polymers were studied by TGA, optical absorption spectra, and cyclic voltammetry. The differences of the properties among the polymers were discussed. The relationship between the molecular structure and the semiconductor behavior of the polymers was investigated. All obtained copolymers show broader absorptions in visible region and narrower optical band gaps compared to homopolymers from BDT units. Cyclic voltammograms of the four polymers disclose that P(BDT-PDI) and P(BDT-NDI) are typical n-type materials and P(BDT-PhI) is a stable p-type material, while P(BDT-PhDI) exhibits both p-type and n-type properties.The four polymers were used as active layers to prepare bulk heterojunction solar cells. The photovoltaic properties of the polymers were studied and the highest energy conversion efficiency of 0.53% was achieved in the P(BDT-PhI)-based device.