Design And Synthesis Of The The Benzoxazolyl Polymer Photovoltaic Materials And Performance

In order to broaden the absorption spectrum of conjugated polymer donor materials, improve their solubility and hole mobility, three new series of new benzoxazolyl conjugated polymers were designed and synthesized in this dissertation. Bulk heterojunction(BHJ) polymer solar cells were fabricated using these conjugated polymers blended with PCBM as active layers. Furthermore the relationship between active layers, morphology and photovoltaic performance were also discussed. The main results are as follows:(1) Three alternating conjugated copolymers, comprised of benzodithiophene(BDT) and 5,6-dioctyloxy-benzothiadiazole(DOBT) derivatives with (0,1,2) thiophene unit, were synthesized via Stille cross-coupling reaction. These copolymers seemed promising for the application in BHJ solar cells due to their good solubility and high hole mobility as well as their low bandgap. The photovoltaic properties of the copolymers were investigated based on the blend of different the polymer/PC71BM weight ratio under AM1.5G illumination at 100 mW/cm2. The device with ITO/PEDOT:PSS/P3:PC71BM(1:2, w/w)/Ca/Al gave the best performance, with a power conversion efficiency of 4.02%.(2) Using 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzothiadiazole (DODTBT) as an electron-deficient moiety and fluorene or 2,7-carbazole as an electron-rich moiety, we synthesized two new low bandgap copolymers with good solubility, P4 and P5, respectively. Combined with P3 from the previous chapter, we investigated different donor moiety effect on photovoltaic properties of such kind of conjugated polymer materials.(3) Four D-A alternating low bandgap copolymers, using 5, 6-bisalkoxylbenzooxadiazole (BX) as an electron-deficient moiety and benzodithiophene or 2,7-carbazole or fluorene as an electron-rich unit, were synthesized and well characterized. The copolymers possess good solubility, high thermal stability, broad absorption as well as low bandgap ranging from 1.52 eV to 1.73 eV. Their electronic and photovoltaic properties can be easily tuned by incorporating different donor moieties into the polymer backbone. The preliminary photovoltaic device based on PBDT-DTBX:PC61BM gave a PCE value of 2.90%, which showed that BX probably is a promising electron accepting building block in organic electronics.