Synthesis And Photovoltaic Properties Of Organic Photovoltaic Materials Consisting Of Benzo[1,2-b:4,5-b’]dithiophene，Isoindigo, Benzothiadiazole And Triphenylamine

The exhaustible nature of conventional energy resources and their detrimentalimpact on our environment boost the need for low-cost, efficient, clean, renewableenergy alternatives, so organic solar cells (OSCs) has become arguably one of thehottest topic in academia and industry. In recent years, although its steady advances inthe effciencies, the power conversion efficiency (PCE) of the OSCs needs to beimproved for future commercial applications.1. Two novel side-chain polymers (PBDT-HTID and PBDT-TID) and thecorresponding main-chain polymers (PBDT-HTIDHT and PBDT-TIDT) containingbenzo[1,2-b:4,5-b′]dithiophene (BDT) and isoindigo (ID) moieties were designed andsynthesized. Their thermal, photovoltaic properties, electrochemical andphotophysical were studyed contrastively and systematically. The introduction ofisoindigo-2-vinylthiophenyl unit into conjugated side chain exhibited optimalmorphology in active layers and favorable molecular geometries. Hence bulkheterojunction polymer solar cells fabricated from PBDT-TID and PC61BM showedthe promising power conversion efficiencies of5.25%and6.51%using aconventional and inverted device structures, respectively.2. Three new organic small molecules (TPA-DTBT, TPA-DTBT-TH andTPA-DTBT-CAO) containing triphenylamine (TPA) and4,7-bis(thiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT) moieties with different terminal groups, weredesigned and synthesized. Their photovoltaic properties, photophysical, thermal andelectrochemical were studyed. The introduction of2-ethylhexyl cyanoacetate and2-tetradecyl thiophene as terminal groups extended molecular π-conjugation lengthand broadened the absorption spectra. In solvents, three small molecules exhibit goodfilm-formming ability and solubility, and themal stability. Bulk heterojunction (BHJ)solar cells based on the blend of small molecule TPA-DTBT and PC61BM showed apower conversion efficiency (η) of1.85%.3. A novel branchlike organic dyes (WD1) based on4,7-bis-(4-hexylthiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT), containing vinylenes as π-conjugated unit, wasdesigned and synthesized for dye-sensitized solar cells (DSSCs). The effects of DTBTon the photovoltaic properties, photophysical and electrochemical of dye wassystematically studied. Compared to our previous study (FD1and D2), the introduction of DTBT unit into the WD1molecule leads to a remarkably red-shiftedabsorption and lower molar extinction coefficient. The DSSCs based on WD1dyeexhibited the lower η of2.18%.