Design, Synthesis And Properties Of Photoactive Donor/Acceptor Double-Cable Conjugated Polymer

Polymer solar cells (PSCs) have been attracting much attention in recent years because of using conjugated conducting polymers as photoactive materials and the facility of large-area, flexible and low-cost fabrications. One of the important factors determining the performance of PSCs is the properties of the donor (conjugated conducting polymers) and acceptor (fullerene derivatives) materials, while the key issue for the design of the photoactive materials of PSCs is the compatibility and energetic matching of the donor/acceptor materials as well as the manipulation of their phase separation. In this dissertation, motivated by the synthesis of novel fullerene/conjugated polymer intermolecular heterojunction complexes, we have carried out the following works:(1) A novel type of donor/acceptor branched disubstituted polyacetylenes PAs (PA-C60) bearing C₆₀ and pentyl moieties in side chains were synthesized successfully, for which the electronic and optical properties and surface morphology of the thin film were studied. Our results indicated that PA-C₆₀ was qutie soluble in common solvents. For the first time we found that the polymerization of the disubstituted monomer was significantly accelerated by C₆₀ pendant and could be finished within very short reaction time (up to 1.5 min). We proposed a plausible interpretation for this phenomena.(2) A novel type of soluble donor-Ï€-acceptor double cable P3HT bearing C₆₀ pendant with tunable donor/acceptor ratio was synthesized via a facile three-step postpolymerization functionalization of P3HT. A phenyl group was integrated as the linking bridge of P3HT donor and C₆₀ acceptor. The molecular structure, electronic property and thin film surface morphology of the synthesized C60-Ph-P3HT were characterized. Compared to the pristine P3HT, the fluorescence intensity of C60-Ph-P3HT was found to be dramatically quenched (up to 98%). The AFM measurements on the surface film morphology of C60-Ph-P3HT reveal the increased rms roughness compared to that of P3HT. Accordingly, we proposed that C60-Ph-P3HT may become a promising photoactive material in PSCs.(3) A novel pyrene-functionalized poly(3-hexylthiophene) (P3HT) derivative (Pyrene-P3HT) has been successfully synthesized via postpolymerization approach, and was applied for the noncovalent functionalization of single-walled carbon tubes (SWNTs) affording the SWNT/Pyrene-P3HT composite, for which the noncovalent interactions between SWNTs and Pyrene-P3HT were studied in detail. The UV-vis, Raman spectroscopies and ESR spectroelectrochemical study have revealed the electronic interaction between P3HT and SWNTs through the pyrene unit. The fluorescence spectroscopy of SWNT/Pyrene-P3HT indicated a nearly 100% quenching of the fluorescence intensity compared to the reference Pyrene-P3HT, suggesting the a strong photo-induced electron transfer resulting from the noncovalent linkage of SWNTs to the P3HT backbone via the pyrene bridge. SEM and TEM studies on the film morphology of SWNT/Pyrene-P3HT shows that SWNTs are well dispersed in THF by Pyrene-P3HT.