A Study On Preparation Of P3HT Nanofibers By Electrospinning And Their Optoelectric Properties

Poly(3-hexylthiophere)(P3HT) is a conjugated polymer with a high chargemobility of0.192cm2V-1s-1and band gap energy of1.9~2.0eV and widely used in photodetectors, light emission diodes, and polymer solar cells as donor materials. The deviceperformance can be improved greatly when combining P3HT and the acceptor materialphenyl-C61-butyric acid methyl eater (PCBM) with high electron mobility to form bulkheterojunction (BHJ) configuration. The present research is aiming at the application ofphoto detector. In this thesis, nanofibers of P3HT and its hybrid with PCBM wereprepared and their preparation process, structure, and optoelectric properties wereinvestigated. SEM, FTIR and XRD were used to characterize the structure, composition,and crystallinity of the obtained materials. UV-visible spectrophotometer, fluorescencespectrophotometer, and semiconductor parameter measuring system were used tomeasure the optical and optoelectric properties of the obtained materials.P3HT and P3HT/PCBM composite nanofibers were prepared by coaxialelectrospinning, where the effects of polymer concentration and the solution supplyingrate on the fiber structure were investigated. SEM measurements indicate that theformation of uniform nanofibers require appropriate solution concentration. Thesolution concentration of3%（wt/v）shows better results when preparing the P3HTnanofibers. During the preparation of P3HT/PCBM composite fibers the mass ratio ofP3HT to PCBM is kept at1:1and the P3HT and PCBM concentrations of3%~6%showbetter results. IR spectra show that P3HT and PCBM were only mechanically mixed inthe fibers and no chemical changes occur. UV-visible absorption spectra indicate thatthe absorption spectra of the composite fibers are only the cumulation of the twopolymers.The composite nanofibers were annealed at50,100,150, and200℃to changetheir crystal structure for investigating the effects of annealing temperature on the fiberperformance. SEM observation indicates that the fiber morphology changes notobviously. XRD measurements indicate that the crystallinity of the fibers was improvedby the annealing. UV-visible absorption spectra indicate that the annealing treatmentcan increase the absorption of the nanofibers. The annealing experiments indicate thatthe fibers annealed at100℃has optimal optoelectric performance.The optoelectric properties were measured using the semiconductor parametermeasuring system and the effects of the addition of PCBM, arranging orientation of thenanofibers, solution concentration and annealing treatment on the optoelectric propertieswere investigated. It is indicated that the optoelectric property of the P3HT/PCBMcomposite fibers improves obviously comparing with the pure P3HT nanofibers and the photo to dark current ratio is four times bigger than P3HT nanofibers. The photo to darkcurrent ratio can reach200, showing a great increase comparing with the randomlyarranged nanofibers. The photo to dark current ratio of the P3HT/PCBM compositefibers after annealing treatment is five times bigger than that without annealingtreatment.