Charge Transfer Of Nano-islands And Fibrils Based On Poly(3-hexylthiophene-2,5-diyl) With Light Modulation

Polymer solar cells has been the focus of the present study because of the characterized of simple process, low cost materials and could be made into flexible products, the research for the main parts of which- polymer has been more and more. In this thesis, the photo-electrical properties of poly(3-hexylthiophene-2,5-diyl)(P3HT) is studied under different nanostructures. The main contents are following:First of all, the two kinds of P3 HT nanostructures- nanoisland and nanofiberils are prepared. Atomic force microscope(AFM) is used to characterize the morphology of P3 HT nanostructure and the difference of molecular arrangement. The statistical histograms of the height of the two different nanostructure show that: The structure of nanoisland is layered and the height of each layer approximately equal P3 HT single-layer thickness(~1.5-1.6 nm), which is applies to the height of nanofibrils. Because of the distorted and folding of the molecular arrangement, the similarity and dissimilarity between P3 HT nano-islands and fibrils are existence.Furthermore, the crystallization properties of nanostructures was characterize by Raman spectrum.The peak height may represents the bond strength of different molecules, and the ratio of different peak height may represents the degree of crystallization of polymer. Compare with the ratio of C-C/C=C intensity, the values of nano-island is bigger than the nano fiberils, which indicates that the crystallinity of nano-island is better than the nano fiberils.Finally, the scanning Kelvin probe microscopy(SKPM) and electrostatic microscopy(EFM) were used to research the impact of light on surface potential and surface charge of the nano-islands and fibrils, respectively. The comparison of surface potential of the two nanostructures between light on and off show that the illumination play a positive role for the increment. Comparing the changes of surface charge between light on and off, the results show that the increase of photo-induced charges for nanoislands and fibrils are around 24% and 15% respectively. The results show that although the increment of charges in nano-islands and fibrils are different light on, the change tendency are consistent,the similar response on illumination shows that the ?-? stacking nature are suitable for both P3 HT islands and fibrils and the P3 HT molecule belong to the structure of hole-conducting, so the molecular arrangement is associated with electrical properties. As P3 HT is hole-conducting molecule, positive charges are found easily injected into single island by a positively biased EFM tip, and then the injected charges are able to propagate all over the island. This also indicates that the good degree of chain planarity in these nano-islands can improve the charge transportation.Above all, we can study the effect of crystalline on electro-optical properties of P3 HT and explore the potential application in photoelectricity and solar cells by atomic force microscope.