Self-assembly And Optoelectronic Application Of Poly (3-hexyl Thiophene) And P3HT-containing Block Copolymer

Due to the rigid backbone and strong intermolecular interaction,?-conjugated polymers have superior crystallizability and optoelectronic properties,attracting considerable interests in their utilization in various optoelectronic devices.Here we focus on ?-conjugated poly(3-hexyl thiophene)(P3HT)and aim to explore the interaction between P3HT and carbon nanotubes(CNTs),the self-assembly structure of P3HT and the application of P3HT-containing amiphiphilic block copolymer as donor material in fabrication of aqueous-processed solar cells.Straightened CNTs are beneficial to the properties and performance of the CNT-containing materials and devices.We found that straightening of the bent single-walled carbon nanotubes(SWCNTs)could be achieved by forming a centipede-like SWCNTs/P3HT supramolecular structure at low SWCNT concentrations and large SWCNT/P3HT mass ratios.X-ray photoelectron spectroscopy(XPS),ultraviolet-visible absorption spectroscopy(UV-vis)and photoluminescence spectrascopy(PL)revealed that there was a strong ?-? interaction between P3HT chains and SWCNTs,accounting for the increased persistence length of SWCNTs.It was also demonstrated that the straightening effect originated from the rigid P3HT chains adsorbed on the surface of SWCNTs,instead of the epitaxial P3HT crystals.However,the straightening force exerted by P3HT chains is relatively weak and can be counteracted by entanglement and bridge among SWCNTs,which usually occur at a high SWCNT concentration and a low SWCNT/P3HT mass ratio.Moreover,less flexible MWCNTs cannot be straightened by P3HT.Controlling the morphology of conjugated polymers from nanoscale to macroscopic scale remains a key problem for their electronic applications.Here,the assembly of conjugated P3HT chains into ordered nanowires at three-phase interface was achieved via simple deposition of P3HT solution onto an inclined substrate.The experimental conditions affecting polymer crystallization were optimized to enhance the regularity of nanowire growth.P3HT chains are mostly 'edge-on' with the backbone orientation perpendicular to the nanowires,as characterized by grazing-incidence small-angle X-ray scattering(GI-SAXS)and polarized UV-vis.The aligned nanowires,as a conductive network,have a great impact on the carrier mobility as characterized in FET devices.The molecular ordering of polymer chains,unidirectional alignment and dense packing of nanowires facilitate the formation of efficient carrier transport pathway.Considering the simplicity and large-scale alignment,the assemly method of conjugated polymers used in the present work possesses a great potential in the electronic applications.Due to the chemically distinct polymeric segments that are joined together covalently,amphiphilic block copolymers(ABCPs)can self-assemble into ordered structures.P3HT is semiconductive conjugated polymer,so P3HT-containing ABCPs should have favorable optoelectronic properties.Here,poly(3-hexyl thiophene)-b-poly(acrylic acid)(P3HT-b-PAA),homo-P3HT and water-soluble CdTe nanocrystals(NCs)were synthesized and then used to fabricate hybrid solar cells(HSCs)via aqueous process.We found that ABCPs could self-assemble into spherical or cylindrical micelles in water,which then transform into nanowires by co-micellization with homo-P3HT additives.The micelles were applied in the fabrication of aqueous-processed HSCs together with CdTe NCs.After annealing,the hybrid materials formed an interpenetrating network,which resulted in a maximum power conversion efficiency of 4.8%in the HSCs.The properties of the hybrid materials and the film morphology were studied and correlated to the device performance.Aqueous-processed HSCs based on the ABCPs and NCs provide a facile and feasible protocol to fabricate efficient solar cells in a clean and low-cost way.