| Water-alcohol soluble conjugated polyelectrolytes(WSCPs)are widely used in polymer solar cells(PSCs),organic thin film transistors(OTFTs),organic light emitting diodes(OLEDs)and biosensing due to their unique solubility and semiconductive characteristics.WSCPs are composed of?-conjugated skeletons and high-polarity functional groups with excellent solubility in environmentally friendly solvents(water-alcohol),thereby good for manufacturing large-area solar cells and improving their photovoltaics performance through environmentally friendly means.In recent years,researchers have summarized the development of WSCPs and investigated their application in different fields.Basically,the synthesis of WSCPs depends on backbone and side chain.Through unique modification of the backbone and fine control of the side chains,the application of WSCPs can be further enhanced.Recently,several reports have been published that the CPEs can endorse the compatibility between the active layer materials and the cathode materials(CILs),resulting in better contact,lower energy barriers,and improved device performance.The side chain engineering has directed the route for synthetic chemists to develop novel materials with excellent charge mobility and has an important influence on physical properties such as energy level,absorption spectrum,emission spectrum,and molecular accumulation.Therefore during the synthesis of conjugated polymers,side chain selection is as essential as the backbone.Recently,the organic device performance has been well improved in PSCs,OEFTs and OLEDs by using doping methods of charge separation.In organic semiconductors the fundamental working mechanism of doping is comparable to inorganic semiconductors.Doping is a remarkable process to modify the charge carrier density of polymers and then to enhance transport abilities and further reduce the Ohmic lose.Holding appropriate energy levels and powerful light harvesting ability is the key requirement to obtain high photocatalytic hydrogen rate(HER).Moreover,organic materials(such as conjugated polymers)have weak mobility and small exciton diffusion length,resulting to much more recombination rate of carrier charges and thus limiting the photocatalytic activity.The structural nature of CPEs allow feasible formation of homogeneous water splitting photocatalytic system,which is conducive to solve the adverse effects of the exciton diffusion process.Additionally,the CPEs have tremendous photostability,which brings another advantages to its wide application in the field of photocatalysis.In Chapter 2,we designed,synthesized and characterized a series of water-soluble alcohol hyperbranched polyelectrolytes,which can be used as both cathode interfacial materials(CIMs)in polymer solar cells(PSCs)and as organic photocatalysts for hydrogen or oxygen evolution.Hyperbranched polyelectrolytes(HD-Br,HN-Br and HP-Br)were quaternisation-polymerized from a 1,3,5-tri(IV rimethy-4-yl)benzene and alkyl-bromide terminated conjugated moieties,including diketopyrrolopyrrole(DPP),naphthalene diimide(NDI)and perylenediimide(PDI)moieties.We found that these hyperbranched polyelectrolytes possess good water/alcohol solubility and semiconductive property rendering them good candidates for PSCs and photocatalysis.In the PSCs,these hyperbranched polyelectrolytes could lower the work function of metal electrode,facilitate electron collection,and improve the photovoltaic performance.In the photocatalysis,these hyperbranched polyelectrolytes show good water dispersity and provide good interface contact between the polyelectrolytes and water,resulting in efficient photocatalytic hydrogen and oxygen evolution.In Chapter 3,we designed,synthesized and characterized a novel pyridinium-pended conjugated polyelectrolyte(DPTFBr)for the application in photocatalytic hydrogen evolution and organic solar cells.DPTFBr contains pyridinium salts attached to its backbones,which enables a transition from pristine state to a radical state in the presence of amines and illumination via a photo-induced amine doping process.The transition results in apparent shifts in UV-vis absorption spectrum,electrochemical redox potential,as well as electron spin resonance of the resulting polymer.It was found that the unique properties of DPTFBr facilitate its application in photocatalytic hydrogen evolution with a high photocatalytic hydrogen evolution rate of 7.33mmolg-1h-1,which is 63 and 12-folds higher than that of its neutral and oxidized analogues,respectively.Additionally,the excellent interface modification capability of the pyridinium side chains in DPTFBr enables efficient electron transport/collection,thus giving rise to high-performance polymer solar cells with power conversion efficiency over 16%.In Chapter 4,we designed,synthesized and characterized a diketopopypyrrole based conjugated polymer(DTPBr and DTP),which were chemically oxidized and reduced by doping electron donors or acceptors,respectively.It was found that DPP based conjugated polymers show wide-ranging absorption near infrared region which improve the efficiency of polymer solar cells(PSCs)and FETs.Broad absorption leads to increase in conductivity.Among DPP based conducting components,pyridinium linked DPP have demonstrated remarkable potential to improve the materials with sufficient photocatalytic activity and electron mobility... |
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