| Conjugated polymer has found its wide application in solar cells,field-effect transistors and electronic devices due to its distinctive characteristic of flexibility,good structure tenability,wide sources of raw materials.Optimization of the properties of conjugated polymers,which plays a critical role to achieve good device performance,mainly focused on the backbone manipulation and side chain modification.In this dissertation,we present a novel strategy to improve the aggregation and charge transport property of polymer through functionalization of side chain terminal.Furthermore,the charge mobility of conjugated polymer is relatively low and the combination of conjugated polymer with the carbon material may yield the increased electrical conductivity.Modification of the polymer side chain may improve the miscibility of the polymer with carbone material.The detailed works are listed as follows.1)A composite of conjugated polymer/graphene oxide(GO)has been synthesized for the application in the anode buffer layer of polymer solar cell.However,the inferior compatibility of the conjugated polymer with graphene oxide may lead to serious phase separation and bad interface contact,and consequently prevent the formation of interpenetrating network for charge carrier.To enhance the miscibility of polymer with GO,the pyrene has been introduced to the side chain terminal and two new conjugated polymers PPOC and PPOCBDT have been synthesized with the main chain constructed with carbazole-carbazole and carbazole-benzodithiophene,respectively.Blending GO with the synthesized polymer gave rise to inferior film morphology with obvious phase separation.So the anone buffer layer has been fabricated adopting trilayer structure of GO/polymer/GO for the application in the inverted polymer solar cell.Results indicated that the anode buffer layer can significantly increase the device efficiency compared to the device without the hole transporting layer.And the device with buffer layer of GO/PPOCBDT/GO showed higher power conversion efficiency compared to GO/PPOC/GO,probably due to the better backbone planarity of PPOCBDT.In addition,the effect of GO film thickness on the device performance was studied in details.2)A series of carbazole-diketopyrrolopyrrole based conjugated polymers PCDPP,PPOCDPP and PCCDPP with different side chains have been designed and synthesized.For PPOCDPP and PCCDPP,pyrene and carbazole unit was incorporated to the terminal of alkyl side chain,respectively.Thermal properties,crystallinities,UV-vis absorptions,electrochemical properties as well as charge transport properties of the polymers were investigated in details.Results showed that incorporation of the fused aromatic rings in the side chain terminals not only changed the absorption and electrochemical properties,but also affected the charge transport properties.The pyrene and carbazole group in the side chain terminal significantly promoted the aggregation of polymer chains,which would provide short-range order for improved charge carrier mobility.Compared to the hole mobility(0.019 cm2V-1s-1)for polymer PCDPP with the alky chains,increased hole mobility of 0.081 cm2V-1s-1 and 0.052 cm2V-1s-1 was achieved for polymer PPOCDPP and PCCDPPP,respectively.3)Two donor-acceptor conjugated polymer PCBT and PPOCBT has been syntheized based on the benzothiadiazole as the accept and carbazole as a donor.UV-vis absorptions,thermal properties,electrochemical properties and photovoltaic properties of the polymers have been investigated in details.The results indicated that polymer PPOCBT possessing the pyrene functionalized side chain exhibited the similar properties to polymer PCBT.The limited influence of the pyrene may be ascribed to the weak intermolecular charge transfer and disordered molecular aggregation,leading to the absence of the charge transport junctions induced by the pyrene group. |
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