Crosslinkable Conjugated Polymers:Design,Synthsis And Application In Polymer Solar Cells

Polymer solar cells(PSCs)have attracted considerable attention due to their advantages of light weight,flexibility and low-cost solution processing techniques.Inverted polymer solar cells(IPSCs)with indium tin oxide(ITO)as the electron collection electrode showed higher device stability than the traditional devices with low work function metal as cathode.The modification of metal/metal oxide electrode is of great importance to the performance of inverted organic optoelectronic devices.Cross-linked films provide a good chance to modify the metal/metal oxide electrode and enable the fabrication of high-performance multi-layer organic optoelectronic devices due to its superior ability to resist solvent erosion.However,most of the reported methods to prepare cross-linked films are suffering from the harsh processing conditions such as high-temperature thermal treatment or long-time UV radiation.The requirement of fast and efficiently crosslinking process is necessary to be solved.Here,we use two novel cross-linking mechanism to develop two kinds of cross-linking films,which can work as the interlayer with highly solvent resistance and cross-linking processing can be realized under mild conditions.The corresponding thesis is constructed as follows.In the second chapter,we develop a novel fast cross-linking method of PFN-V interlayer by UV-curing within 5s based on the “click” chemistry of alkyene end-groups of PFN-V side chains and addition of 1,8-octanedithiol.The cross-linking films show a good solvent resistance property and can act as effective cathode interlayer to modify the indium tin oxide electrode.The surface energy of PFN-V is quite comparable to that of PC71 BM,which is favorable for the formation of vertical phase separation in the bulk heterojunction film.Based on the resulting PFN-V as cathode interlayer,the fabricated polymer solar cells with the inverted structure ITO/PFN-V/PTB7-Th: PC71BM/MoO3/Al show a remarkable enhancement of power conversion efficiency to 9.18%.In the third chapter,we develop novel robust cross-linked thin films which are prepared from an epoxy-functionalized conjugated polymer(PFEX)and an amine-based small molecule(TAA).The cross-linking processing can be realized under mild heating due to the highly-efficient amine-epoxide reaction,and the resulted cross-linked films show good solvent resistibility.Moreover,the cross-linked films showed large tolerance with the composition of PFEX and TAA,which provides opportunity to modify the metal/metal oxide electrodes in a wide range using the cross-linked films.The modified indium tin oxide(ITO)using the cross-linked films show much lowered work function and hydrophobic propertythan the pristine ITO,which indicates great potential application in inverted organic optoelectronic devices.Inverted polymer solar cells(IPSCs)using the modified ITO shows remarkable enhanced power conversion efficiency(9.4%)than those with pristine ITO(6.8%).Furthermore,we found that the performance of the IPSCs is positively correlated with the amine density in the cross-linked film.