Synthesis And Photovoltaic Properties Of Cathode Interface Materials For Organic Solar Cells Based On Porphyrin

In recent years,organic photovoltaics(OPVs)have attracted much attention because of their advantages for solution processability,light weight,low cost and flexible.The performance and stability of OPVs depend not only on the active layer materials,but also the interface materials.Porphyrins are widely used in OPVs because of their large π-conjugated systems and their properties can be tuned easily via synthetic modifications of the periphery.A variety of porphyrin-based OPVs donor materials have been reported,but porphyrin interface materials are few.The work of this thesis is to rationally control the structure of porphyrin,and synthesize the interface materials to enhance the photovoltaic properties of the OPVs.In the second chapter,we designed and synthesized a water/alcohol soluble conjugated porphyrin small molecule FNEZnP-OE,in which two amino-functionalized fluorene 9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorenes are linked to a porphyrin core substituted with two polar 3,4-bis-[2-(2-methoxy-ethoxy)-ethoxy]-phenyls by ethynylene linkages,as a cathode interfacial material(CIM)for bulk heterojuction organic solar cells.The PTB7/PC71BM– and PTB7-Th/PC71BM–based devices with FNEZnP-OE as the CIM exhibit power conversion efficiencies(PCEs)of 8.52% and 9.16%,respectively,which are increased by 47% and 41% compared to the devices with no CIM(5.78% and 6.50%),respectively.Most significantly,these PCEs are increased by 13.6% and 8%,respectively,than those with widely used polymer CIM PFN.The outstanding performance of FNEZnP-OE CIM is contributed by not only the polar groups of 9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorenes and 3,4-bis-[2-(2-methoxy-ethoxy)-ethoxy]-phenyls but also the porphyrin-relating π-conjugated backbone of FNEZnP-OE induced by the ethynylene linkages,demonstrating that functionalized porphyrins are very promising interfacial materials.In the third chapter,we synthesized a series of porphyrin-based cathode interfacial materials with the same conjugate structure by side chain modifications on porphyrin.Then systematically investigation was conducted on their optical,electrical and photovoltaic properties.In this chapter we focused on the photovoltaic properties of BrFNEZnP-TC16 and SO3FNEZnP-TC16,and the experiment result showed that the PTB7/PC71BM-based device with BrFNEZnP-TC16 as the CIM exhibit a PCE of 9.07%,respectively,which are increased by 8.1% compared to the device with SO3FNEZnP-TC16 as the CIM(8.39%),respectively.Therefore,it is a good way to effectively improve the photovoltaic properties by the reasonable adjustment of the polar side chains of molecules.