Design And Synthesis Of Alcohol Soluble Organic Small Molecule Cathode Interface Materials For Organic Photovoltaic Device

Organic photovoltaic cells(OPV) are important subject in the field of solar energy due to their potential advantages oflow-cost, lightweight, easy manufacturing and providing large-scale flexible devices. Todate, many efforts have been made in promoting the development ofroll-to-roll processed organic photovoltaic cells, which indicate a bright future. In order to meet the requirements of commercial application,related materials should be further optimized.Cathode interfacial material(CIM) which is placed between the active layer and cathode becomes a critical element in determining the power conversion efficiency(PCE) and durability of an OPV device. In general, the incorporation of CIMs possess multiple advantages, including(i) adjusting the barrier between the electrodes and the active layer to enhance the ability of extract electron;(ii) improving the electrode charge selectivity, and balancing the charge transfer;(iii) avoiding physical or chemical reactions between the electrodes and active layer;(iv) improving the morphology of the active layer.Organic small-molecule CIMspresent several attractiveadvantages such as high purity and well-defined chemical structures. Thus,this thesis mainly focuses on developing the preparation of high-performance alcohol-soluble organic small-molecule cathode interfacial materialsfor OPVs.(i) Based onversatile cathode interface material Phen-NaDPO, we further optimize the synthesis routes to avoid the utilization of butyllithiumand prepare novel CIMs: C4-Phen, C8-Phen and flu-Phen. Among them, the solution-processed photovoltaicdevice(ITO/PEDOT:PSS/PTB7:PC71BM/CIM/Al) utilizing flu-Phen as the CIM achieved a high PCE of 7.56%.(ii) The cathode interface materials exhibit resistance to weakly polar solvents benefit fortheirapplication in inverted OPVs.In contrast tothe zwitterionsPONN-Z reported before, we report a novel zwitterion(PONQ-Z)with easier synthesis and purification.Inserting PONQ-Z into the OPV device(ITO/ZnO/PONQ-Z/PTB7:PC71BM/MoO3/Al)providedhigher PCE of 8.41% than the pristine ZnO devices.