Study On The Interface Modification And Performance Of Organic Solar Cells

Organic solar cells(OSCs)have the advatages in low-cost,light-weight,good response to weak illumination and good flexibility,and belongs to the one of hot fields in photovoltains due to their application potentials in such as mobile exctronic devices,photovoltaic buildings and military power supply.This dissertation aims to develop the efficient electron-and hole-transporting interfaces for the OSCs based on p-type conjugated polymer electron donors and n-type small molecule electron acceptors for improving device performances.For this purpose,the molecular design,synthesis and working principles of novel interfacial materials are investigated in the dissertation.The main research activities and conclusions in this dissertation are summarized as follows:(1)Three kinds of non-conjugated organic small molecule electrolytes(abbrev.OAS,SAS and SOAS),which contain amino cations,sulfonate anions and different core atoms,are designed and synthesized.They are used as electron-transporting interfacial materials in the OSCs based on PBDB-T:IT-M photoactive layer,resulting in the best power conversion efficiency(PCE)of 11.30%,much higher than the counterpart devices with methanol treatment and Ca as the interfacial material.It is found that the introduction of the non-conjugated organic small molecule electrolyte interface in between photoactive layer and Al electrode not only reduces the workfunction(WF)of Al electrode and forms interfacial dioples to accerlerate the effective charge transport,but also reduces effectively the bimolecular recombination at photoactive layer/Al electrode interface,both of which act to improve the device performance.(2)The Ag NWs/PEDOT:PSS composite hole-transporting material is prepared by doping PEDOT:PSS with Ag nanowires(Ag NWs).Results show that the Ag NWs/PEDOT:PSS composite has a higher conductivity and a lower WF than pristine PEDOT:PSS,but their light transmittance in the spectral range of 300-900 nm and film-forming property are comparable to each other.In the solar cells based on PBDB-T:IT-M and PBDB-T-2Cl:IT-4F photoactive layers,it is found that the Ag NWs/PEDOT:PSS interface is remarkably effective than pristine PEDOT:PSS one,because the former interface increases the interfacial dissociation efficiency of excitons and the transporting efficiency of charge carriers and reduces the interfacial recombination of charge carriers;the best efficiency of PCE=13.53%is achieved in the solar cells based on the Ag NWs(5%)/PEDOT:PSS interface with an optimal composition and the PBDB-T-2Cl:IT-4F photoactive layer.(3)Novel n-SnO2/InP/ZnS QDs electron-transporting layer(n-SnO2/InP/ZnS QDs ETL)is prepared by modifying n-SnO2 ETL with InP/ZnS quantum dots(QDs)as electron-transporting interfacial material.In the inverted OSCs based on PM6:Y6 photoactive layer,it is found that the use of n-SnO2/InP/ZnS QDs ETL improves the morphology of the followed photoactive layer;and that InP/ZnS QDs does not affect the photon harvesting and the exciton dissociation in the solar cell but passivate the surface defects of n-SnO2 ETL,resulting in the significantly improved charge extracting efficiency at photactive layer/ETL interface and charge collection efficiency at electode,as well as the decreased monomolecular recombination caused by the defect-trapped charge carriers.Upon the synergistic effects of the improved photoactive layer morphology and interfacial charge behaviors,the inverted OSCs with n-SnO2/InP/ZnS QDs ETL exhibits a remarkably improved Voc,FF and stability,and further an efficiency of PCE=15.22%.