The Study On Carrier Transport And Consolidation Morphology In Organic Solar Cells

In recent years,organic/polymer thin film solar cells have attracted more and more attention because of their advantages such as low cost,light weight,simple fabrication process and flexibility.In this thesis,the double electron transport layer is introduced into organic solar cells to improve the collection of electronic carriers,and the performance of solar cells is improved by adjusting the aggregation morphology of the active layer.The main contents and conclusions of this thesis are as follows:1.In order to improve the mobility and efficiency of solar cell devices,a small molecule ITIC with good planarity and high electron mobility is introduced as the electron transport layer,and a double electron transport layer is constructed to improve the electron carrier transport in organic solar cells.The ITIC electron transport layer was prepared on the ZnO layer by spin coating method.In order to avoid the interlayer being destroyed by solvent,we used the process of spontaneous spreading(SS)formation to fabricate devices.This method can easily avoid the destruction of ITIC layer by first forming film on the surface of water and then adsorbing it on the substrate by electrostatic force.Compared with spin coating process,the method of fishing film does not need to be processed in nitrogen atmosphere,but can be directly processed in air.The results show that the electronic mobility of devices can be improved by constructing ITIC/ZnO double electron transport layer,which promotes exciton separation.The defects on the ZnO layer can be repaired by introducing ITIC electron transport layer,and the morphology of devices can be optimized.Compared with devices without interlayer,it achieves higher photoelectric conversion efficiency.2.Material is an important part of organic thin film solar cells.For polymers,the molecular weight of conjugated polymers is closely related to the morphology of the active layer,and by changing the molecular weight of the polymer,the aggregation morphology of the active layer can be regulated and the performance of organic photovoltaic devices can be improved.PBDB-T,as a star polymer,is widely used as donor material in organic solar cells.For this reason,we synthesized PBDB-T with different molecular weights,and used different solvents and processing conditions to control the morphology of its active layer to obtain the best device performance.Result: In chlorobenzene(CB)solution,with the increase of molecular weight,the aggregation degree of active layer is increasing.The suitable aggregation morphology appears in the morphology of active layer with low molecular weight of polymer.The efficiency of device increases first and then decreases.In o-dichlorobenzene(o-DCB)solution,with the increase of molecular weight,the aggregation degree of active layer also increases from small to large.The appropriate aggregation morphology appears in the active layer morphology with high molecular weight,and the device efficiency increases with the increase of polymer molecular weight.The research results in this thesis provide important reference for the fabrication and optimization of organic solar cells.