Strategies For Improving Short Circuit Current Of Organic Solar Cells Based On Perylene Diimide

In recent years,Organic Solar Cells（OSCs）have achieved a dramatic improvement in power conversion efficiency through the material design and device engineering.The development of novel donor materials and non-fullerene acceptor is the main methods to improve the performance of OSCs.Among many non-fullerene acceptors,perylene diimide（PDI）has been widely used in the field of OSCs due to its high electron mobility,low cost,good optical and thermal stability.Considering that important research progress has been made in the synthesis of PDIs materials,the exploration of novel device engineering strategies is of great significance to further improve the performance of PDIs based devices.Generally speaking,Short Circuit Current(J_SC)is an important parameter to measure the performance of OSCs.Its value is not only affected by the inherent optoelectronic properties of the material,but can also be regulated by device optimization methods such as additives and solvent vapor annealing.Therefore,this thesis studies the effects of additives and solvent vapor annealing on the J_SC of PDI-based OSCs.The specific content and results are as follows:（1）The additive poly-4-trifluoromethylstyrene（PTFS）was synthesized,and polystyrene（PS）was used as the control additive to study the effect of different additives on the J_SC of polymer-donor/PDIs acceptor based OSCs.The results showed that 4 wt%PTFS addition based device obtain a J_SCof 14.40 m A cm^-2,which was significantly higher than that of the device without addition treatment(J_SC was 11.92m A cm^-2)and the device treated with 4 wt%PS addition(J_SCwas 11.59 m A cm^-2).These results are mainly attributed to the the additive PTFS can improve the light absorption of the active layer and promote the formation of a good phase separation morphology between the donor and the acceptor.In addition,PTFS as an additive can not only enhance the thermal stability of the device,but also promote the J_SC value in other polymer donor/small molecular acceptor systems.（2）Additives significantly improved the J_SCof polymer donor/PDIs acceptor based OSCs.However,the large batch-to-batch performance variation of polymers hinders application and promotion of such devices.In contrast,small molecules have gradually become a hot spot in the field of OSCs research due to their well-defined structure,high purity,small batch-to-batch variation,and good tunability of energy levels and absorption.Therefore,the small molecule donor/PDIs acceptor OSCs was fabricated and investigated the effect of different solvent annealing treatments on the J_SC of all-small molecule devices.The results show that the J_SC can be improved from4.28 m A cm^-2 to 9.50 m A cm^-2with the solvent carbon disulfide（CS₂）treated.The reason for the substantial increase in J_SCis that the CS₂ solvent vapor annealing treatment can induce stronger aggregation and intermolecular interactions,forming an appropriate phase separation,thereby enabling the device to obtain higher carrier mobility.