Synthesis And Applications Of Functionalized Graphene Quantum Dots

Graphene quantum dots(GQDs)are 0D member in the carbon material family.They have high conductivity,high light transmittance,optical stability,small size and adjustability.Polymer solar cells(PSCs)have received extensive attention due to their advantages such as flexibility,solution processability,light weight and low cost,and their performance has been rapidly improved.The improvement of the intelayer material is an important reason for the improved performance of PSCs.As the interlayer material of PSCs,GQDs have the characteristics of low cost,solution processing,reproducible performance and stability,which are of great significance for the practical application of PSCs.However,as the anode interlayer(AIL)of PSCs,GQDs have a smaller work function after modification of the electrode,which is not conducive to forming Ohmic contact with the active layer,and a large energy level barrier results in lower PSCs efficiency,which limits further applications in PSCs.Therefore,this paper has carried out related work on improving the work function of GQDs modified electrode,and its specific contents are as follows:1.GQDs with good water solubility and rich oxygen functional groups were synthesized by electrochemical method.Using the redox reaction,the stoichiometric ratio of GQDs to(?,?,?,2,3,5,6-heptafluoro-o-tolyl)hydrazine was controlled to prepare four F-GQDs with different fluorine contents.The composition,chemical state of the four F-GQDs and the relationship between the work function of the F-GQDs modified electrode and the fluorine content were systematically studied.PBDB-T: IT-M PSCs were prepared with F-GQDs as AIL.The results show that F-GQDs are easy to disperse in strong polar solvents and can be processed in solution,and the electrode modified with F-GQDs with higher fluorine content has a higher work function.The maximum efficiency of PSCs based on F-GQDs AIL is 9.4%,which is 51.3% higher than the efficiency of GQDs-based devices.The improvement in efficiency is because the work function of the F-GQDs modified electrode is aligned with the energy level of the active layer,and the smaller interface barrier facilitates the dissociation and collection of carriers.Therefore,F-GQDs is an efficient AIL material for PSCs,and adjusting the fluorine content of F-GQDs is an effective method to adjust the electrode work function.2.In order to further improve the anode work function of PSCs,F-GQDs,Cl-GQDs,Br-GQDs and I-GQDs(collectively X-GQDs).UPS analysis shows that the work function of X-GQDs modified electrode will increase with the increase of halogen electronegativity.As the AIL,X-GQDs are used in PSCs with an active layer of PM6: Y6,and the device efficiency can reach more than 11.0%.The hydrophobicity and thermal stability of X-GQDs AIL make the stability of PSCs in air superior to devices based on GQDs.Therefore,X-GQDs are a new class of graphene quantum dot materials with higher electrode work function,which can realize the preparation of PSCs with high stability,solution processing and high efficiency.