Cathode Interface Modification Of Organic Solar Cell Based On PM6: Y6 System

Facing the increasingly tense energy problem,developing green solar energy is one of the important ways to solve it.Solar cells can convert solar energy into electric energy through photoelectric conversion,which can greatly alleviate the energy problem and has achieved rapid development in recent decades.Among solar cells,organic solar cells have attracted extensive attention from researchers at home and abroad for their characteristics of being easy to prepare,light weight,low cost and being able to be used in the preparation of large-area flexible devices.In recent years,new living organic active layer materials have been reported constantly,in which the photoelectric conversion efficiency of single organic solar cell has reached 18%,and that of three organic solar cell has exceeded 20%.In the positive structure devices,although the photoelectric conversion efficiency of the devices has reached the standard of commercialization,the cathode interface layer used now can not effectively prevent cathode ions from penetrating into the active layer and the device has strict requirements on the thickness of the cathode interface layer,which is the main problem to be solved in the industrialization.In this paper,from the perspective of cathode interface modification based on alignment PM6:Y6 system,we try to solve the stability of organic solar cells and cathode interface thickness sensitivity problems,while improving the photoelectric conversion efficiency of devices.In the second chapter,two alcohol-soluble electron transport layers PFN-Br and PDINO,were compared with PM6: Y6 as the active layer.In terms of chemical structure,the polymer material PFN-Br has the advantages of easy purification,monodispersity,good structure,no end-group contaminants and better batch reproducibility compared with the small molecule material PDINO.In terms of photoelectric performance,the film roughness of PFN-Br device is smoother,the interface contact is better,the interface resistance is smaller,so the FF is higher.However,PDINO-based devices can absorb more photons and produce more excitons.At the same time,PDINO has better exciton dissociation and charge extraction ability,and better electron mobility.Finally,the photoelectric conversion efficiency(PCE)of PFN-Br(15.40%)is lower than that of PDINO(15.43%).In the third chapter,we used PM6: Y6 as the active layer and introduced a new electron transport layer Li F to prepare Li F/PFN-Br and Li F/ PDINO double electron transport layer organic solar cells.The two-layer cathode interface containing Li F can effectively reduce the work function of the BHJ layer,make the energy level arrangement more favorable,optimize the contact between the active layer and the electron transport layer,and enhance the electron transfer and extraction process.At the same time,LIF optimizes the light intensity distribution inside the device,which enables the device to obtain a higher current density.For Li F/ PFN-Br and Li F/ Pdino devices,the PCE is 16.4% and 16.0%,respectively,while the base device is15.4% and 15.4%,respectively.In addition,LIF can effectively reduce photodegradation,prevent water and oxygen from entering the device,improve the stability of the device,and the device PCE remains 70% of the initial value within 30 days.In the fourth chapter,in order to better apply in the industrialization,we used PM6: Y6 as the active layer,and mixed Alq3 into the polymer electron transport layer material PFN-Br to prepare the thickness insensitive electron transport layer device.It is found that when the ratio of PFN-Br to Alq3 is 1:0.1,the efficiency of the device is the highest.When the thickness of the optimized electron transport layer increases from 5nm to 20 nm,the PCE of the device can be maintained at 15.3%-15.7%.The addition of Alq3 enhances the conductivity of the electron transport layer,and the FF of the battery device increases most obviously.The contact resistance between the active layer and the electron transport layer is less,and the electron mobility and electron extraction are both enhanced.At the same time,the electron transport layer of the optimized device has better hydrophobicity,which reduces the corrosion of the device by water,thus improving the stability of the device.