Preparation And Application Of Small Amino-containing Molecules Doped PEDOT:PSS

The hole transport material can effectively modify the electrode,reduce the energy barrier of anode,thereby improving the power conversion efficiency and the stability of the solar cell.The water-dispersible doped radical polymer PEDOT:PSS-4083,as one of the most widely used hole transport materials today,has the advantages of good film formation,high transmittance,and easy processing.However,several key factors have also restricted the development of PEDOT:PSS.A large number of insulating PSS macromolecules are contained in PEDOT:PSS,and there are many sulfonic acid groups that are not doped with PEDOT,resulting in a single work function,relatively low electrical conductivity and poor electrical uniformity.PEDOT:PSS-DA was prepared by directly mixing a trace of dopamine hydrochloride into PEDOT:PSS solution from the angle of sulfonic acid group.Through a series of characterization methods including nuclear magnetic resonance and electron paramagnetic resonance,it was confirmed that the amino group in dopamine hydrochloride could ion exchange with the sulfonic acid group in PSS.In addition,the catechol group in dopamine is easy to form semiquinone radical,which is conducive to the intramolecular charge transfer between the main chain of PEDOT and the semi-quinone radical,contributing to the improvement of work function and electrical conductivity.PEDOT:PSS-DA also shows good electrochemical stability.In PM6:Y6 system,PEDOT:PSS-DA was used as the hole transport material and the power conversion efficiency of 16.55% was obtained,which was significantly higher than that of unmodified PEDOT:PSS.More importantly,the current density/fill factor and power conversion efficiency of the device are significantly improved in other donor/acceptor systems.In order to further compare the influence of the number of hydroxyl groups on doping and verify the effectiveness of the doping of amino groups,we introduced 4-hydroxyphenylethylamine and phenylethylamine hydrochloride doping PEDOT:PSS to prepare PEDOT:PSS-TA and PEDOT:PSS-PA respectively.Compared with the pristine PEDOT:PSS,the work function and conductivity of the three kinds of HTM doped by phenyethylamine derivatives were all improved,and the surface properties were all changed.The improvement range of the conductivity was increased with the increase of the number of hydroxyl groups,while the work function value was decreased.The devices based on the three doped HTMs have achieved their best power conversion efficiency in different systems and are all higher than the pristine PEDOT:PSS-based devices.PEDOT:PSS-TA achieves the best PCE of 17.10% in PM6:Y6 system.PEDOT:PSS-DA obtained the best PCE of 14.17% in PM6:ITC-2Cl system.PEDOT:PSS-PA obtained the best PCE of 9.55% in PM6:PIDTC-T system.In this paper,we provide a simple scheme to modify PEDOT:PSS using small amino molecules.In view of the idle sulfonate base group in PEDOT:PSS,the use of small molecules containing amino group doping,can simultaneously regulate the conductivity,work function,surface properties of PEDOT:PSS,and then effectively improve the efficiency of organic solar cells.This work also revealed that different active layer systems are adapted to different types of hole transport materials.