Fabrication Of Transfer-free Metal Mesh Transparent Electrode For Flexible Polymer Solar Cells

With development of flexible optoelectronic devices,as an indispensable component,transparent electrodes possessing mechanically flexible(upon bending or stretching)is crucial.However,Indium tin oxide(ITO)is most currently used transparent electrode with mechanical brittleness,thereby application in flexible optoelectronic devices is limited.The metal grid transparent electrodes offer characteristics of lower resistivity,low cost,solution processing,better flexiblility and large-scale production of roll-to-roll processes.However,the high thickness,poor adhesion,low uniform conductivity,and high temperature annealing of metal grids are the major barrier in their device performance.Applied in optoelectronic devices,the metal grids need to transfer,semi-embedding,etc,which significantly increases the complexity of the eldctrode material process.It is a great significance to prepare a flexible and ultra-adhesive metal grid transparent electrode by transfer-free process,but there are few studies on transfer-free at present.In this paper,we mainly study the preparation of ultra-adhesive and ultrathin metal grid flexible transparent electrodes(FTEs)by transfer-free method,and applies in flexible polymer solar cells(PSCs).Firstly,super-adhesive and mechanically flexible silver grids FTEs were successfully fabricated by in-situ growth silver film with 70 nm thick and low temperature on ultra-adhesive polydopamine(PDA)coated flexible substrate,and electrospun polymer fibers mask aided acid etching.It exhibited high transmittance(T)of 87.2%and sheeet resistance(R_s)of 22.9?/sq,the R_s standard deviation of 2.02?/sq.The conductivity of Ag grids FETs showed little change after bending,stripping or ultrasonic.Moreve,the corresponding PSCs had power conversion efficiency(PCE)of 6.4%in 1.01 cm~2 effective area.These results show that the transfer-free technology has great potential to improve adhesion and mechanical durability of metal electrodes.Secondly,the electrodes photoelectric and mechanical performance benefit from the improved order and ultrathin of Ag grids,respectively.Therefore,combined with the advantages of previous work,on viscous PDA-coated flexible substrate,we further proposed a simple and green electroless-assisted inkjet printing method to prepare ultrathin(50 nm)Ag grid FTEs with higher R_s(9?/sq)and higher T(89.9%).The corresponding PSCs had a PCE of 10.24%at 1 cm~2 effective area.Moreover,the normalized PCE retained 81%of the original PCE after 1500 bending.The device without encapsulation showed retained original PCE of 83%after exposure 30 days.The ultrathin silver grids prepared by electroless-assisted inkjet printing exhibits excellent durability and operational reliability.In order to avoid the process of removing the polymer mask and substrate pretreatment above,we inkjet printed polymer grids containing amino functional group directly on flexible substrates as a template to achieve in-situ grow metallic copper at low temperature,showing better R_s-T(13.12?/sq-88.2%).By studying the configuration of ink,it was found that two-component solvent ink can obtain a stable ink and control coffee ring effect,so a straight grid can be printed without substrate pretreatment.The transfer-free method can realize the preparation of uniform metallic grids FTEs without pretreatment or posttreatment process.In this paper,the preparation of metal grids transparent electrodes performs a green reaction directly on flexible substrate,which is eco-friendly and cost-effective.The transfer-free methods enable a simple and efficient production of flexible metal electrodes and provides prospect for commercial application.