| Graphene has excellent photoelectric and mechanical properties,and it is widely used as a flexible transparent electrode in optoelectronic devices.As graphene anode is applied in light emitting diodes,intrinsic graphene has high sheet resistance and low work function,which often lead to the device performance degradation.Besides,the hydrophobicity property of graphene also limits its practical application.In this thesis,surface doping method is used to reduce the sheet resistance and increase the work function of graphene.The wettability of poly（3,4-ethylenedioxythiophene）polystyrene sulfonate（PEDOT:PSS）on graphene is improved by modifing with surfactant dopant.The monolayer graphene is used as transparent electrodes of organic light-emitting diodes（OLEDs）,pevroskite quantum dot light-emitting diodes（PQD LEDs）and perovskite nanocrystal light-emitting diodes（PNC LEDs）to conduct a series of studies,which are summarized as below:（1）Graphene electrode was doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane（F4-TCNQ）to reduce the sheet resistance and increase the work function of graphene.The work function of graphene was increased by 0.6 eV,and the sheet resistance was decreased by 250Ω/sq.Green OLEDs with the F4-TCNQ doped graphene anode were fabricated.However,it was difficult to obtain a uniform PEDOT:PSS film on the surface of the hydrophobic F4-TCNQ doped graphene film due to its hydrophilic property.In order to solve this problem,the surfactant Triton X-100 was added into PEDOT:PSS solution,which significantly improved the quality of the PEDOT:PSS film.Finally,the turn-on voltage of the OLEDs based on F4-TCNQ doped graphene was reduced from4.1 to 3.0 V,the maximum brightness was increased from 24940 to 44540 cd/m2,and the current efficiency and luminance efficiency are increased from 54.4 cd/A and 34.1 lm/W to 79.0 cd/A and63.1 lm/W,respectively.（2）MAPbBr3 quantum dots were synthesized successfully and applied in light-emitting diodes.Moreover,the graphene based PQD LEDs was firstly constructed.In order to improve the wettability of PEDOT:PSS on the surface of graphene electrodes,Triton X-100 and DMSO were used to incorporate in PEDOT:PSS solution.This co-doping modification strategy significantly improved the quality and the conductivity of PEDOT:PSS film,resulting in the phase separation of PEDOT:PSS film and the formation of nanofibre PEDOT conductive channels.We analyzed the influence of different doping concentrations on device performance.The current efficiency and external quantum efficiency of the optimal device were 2.12 cd/A and 0.67%respectively,which are 4.4 times and 3.8 times higher than those of the unmodified device.（3）FA0.8Cs0.2PbBr3 nanocrystals were synthesized successfully and applied in graphene based light-emitting diodes.In order to improve the performance of the device,we use the Triton X-100and DMSO modified PEDOT:PSS as the hole transport layer.Finally,the first PNC LED based on graphene electrode was constructed.The current efficiency and external quantum efficiency of the device are 11.37 cd/A and 2.58%,which are 7.4 times and 7.3 times higher than those of the device without modification.In this thesis,the overall performance of graphene-based OLEDs,PQD LEDs,and PNC LEDs were improved by doping graphene and modifying PEDOT:PSS.We applied graphene electrodes in PQD and PNC LEDs for the first time,which provided some guidelines for the future research of flexible PQD and PNC LEDs based on graphene electrode. |
