The Study Of The Relationship Between Metal Electrode And Performance Of Flexible OLED

Flexible organic light-emitting diodes have attracted much attention due to their flexible characteristics.The substrates and electrodes of FOLEDs require good mechanical flexibility.Metal electrodes match the mechanical flexibility of the substrates well because of their good malleability,which are often used as flexible electrodes.In this thesis,Ag and Al are used to study the relationship between metal electrodes and device performance.The specific work is as follows:1.The relationship between the Ag thin metal electrode and the CBP as host was investigated.When NPB was inserted between the Ag electrode and CBP or CBP was replaced by NPB as the hole transport layer in the device structure of Ag/ MoO₃/ CBP/ CBP: Ir?ppy?2?acac?/ TPBi/ Cs₂CO₃/ Al,the turn-on voltage of the devices was reduced from 4.2 V to 3 V or 2.8 V.And the maximum current efficiency was increased from 16.28 cd/A to 43.24 cd/A or 74.33 cd/A,respectively.Moreover,when TCTA used as the exciton blocking layer was introduced between NPB and CBP,the current efficiency was still as high as 62.98 cd/A at the luminance of 20000 cd/m2,which was only reduced by 5.61 cd/A.The Ag electrode has a much rougher surface and mismatched energy level with CBP,which make them could not contact directly.So the hole transport layer of NPB and the exciton blocking layer of TCTA were used to improve the energy matching,thereby improving the efficiency and stability of the device.2.The effect of Ag or Al as the transparent anode on device performance was discussed.When Al was used as the thin metal electrode,the maximum current efficiency of devices based on the structure of CBP/CBP: Ir and TCTA: Ir was 67.3 cd/A and 63.4 cd/A,respectively,indicating that Al electrode was suitable for both device structures.When Ag was used as the thin metal electrode,the maximum current efficiency could reach 84.5 cd/A by rationally designing the device structure.It showed that thin metal Ag was more suitable for the anode in the optimized structure of the flexible device.3.White FOLEDs with bimetallic electrodes were fabricated and studied utilizing the spectral effect of microcavity.By adjusting the proportion of yellow dye doping,a maximum current efficiency?29.35 cd/A?and CIE?0.3452,0.4399?of white FOLEDs were achieved.The maximum current efficiency could reach 26.62 cd/A,CIE?0.346,0.3824?by changing the thickness of the hole transport layer.The results showed that the spectral effect of the microcavity could not only use the thickness to adjust the color of the spectrum,but also play a role in the spectral regulation of the doping concentration.The high efficiency and high purity white FOLEDs could be prepared by using the microcavity effect.