Study On The Surface Plasmon Enhanced Photoelectric Properties Of Organic Light Emitting Diodes

Organic light-emitting diodes?OLEDs?has attracted wide attention due to its self-luminescence,ultra-light,ultra-thin,low power consumption,flexibility and other advantages.Localized surface plasmon resonance?LSPR?of Au nanoparticles?Au NPs?can coupled with excitons and enhance the spontaneous emission rate of excitons effectively,thus improving the performance of OLED.Au nanoparticles?Au NPs?is the local surface plasmon resonance?LSPR?,which could promote light emission effectively through enhanced spontaneous emission rate and thus improve the performance of the OLEDs.Graphene oxide?GO?has been widely used in optoelectronic devices due to its unique physical and electronic properties such as large surface area,high intrinsic mobility and high optical transmittance.This paper focuses on the LSPR effect of Au nanoparticles and the application of GO in organic light emitting diodes.The main work is summarized as follows:?1?The corresponding relationship between the size and morphology of Au nanoparticles and the absorption spectrum are studied,and the LSPR effect is used to improve the photoelectric performance of OLED devices.The diameter of Au nanoparticles is 20 nm,and the absorption spectrum of Au nanoparticles is near 520 nm,which is highly matched with the PL spectrum of the basic device.The anode interface is modified by using Au nanoparticles with different concentration gradients as a hole injection layer.The device structure is ITO/Au NPs/NPB/Alq₃/LiF/Al.Compared with the reference device,when the concentration of Au NPs is 10%,the maximum brightness increases from 2380 cd/m² to 3050 cd/m²,with an enhancement of nearly28.2%.The current efficiency and the maximum external quantum efficiency are increased by 28.6%and 26.4%respectively.?2?The effect of GO hole injection layer on the photoelectric properties of OLED devices are studied.By adjusting GO concentration to change its thickness,the device structure is ITO/GO/NPB/Alq₃/LiF/Al.When GO concentration is 0.5mg/ml,the optoelectronic performance of the device is improved to the best value.The open voltage of OLED device decreases from 3.2 V to 3.0 V,the maximum current efficiency increases to 2.63%,the external quantum efficiency increases to 0.62%,and the maximum luminance increases by 16.8%.On the one hand,according to band engineering,the introduction of GO makes the energy level step between ITO and Alq₃form,which can effectively reduce the energy barrier and improve the hole injection efficiency and luminescent efficiency;on the other hand,the high barrier of GO will hinder the transmission of electrons from Al cathode to ITO and act as an effective electronic barrier layer,thus reducing the electron-hole recombination rate and improving the external quantum efficiency.?3?The effect of GO/Au NPs complex on the photoelectric properties of OLED devices is studied.The device structure is ITO/GO/Au NPs/NPB/Alq₃/LiF/Al.When the concentration of GO/Au NPs is 10%,the maximum brightness of OLED reaches3520 cd/m²,the maximum current efficiency and the external quantum efficiency are3.55 cd/A and 0.77%,respectively,which are increased by 49.2%and 45.3%.On the one hand,introducing Au NPs into Alq₃ can effectively utilize LSPR effect to enhance emission intensity;on the other hand,GO can optimize the energy level structure of the device,and balance the electron and hole injection by blocking the electron from the luminescent layer to ITO and improving the hole injection efficiency,thus further improving the device performance of OLED.