Simulation And Experimental Study On Performance Of LED Chips Affected By Graphene Transparent Electrode And Carbon Dots

Light-emitting diodes(LEDs)are widely used due to their advantages of small size,long life,and low energy consumption.However,as the requirements for the brightness of the LED become higher and higher,the power of the LED continues to increase.As a result,there are some problems such as LED chip current crowding,excessive junction temperature,and aging of the packaging glue,which seriously affect the LED luminous efficiency and lifetime.Optimizing the transparent electrode of the chip can alleviate the current jam,increase the current injection rate,reduced the junction temperature of the LED chip,thereby prolonging the service life of the LED.Optimizing the phosphor package can enhance the luminous efficiency and increase the use range and the service life of the LED device.However,how to optimize the transparent electrode structure and the phosphor package? First of all,it is necessary to use a simulation to make a preliminary theoretical prediction,and then verify it through experiments.Therefore,this paper used COMSOL Multiphysics multi-physics finite element simulation software,according to the chip current expansion theory,the effects of transparent composite electrodes composed of graphene and different metals on the electrical and thermal properties of GaN-LED are simulated;The COMSOL RF module and TracePro ray tracing software calculated the PL emission spectra of carbon quantum dots(CDs)and the effects of different concentrations of CDs/UV encapsulating compound phosphors on the LED light output performance.The self-made CDs were encapsulated with UV glue and then encapsulated.The experimental simulation of the light output performance was verified.The main results are as follows:1.Graphene/Metal(Gold,Silver,Nickel,Platinum)composite transparent electrodes can effectively alleviate the current crowding of GaN-LED chips(350?m × 350?m).It was found that three-layer graphene and 1nm gold(Au),1.5nm silver(Ag),1.5nm nickel(Ni)and 1.5nm platinum(Pt)were used as a composite transparent electrode compared with graphene alone as a transparent electrode.The junction temperature of the LED chip is reduced by ~12K and its performance is optimal.At the same time,a composite transparent electrode consisting of four metals and graphene was compared,and the graphene/nickel composite transparent electrode had the best LED performance.2.The relationship between PL emission spectra and size of CDs was explored through COMSOL simulations,and 2nm CDs were found to have emission peaks at 585 nm.The best thickness of CDs/UV-glue phosphor on 35 mil × 35 mil LED chip is 2.3mm;10mol/L CDs/UV-glue phosphor is solidified on the LED chip,and the blue LED can excite the phosphor to emit yellow light.Finally get white light.3.Yellow phosphor CDs with a size of about 2nm were prepared by a hydrothermal method.When the CD/UV-glue concentration was 1.2mg/10 mL,the blue LED could also excite the phosphor to emit yellow light.This is in accordance with the TracePro simulation CDs/UV-glue composite phosphor concentration was 10mol/L.According to the PL test,the emission peak of the CDs peaks at 590 nm,which is very close to the theoretical peak at 585 nm.The error is only 1%.The use of software to simulate different metal thin film/graphene transparent electrode and CDs/UV-glue composite phosphor to explore the photoelectric thermal performance of LED has certain reference value and guiding significance.