Research On Improving The Luminescent Properties Of Organic Light-emitting Devices

Organic light-emitting devices(O LED)is considered to be a new generation of lighting and flat panel display technology candidate because of their wide viewing angle,light weight,low energy consumption and other advantages.I n nearly 30 years of research,organic light-emitting technology has a rapid development,but the troubles of light emitting efficiency and stability are still very prominent.This paper mainly includes the following three parts:(1)In this work,the effect of buffer layer on the performance of organic light emitting diodes(O LED)was studied by adding m-MTDATA(4,4',4''-Tris(N-3-methylphenyl-N-phenylamino)triphenylamine)as buffer layer between anode and hole transport layer(NPB).The devices of ITO/m-MTDATA(d nm)/NPB(40-d nm)/Alq3(70nm)/LiF(0.5nm)/Al(40nm)?ITO /MoO3(15nm)/NPB(25 nm)/Alq3(70nm)/LiF(0.5nm)/Al(40nm)were prepared.The effects of different m-MTDATA thickness on the performance of OLED were studied by measuring luminance,current density and current efficiency.It is found that the turn-on voltage of the device is reduced from 13 V to 9V when the thickness of the buffer layer is 15 nm,and the maximum brightness of the device is increased from 5900cd/m2 to 16300cd/m2,it is about 2.76 times as much as which of the device without buffer layer.The highest current efficiency has also increased from 1.8cd/A to 3.5cd/A,which is 1.94 times as much as the original device.Then the 15 nm thickness of MoO 3 was inserted as a buffer layer between ITO and NPB in the device.By comparison,we found that the turn-on voltage of the device which insert buffer layer of MoO 3 is reduced to 8V,the maximum brightness is 13320(cd/m2),the maximum current density is 6030.74(A/m2)and the maximum current efficiency is 3.06(cd/A).(2)The DMAC-DPS: m-MTDATA hybrid films with a certain thickness were prepared with different blend ratios.The photoluminescence spectra and quantum efficiency were tested.The results show that when the ratio of two materials is 2:1,the quantum efficiency of the hybrid films reach a maximum value of 32.8%.Therefore,we think that 2:1 is the best ratio of the two compounds.Then organic light emitting diodes were prepared with the DMAC-DPS: m-MTDATA hybrid films with different blending ratios as the light emitting layer.It is found that when the ratio of DMAC-DPS to m-MTDATA is 2:1,the maximum brightness,the maximum current density and the maximum current efficiency were obtained in the O LED device.The optimum ratio is the same with the photoluminescence of the mixed films.(3)The effect of temperature on the emission spectrum of TAPC: BCzVBi hybrid films was studied.The surface morphology,absorption spectra and normalized photoluminescence spectra and photoluminescence spectra of TAPC : BC zVBi hybrid films were analyzed Comparing the absorption characteristics and PL spectra of TAPC,BC zVBi and TAPC : BC zVBi hybrid films,we found that the absorption peak of the hybrid film coincided with the absorption peak of TAPC and the absorption of BC zVBi was inhibited by energy transfer.There are two luminous peaks in the hybrid films.O ne luminous peak coincides with the main peak of BC zVBi,which keeps constant and the other shifts red when the temperature decreases.The luminous intensity of both peaks increased with the decrease of temperature.