Research On Chromatographic Performances Of New Top-emitting WOLED

Top-emitting organic light emitting diode(TOLED)has received wide attention in the industry for its high opening rate,high brightness and high color purity.Top-emitting white organic light emitting diode(TWOLED)has shown great potential in high-performance full-color display technology,flexible display technology,new energy-saving lighting technology and large-area ultra-thin backlight technology,and has attracted much attention once reported.Although the current TWOLED research has been more in-depth,but the stability of the device,efficiency and other performance to be further improved,the manufacturing cost to be further reduced.For this reason,this thesis adopts a color conversion structure with low cost and simple preparation process to realize TWOLED,and starts the research from three aspects:the composite cathode of the device,the blue phosphorescent TOLED,and the effect of the variation of DCJTB concentration in the color conversion layer(CCL)on the optoelectronic performance of the device,as follows.First,the effect of the Al/Ag composite cathode on the performance of TOLED devices was investigated.The best electron injection performance is achieved when the thickness of the composite metal cathode Al/Ag is 0.8 nm/22 nm.The Al film can effectively flatten the spikes on the Ag film to prevent the Ag from breaking through the organic layer and directly connecting with the ITO anode to cause device short circuit.The optical coupling layer Alq₃ can effectively improve the transmittance of the device's translucent cathode,reduce its reflectivity,and improve the device's optical coupling out efficiency.When the thickness of the optical coupling layer Alq₃ is 50 nm,the microcavity effect has the least effect on the device spectrum,the spectral intensity does not change with the observation angle,the maximum brightness of the device can reach7378 cd·m^-2,and the maximum current efficiency of the device reaches 4.51 cd·A^-1.Next,Firpic-based blue TOLED were investigated,carrier equilibrium was achieved by adjusting the thickness of the hole injection layer Mo O₃ and the hole transport layer TAPC to achieve carrier migration equilibrium and the best device efficiency when the thickness of Mo O₃ was 5 nm.The maximum brightness of 7111 cd·m^-2 and the maximum current efficiency of 6.68 cd·A^-1 were obtained when the TAPC thickness was 30 nm.Then,a blue TOLED with dual light-emitting units was designed,and it was found that the structural design with TCTA as the main material of the first light-emitting unit and Tm Py Pb as the main material of the second light-emitting unit is beneficial to the carrier balance of the device,and the exciton complex light-emitting area can be expanded to enhance the device efficiency,and the maximum brightness can reach 12180 cd·m^-2and the maximum current efficiency can reach 9.76 cd·A^-1.Finally,TWOLED implementation of color conversion films based on DCJTB was investigated.The characteristic luminescence spectra and CIE coordinates of the red fluorescent small molecule material DCJTB and the blue phosphorescent material Firpic were investigated,while TWOLED based on different concentrations of DCJTB were prepared,and it was determined that TWOLED near the white light isoenergetic point(0.33,0.33)could be obtained at DCJTB mass fractions of 2.0 wt%-3.0 wt%.CCL with DCJTB mass fractions of 2.0 wt%,2.5 wt%,and 3.0 wt%were combined with high-quality dual-emitting unit blue TOLEDs immediately afterwards.It was found that at a DCJTB mass fraction of 2.5 wt%,a white light emission with weak microcavity effect and stable chromatography was obtained with the maximum current efficiency of 2.45cd·A^-1,a CIE of(0.338,0.337),a CRI of 72,and a shift of only(0.049,0.016)from 0°to60°CIE color coordinates,and when the current density was gradually increased from 1m A·cm^-2 gradually increases to 100 m A·cm^-2,the color coordinate fluctuation is extremely small and only changes by(0.005,0.005).The new top-emitting blue light structure with Ag reflector combined with the new TWOLED microcavity effect realized by CCL is weak,which obviously improves the phenomenon of conventional TWOLED chromatographic drift and shows good color stability.