Enhanced Efficiency Of The Top-emitting Organic Light-emitting Device With Corrugated Microstructure

As a new kind of disply device organic light-emitting device(OLED), eespecially the top-emitting organic electroluminescent device has a lot of advantages in applications, because it has higher ratios of pixels. Although enhancing the efficiency of the OLED is concerned by most reseacher. To achieve high effiiciency in OLED the first is the efficiency of the radiative exciton be formed . The second is the efficiency of the usful radiation from the decay of the excition. The thied is the efficiency of the light getting out of the OLED. Typically more than 50% of the light praduced by excition decay never leave the device, being trapped in the form of waveguide modes and ultimately lost to absorption. The efficiency of the OLED is biggly affected.At the same time in the OLED devices, metal electrodes are commonly used. Much less well appreciated is the loss of efficiency that arises due to quenching of excitions by surface plasmon(SP)modes. Surface plasmon (SPs) are surface charge density oscillations that existe at metal/dielectric interface. Further, we want to solve the prblom of SP resonance absorption. We show experimentally that through the use of appropriate Bragg scatterring periodic microstructure. We want to reallize surface plasmon cross coupling to recover the power lost to surface plasmon modes. As a result more light will luminescence out of the semi-transparent metal electrode, and enhance the efficiency of the top-emitting organic electroluminescent device.We use UV laser emitted from chusheQuanta-Ray-150 nanosecond laser as interference light soure. We set up the path of two-beam interference and the path of three-beam interference on the flotation platform. We use spin-coating method fabricated NOA-63 and SU-8 photoresist film with the thickness of 100nm on sillicon substrates. We use maskless lithography single-exposure and double exposure technology fabrecated one-dimensional and two-dimensional grating microstructure with smooth surface and uniform morphology.We fabricated the top emission OLED with grating microstructure, and realize the cross coupling of surface plasmon at the interface between Ag and organic film. We make the top-emission devices with the structure of Si/grating(500nm)/Ag(80- nm)/MoO3(4nm)/NPB(55nm)/Alq3(55nm)/LiF(1nm)/Al(2nm)/Ag(50nm) and Si/ Ag(80nm)/MoO3(4nm)/NPB(55nm)/Alq3(55nm)/LiF(1nm)/Al(2nm)/Ag(50nm). The efficiency of former device is an average of 38.77 percent higher than the latter one. Maximum brightness of flat panel device is 13000cd/m2, and grating device with the maximum brightness is up to 15000cd/m2. The result indicate that surface plasmon cross coupling recover the power, and enhance the efficiency of the top-emission OLED.We deposit 200nm small moleculer materrial NPB onto the semitransparent cathode in order to enhance light output. So we fabricated the devices with the structures of Si/Ag(70nm)/MoO3(5nm)/NPB(70nm)/Alq3:DCJTB(8%)(50nm)/Alq3 (25nm)/LiF(1nm)/Ca(2nm)/Ag(20nm)/NPB(200nm) and Si/Ag(70nm)/MoO3(5nm)/ NPB(70nm)/Alq3:DCJTB(8%)(50nm)/Alq3(25nm)/LiF(1nm)/Ca(2nm)/Ag(20nm). From the electrical/optical characteristic curve we get that light output layer enhance the efficiency of the device by 39.44%.We introduce grating microstructure into the device with light output layer. When the two side of the Ag film are the material with familiar dielectric constants, the efficiency of the light output will be increase to the maximum extent. So we fabracated the devices with the structure of Si/grating(370nm)/Ag(70nm)/MoO3/ (5nm)/NPB(70nm)/Alq3:DCJTB(8%)(50nm)/Alq3(25nm)/LiF(1nm)/Ca(2nm)/Ag(40nm)/NPB(200nm) and Si/Ag(70nm)/MoO3(5nm)/NPB(70nm)/Alq3:DCJTB(8%) (50nm)/Alq3(25nm)/LiF(1nm)/Ca(2nm)/Ag(40nm)/NPB(200nm). The efficiency of the device with grating structure is 79% higher than the plate device in an average.