Fabrication And Research Of Organic Light-emitting Devices

Organic light-emitting diodes (OLED) have become a shining star in theelectronic display field since the end of the 1980s. This technology exhibits brightprospect in photoelectricity field due to its advantages of low DC drive voltage,active luminescence, excellent hue saturation, wide visual angle, etc. Nowadays,small-area OLED have been commercially produced in the area of mobile meters,screens of mobile phones and digital cameras, etc. For OLED, tricolor deviceshave been coming into industrial phase, and white OLED by mixing tricolor lighthave been a very hot studying direction in international. Recently, thecombination of yellow and sky blue light to realize white light emission wasapplied in white-light OLED fabrication, hence, yellow-light OLED has gainedbroad attention. Adopting novel structure of devices, choosing right matchingenergy levels, balancing carriers of OLED, enhancing luminance of OLED andimproving luminous efficiency of OLED have been difficult problems whichOLED developers faced all along. We study a kind of novel yellow organic light-emitting device, whosestructure is double quantum wells and dopant is Rhodamine B for the first time.Alq3 as potential barrier and Alq₃: RhB as potential well of quantum-well, thedevice was fabricated. The device structure: ITO/CuPc(6nm)/NPB(20nm)/Alq₃(3nm)/Alq₃: Rhodamine B (3nm)/Alq₃(3nm)/Alq₃: Rhodamine B (3nm)/Alq₃(20nm)/Liq(5nm)/Al(30nm). When imposed driving voltage on OLED, thedevice emit yellow light successfully. With the detailed investigation of electro-luminescence of the novel organic yellow-light-emitting device, we found thatdoping concentration of Rhodamine B (RhB) had a very important influence onluminance and efficiency of the OLED. When doping concentration of RhB islow, we can find that there is low energy transmission efficiency from Alq₃ toRhB. When doping concentration of RhB is high, severe concentration quenchingeffect would be induced and thus luminescence efficiency decreased. Whendoping concentration of RhB is 1.5wt％, the organic yellow-light-emitting devicewas obtained with the maximum current efficiency of 1.526cd/A and themaximum luminance of 1309 cd/m².The paper report an organic light-emitting device with a kind of newelectroluminescent material-Zr(OPh)₂q₂as emitting layer. The device structure:ITO/CuPc/Zr(OPh)₂q₂/Al. After testing and analyzing, we get the optimalemitting layer's thickness is 30nm, and the biggest luminance is 60 cd/m².Changing the common structure to double quantum wells structure, we get thedevice structure: ITO/CuPc(6nm)/NPB(20nm)/Alq₃(3nm)/Zr(OPh)₂q₂(3nm) /Alq₃(3nm)/Zr(OPh)₂q₂(3nm)/Alq₃(20nm)/Liq(0.5nm)/Al(30nm). Because of thepotential barriers and wells, injected holes and electrons diffused into dopedlayers and are localized in quantum-well by the energy barrier. Because of thenarrow region of quantum-well, increase the formation of hole-electron pairs,enhance the probability of Zr(OPh)₂q₂ exciton forming, reduce the quenching ofexcitons, and then improve formation efficiencyη₁ of exciton. It is just thecarriers'two-dimension characteristic that change density of energy state anddistribution of carriers effectively, and change radiate composite efficiencyeffectively. As a result of the above work, the luminance and efficiencyincreased nearly four times from 60cd/m² to 284cd/m², and meet the need ofindustry.