Study On Transparent OLED And Full-color Passive-matrix OLEDs Displays

Organic light-emitting diode (OLED) is also named as organic electroluminescencedevice.The OLED technology develops very quickly because of its advantages,suchas self-emission,fast response,full solid device,large viewing angle,ultra-thinstructure,and wide-temperature operating range.1.Two kinds of OLED with Lanthanum hexaborides (LaB₆) as transparent cathodewere fabricated.The structures of two kinds of OLED are LaB₆/Alq₃/NPD/Au andITO/TPD/Alq₃/LaB₆,respectively.LaB₆ film,with transparency of～70% and sheetresistance of 35Ω/â–¡when the thickness of film is about 1800(?),was prepared by theelectrons-beam evaporation.Turn-on voltage of LaB₆/Alq₃/NPD/Au is 2.4V,andmaximum current efficiency is 2.46cd/A at 2.6V.Peak wavelength of EL spectrum is534nm at 15V,and chromaticity coordinates is (0.287,0.652).The device with thestructure of ITO/TPD/Alq₃/LaB₆ is a transparent OLED,whose turn-on voltage is 2.8V,maximum current efficiency is 4.36cd/A at 5.0V and luminance reach 5650cd/m² at 17V.Compared to the peak wavelength of spectra emitted from anode,the peak of spectraemitted from LaB₆ transparent cathode shifts～8nm to longer wavelength,due in part tomicrocave effect.2.A systematic and numerical analysis of the simple equivalent and exact equivalentcircuit of PMOLEDS was presented,and the crosstalk of PMOLEDS was analyzed.IfOLEDs have a good rectification,the crosstalk will have a very minor impact on theimage non-uniformity of PMOLEDs.Voltage drop on the electrode was quantitativelyanalyzed.Because the current dependence of voltage of OLED must meet the powerrelation,the minor voltage applied to each pixel will enable relative difference ofcurrent.So current-source is usually used to drive PMOLEDs.A mathematical model tocalculate the power consumption of PMOLEDs was presented.The models demonstratethat the power of dual-panel PMOLEDs can be significantly reduced compared withthat of single-panel PMOLEDs.Two 2.5-in.128×64-pixel green small moleculePMOLEDs was fabricated.One is single-panel,and the other is dual-panel.Comparedthe power consumption of single-panel with that of dual-panel PMOLEDs,the latter device show a reduction of 25% when both are operated at the average luminance of100cd/m².3.The pattern of substrate of full-color PMOLEDs (128×160),four kinds of photomask and two kinds of shadow mask,FPC and COF was designed.4.Driving circuits using pre-charge technology of full-color PMOLEDs wasdesigned.By applying pre-charge,the pixel voltage reaches the target level quickly,andthe diode current flow at the corresponding desired level.The charged level of red,green and blue OLED was set to 3.0V,2.0V and 2.9V,respectively.The displayfeatures that control circuit can transform 18 bits gray-scale data from a PC to theOLED panel via a DVI channel.The lifetime of panel was estimated over 5000hbecause of the use of dual-scan driving technology,and the power consumption of thedisplay was about 300mw at the average luminance of 40cd/m².5.Green doped OLED with two different HIL,2-TNATA and CuPc were studied.Measurement of I-V-L curves two kinds of OLED show a ohmic contact betweenorganic layer and the electrode interface under low forward bias voltage (＜5.7V),andI-V in agreement with trap-charge limited conduction under high forward bias (＞5.7V).The efficiency of OLED using 2-TNATA as HIL is better than that of CuPc.Moreover,device with the different thickness of 2-TNATA was studied.The performance ofdevice with the 35nm thickness of 2-TNATA is the best.The luminance and currentefficiency is 3280cd/m² and 1.377cd/A at 13V.The thicknesses of HIL have a minorimpact on EL spectrum of device.6.Influences of different doping concentration of C-545T on OLED were studied.The device with 1.5 wt% doping concentration shows a maximum power efficiency of6.16cd/A,and a luminance of 10650cd/m² at 19.5V.Doping concentration of C-545Thas a great impact on EL spectrum,and there is a～26nm red-shift of the spectral peak.