Blue phosphorescent organic light-emitting device with double

Blue phosphorescent organic light-emitting device with double

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Blue phosphorescent organic light-emitting device with double emitting layer Jiun-Haw Lee, 1, a ! Chih-Lun Huang, 1 Chih-Hung Hsiao, 1 Man-Kit Leung, 2 Chih-Chiang Yang, 2 and Chun-Chieh Chao 2 1 Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Roosevelt Road, Sec. 4, Taipei 10617, Taiwan 2 Department of Chemistry and Institute of Polymer Science and Engineering, National Taiwan University, No. 1, Roosevelt Road, Sec. 4, Taipei 10617, Taiwan s Received 23 January 2009; accepted 8 May 2009; published online 1 June 2009 d In this paper, we demonstrated a blue phosphorescent organic light-emitting device s OLED d with a higher current-efFciency and a lower driving-voltage using conventional iridium s III d bis f 4,6- s di-±uorophenyl d -pyridinato- N ,C2 8 g picolinate s ²Irpic d doped in the double emitting layer s DEML d , which consists of a hole- and an electron-transporting material, N , N 8 -dicarbazolyl-3,5-benzene s mCP d and 2,2 8 -bis f 5-phenyl-2- s 1,3,4 d oxadazolyl g biphenyl s OXD d , respectively. Compared to OLEDs with only single mCP- and OXD-EML, current-efFciency of the optimized DEML-OLED increases by 30.82% and 141.37%, combining with a voltage reduction of 0.34 and 0.59 V at 50 mA / cm 2 , which comes from the better charge balance in DEML. © 2009 American Institute of Physics . f DOI: 10.1063/1.3147866 g Organic light-emitting device s OLED d is one of the most promising display and lighting technologies. 1 6 By doping phosphorescent emitters both in the hole- and electron- transporting hosts as the double emitting layer s DEML d structure, it shows a signiFcant improvement in device efFciency. 7 10 Recently, Yook et al. 10 presented the DEML of the combination of the hole- and an electron-transporting hosts, N , N 8 -dicarbazolyl-3,5-benzene s mCP d and 1,3- bis s triphenylsilyl d benzene s UGH3 d , respectively, for the blue emitter iridium s III d bis f 4,6- s di-±uorophenyl d -pyridinato- N 8 g picolinate s ²Irpic d . However, the highest occupied molecular orbital s HOMO d value of UGH3 is about 7.1 eV, which may result in a larger barrier for holes injection and hence a high driving voltage. In this paper, we proposed a blue phosphorescent OLED with ²Irpic by using an oxadiazole s OXD d derivative, 2,2 8 -bis f 5-phenyl-2- s 1,3,4 d oxadazolyl g biphenyl, as an electron-transporting host material. 11 Combining with the hole-transporting mCP, a DEML device with lower driving voltage and higher current efFciency can be achieved simultaneously. Our devices were fabricated on the indium-tin-oxide glass substrates with the active region size of 2 mm 2 . 12 After oxygen plasma treatment, substrate was loaded into the ther- mal evaporator for thin Flm deposition. Then, devices were encapsulated by a cover glass and UV sealant in the glove box. Luminance-current density-voltage s L - J - V d characteris- tics were measured by Keithley 2400 and Minolta CS-1000 spectrometer. Table I illustrates the device structures in this study. N , N -Bis s naphthalen-1-yl d - N , N -bis s phenyl d benzi- dine s NPB d , 4,4 8 ,4 9 -tris- s N
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/27/2011 for the course CHEM 2211L taught by Professor T.a. during the Spring '08 term at University of Georgia Athens.

Page1 / 4

Blue phosphorescent organic light-emitting device with double

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online