Abstract
A highly efficient tandem organic light-emitting device (OLED) has been fabricated by using an effective bipolar connecting layer structure. The connecting layers were made up of a layer of magnesium (Mg): 2,7-dipyrenyl-9,9-diphenyl fluorene (N-DPF) and a layer of tungsten trioxide (WO3). Such a connecting layer structure permits efficient opposite holes and electrons flowing into two adjacent emitting units. The current efficiency of the two-unit tandem device can be dramatically enhanced by more than four times compared with that of the conventional single-unit device. At 60 mA/cm2, the current efficiency of the tandem OLED using the connecting layers of Mg: N-DPF/WO3 was about 8.15 cd/A. The results can be marked as a breakthrough approach to improve the current efficiency and brightness of OLEDs. Furthermore, a model of the carrier tunneling into light-emitting units is proposed based on carrier balance and field-assisted tunneling. It indicates that the connecting layer structure functions as the origin of high efficiency for the tandem OLEDs.
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C. Jenny, L. Guglielmo, Nat. Photonics 4, 438 (2010)
R. Madhava, T. Huang, Y. Su, Y. Huang, Devices J. Electrochem. Soc. 157, H69 (2010)
Q. Bao, J. Yang, Y. Li, J. Tang, Appl. Phys. Lett. 97, 063303 (2010)
L. Niu, Y. Guan, Y. Ren, C. Kong, Y. Ma, Y. Liang, Sci. China Ser. E – Tech. Sci. 52, 95 (2009)
J. Sun, X. Zhu, H. Peng, M. Wong, H. Kwok, Appl. Phys. Lett. 87, 093504 (2005)
P. Burrows, S. Forrest, S. Sibley, M. Thompson, Appl. Phys. Lett. 69, 2959 (1996)
F. Guo, D. Ma, Appl. Phys. Lett. 87, 173510 (2005)
C. Chang, J. Chen, S. Hwang, C. Chen, Appl. Phys. Lett. 87, 253501 (2005)
C. Chen, Y. Lu, C. Wu, E. Wu, C. Chu, Y. Yang, Appl. Phys. Lett. 87, 241121 (2005)
H. Kanno, R. Holmes, Y. Sun, S. Cohen, S. Forrest, Adv. Mater. 18, 339 (2006)
L. Liao, K. Klubek, C. Tang, Appl. Phys. Lett. 84, 167 (2004)
T. Cho, C. Lin, C. Wu, Appl. Phys. Lett. 88, 111106 (2006)
T. Tsutsui, M. Terai, Appl. Phys. Lett. 84, 440 (2004)
C. Law, K. Lau, M. Fung, M. Chan, F. Wong, C. Lee, S. Lee, Appl. Phys. Lett. 89, 133511 (2006)
M. Chan, S. Lai, K. Lau, M. Fung, C. Lee, S. Lee, Adv. Funct. Mater. 17, 2509 (2007)
S. Tao, C. Lee, S. Lee, Appl. Phys. Lett. 91, 013507 (2007)
S. Tao, L. Niu, J. Yu, Y. Jiang, X. Zhang, J. Lumin. 130, 70 (2010)
T. Tsutsui, S. Lee, K. Fujita, Appl. Phys. Lett. 85, 852382 (2004)
M. Kröger, S. Hamwi, J. Meyer, T. Dobbertin, T. Riedl, W. Kowalsky, H.-H. Johannes, Phys. Rev. B 75, 235321 (2007)
W. Brütting, S. Berleb, A. Mück, Org. Electron. 2, 1 (2001)
C. Chang, S. Wen, C. Chen, J. Fang, Jpn. J. Appl. Phys. 43, 6418 (2004)
T. Cho, C. Lin, C. Wu, Appl. Phys. Lett. 88, 111106 (2006)
S. Fleischer, P. Lai, J. Appl. Phys. 72, 5711 (1992)
X. Qi, N. Li, R. Stephen, J. Appl. Phys. 107, 014514 (2010)
D. Sathaiya, S. Karmalkar, J. Appl. Phys. 99, 093701 (2006)
A. Rajagopal, A. Kahn, J. Appl. Phys. 84, 355 (1998)
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Niu, L., Guan, Y., Kong, C. et al. Highly efficient bipolar connecting layers for tandem organic light-emitting devices. Appl. Phys. B 105, 857–862 (2011). https://doi.org/10.1007/s00340-011-4703-0
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DOI: https://doi.org/10.1007/s00340-011-4703-0