OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 13 — Jun. 21, 2010
  • pp: 13542–13546
« Show journal navigation

1.54 μm electroluminescence from p-Si anode organic light emitting diode with Bphen: Er(DBM)3phen as emitter and Bphen as electron transport material

F. Wei, Y. Z. Li, G. Z. Ran, and G. G. Qin  »View Author Affiliations


Optics Express, Vol. 18, Issue 13, pp. 13542-13546 (2010)
http://dx.doi.org/10.1364/OE.18.013542


View Full Text Article

Acrobat PDF (768 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

1.54 μm Si-anode organic light emitting devices with Er(DBM)3phen: Bphen and Bphen/Bphen:Cs2CO3 as the emissive and electron transport layers (the devices are referred to as the Bphen-based devices) have been investigated. In comparison with the AlQ-based devices with the same structure but with AlQ:Er(DBM)3Phen and AlQ as the emissive and electron transport layers, the maximum EL intensity and maximum power efficiency from the Bphen-based devices increase by a factor of 3 and 2.2, respectively. The optimized p-Si anode resistivity of the Bphen-based device of 10 Ω·cm is significantly lower than that of the AlQ-based device. The NIR EL improvement can be attributed to the energy transfer from Bphen to the Er complex and equilibrium of electron injection from the Sm/Au cathode and hole injection from the p-Si anode at a higher level.

© 2010 OSA

1. Introduction

The electroluminescence (EL) of organic light-emitting diodes (OLEDs) at near-infrared (NIR) region attracts increasing attention because of its applications in optical communication networks, low-cost NIR light sources and IR amplifiers [1

1. I. Izeddin, A. S. Moskalenko, I. N. Yassievich, M. Fujii, and T. Gregorkiewicz, “Nanosecond dynamics of the near-infrared photoluminescence of Er-doped SiO2 sensitized with Si nanocrystals,” Phys. Rev. Lett. 97(20), 207401 (2006). [CrossRef] [PubMed]

3

3. J.-C. G. Bünzli and C. Piguet, “Taking advantage of luminescent lanthanide ions,” Chem. Soc. Rev. 34(12), 1048–1077 (2005). [CrossRef] [PubMed]

]. The NIR luminescence of ~1.54 μm from erbium-containing materials has been widely investigated for a wide range of applications in optical telecommunications and Si photonics, because this wavelength lies in the minimum-loss transmission window of silica-based fibers. Since Gillin reported Silicon-based OLEDs using ErQ as emitting layers, many efforts have been done to obtain ~1.54 μm EL and Er3+ complexes have become a very active field of research for the 1.54-μm light-emitting devices [4

4. R. J. Curry, W. P. Gillin, A. P. Knights, and R. Gwilliam, “Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm,” Appl. Phys. Lett. 77(15), 2271–2273 (2000). [CrossRef]

6

6. R. G. Sun, Y. Z. Wang, Q. B. Zheng, H. J. Zhang, and A. J. Epstein, “1.54 μm infrared photoluminescence and electroluminescence from an erbium organic compound,” J. Appl. Phys. 87(10), 7589–7591 (2000). [CrossRef]

]. However, the EL of Er complex still behaves weak because its intra-configurational 4f-4f transitions are forbidden. Therefore, selecting a proper organic material with strong charge-transfer absorptions to sensitize Er3+ ion via antenna effect and acquire the emission at 1.54 μm is quite useful to enhance the NIR emission property [7

7. S. V. Eliseeva and J.-C. G. Bünzli, “Lanthanide luminescence for functional materials and bio-sciences,” Chem. Soc. Rev. 39(1), 189–227 (2009). [CrossRef] [PubMed]

].

2. Experimental

The near infrared electroluminescence (EL) was driven by square pulses with a frequency of 22 Hz and a duty cycle of 1: 1, and measured by a ADC 403L (Applied Detector, Fresno, CA) liquid-nitrogen cooled Ge detector at room temperature. Power efficiency was determined by source meter (Keithley 2400) with a calibrated InGaAs photodiode Module (Hamamatsu G6121). Photoluminescence (PL) of Bphen thin film was performed by using a microzone confocal Raman spectrometer (LabRam HR 800) and the absorption of Er(DBM)3Phen was examined using a UV-Vis spectrophotometer (Lambda 35).

The devices were not encapsulated and all the measurements were carried out in atmosphere at room temperature.

3. Results and discussion

The typical top-emission electroluminescence spectra for the Si-based OLEDs are shown in Fig. 2
Fig. 2 EL spectra measured at the current density of 200 mA/cm2 for Bphen-based device with 10 Ω·cm p-Si anode, the AlQ-Bphen device with 10 Ω·cm p-Si anode and the AlQ-based devices with 40 Ω·cm p-Si anode. The inset shows the PL spectrum of Bphen film (λex=325 nm) and absorption spectrum of Er(DBM)3Phen.
. It can be seen that all the devices show the typical 1.54 μm peak which is the characteristic emission of Er3+ ions, attributing to the transitions, 4I13/2 ~4I15/2. At the same current density of 200 mA/cm2, the Bphen-based device exhibits near four and six times higher EL intensity at 1.54 μm than that of the AlQ-Bphen and AlQ-based devices respectively.

To study the effect of electric resistivities of p-Si anodes to the NIR EL, we have fabricated Bphen-based devices each with a 40, 20, 10, 1 and 0.08 Ω·cm p-Si anode. Figure 3
Fig. 3 The NIR power of the Bphen-based and AlQ-based devices versus resistivity of the p-Si anodes.
summarized the maximum emission intensity of these devices. As it can be observed, the power efficiency of Bphen-based devices strongly depends on electrical resistivity of the passivated p-Si anode, and the optimum electrical resistivity for the passivated p-Si anode is 10 Ω·cm. However, to AlQ-based devices, the best electrical resistivity we can obtain for the passivated p-Si anode is 40 Ω·cm. This result implies that when electron current is enhanced by using CsPh instead of AlQ, hole current can be enhanced by simply reducing the resistivity of the passivated p-Si anode to 10 Ω·cm for matching electron current.

The NIR irradiation-voltage and current density-voltage curves for Bphen-based device with 10 Ω·cm p-Si anode are plotted in Fig. 4
Fig. 4 Near infrared electroluminescence power-voltage and current density-voltage curves for Bphen-based device with 10 Ω·cm p-Si anode.
. The NIR irradiation curve of Bphen-based device shows an apparently sublinear increase with current density up to the maximum current density of 700 mA/cm2 that we used and the maximum NIR power of 0.93 μW/cm2 is acquired at the current density of 635 mA/cm2 (12.5 V). Besides, it is worth noting that the NIR emission turn-on voltage of the Bphen-based devices is ~7 V which is farther lower than that of reported ErQ-based device [4

4. R. J. Curry, W. P. Gillin, A. P. Knights, and R. Gwilliam, “Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm,” Appl. Phys. Lett. 77(15), 2271–2273 (2000). [CrossRef]

]. The maximum EL intensity and maximum power efficiency of the Bphen-based device with 10 Ω·cm p-Si anode is increased by a factor of 3 and 2.2, comparing to the AlQ-based device with 40 Ω·cm p-Si anode.

The improvement of the power efficiency should be ascribed to two aspects as follows. Firstly, comparing with AlQ, Bphen has a relative higher electron injection capability [14

14. W. Q. Zhao, G. Z. Ran, W. J. Xu, and G. G. Qin, “Passivated p-type silicon: Hole injection tunable anode material for organic light emission,” Appl. Phys. Lett. 92(7), 073303 (2008). [CrossRef]

]. Thus in the AlQ-based device, to keep a carrier balance, a relatively lower hole injection from higher-resistivity p-Si anode is needed to match the electron injection. Correspondingly, the resistivity of p-Si anode should be no less than 40 Ω·cm. Whereas in Bphen-based device, the hole injection from the p-Si anode should be enhanced by decreasing its electrical resistivity to keep a carrier balance. Consequently, the maximum power efficiency from the Bphen-based device is larger than that of the AlQ-based device. Secondly, in Bphen-based device, it can be seen a large overlap between PL spectrum of Bphen and absorption spectrum of the ligands (DBM and phen) as plotted in the inset of Fig. 2. This implies an efficient Föster energy transfer process from Bphen to Er(DBM)3phen which may increasing NIR emission from Er3+ [15

15. R. H. C. Tan, J. M. Pearson, Y. Zheng, P. B. Wyatt, and W. P. Gillin, “Evidence for erbium-erbium energy migration in erbium(III) bis(perfluoro-p-tolyl)phosphinate,” Appl. Phys. Lett. 92(10), 103303 (2008). [CrossRef]

17

17. D. Zhang, W. Li, B. Chu, X. Li, L. Han, J. Zhu, T. Li, D. Bi, D. Yang, F. Yan, H. Liu, and D. Wang, “Sensitized photo- and electroluminescence from Er complexes mixed with Ir complex,” Appl. Phys. Lett. 92(9), 093501 (2008). [CrossRef]

]. However, in AlQ-based device, there is no overlap energy transfer from an AlQ singlet state to Er complex [8

8. W. Q. Zhao, P. F. Wang, G. Z. Ran, G. L. Ma, B. R. Zhang, W. M. Liu, S. K. Wu, L. Dai, and G. G. Qin, “1.54 μm Er3+ electroluminescence from an erbium-compound-doped organic light emitting diode with a p-type silicon anode,” J. Phys. D Appl. Phys. 39(13), 2711–2714 (2006). [CrossRef]

], resulting in an inefficient EL at 1.54 μm. Thus, in Bphen-based device, the EL of Er(DBM)3phen can be obtained in two ways. Except directly from trapped carriers in emissive layer, the EL can be achieved from the energy transfer process [18

18. L. N. Sun, H. J. Zhang, L. S. Fu, Q. G. Meng, C. Y. Peng, and J. B. Yu, “A new sol-gel material doped with an Erbium complex and its potential optical-amplification application,” Adv. Funct. Mater. 15(6), 1041–1048 (2005). [CrossRef]

]. Since holes are injected from p-Si anode and transported into the Er doped Bphen emissive layer, the energy from Bphen can be effectively transferred to the Er complex. Then ligands DBM and phen are able to transfer the absorbed energy to the central metal Er3+ ion according to the antenna effect. Further investigation for the EL mechanism is still ongoing.

3. Conclusion

In summary, we demonstrate an improved 1.54 μm NIR emission from Si-anode OLED using Er(DBM)3Phen doped Bphen as emissive layer and Bphen as ETL. We conclude that the enhancement of the NIR EL attribute to both the higher electron transport ability of Bphen and the intersystem energy transfer between Er complex and Bphen. The results also indicate that a suitable p-Si anode for the devices plays an important role for the NIR emission because of the balance between electron- and hole-injection can optimize the NIR light-emitting efficiency.

Acknowledgement

This work was supported by the National Natural Science Foundation of China (Grant Nos. 50732001, 10674012, 10874001, and 60877022), the National 973 Project (Grant No. 2007CB613402) China Postdoctoral Science Foundation.

References and links

1.

I. Izeddin, A. S. Moskalenko, I. N. Yassievich, M. Fujii, and T. Gregorkiewicz, “Nanosecond dynamics of the near-infrared photoluminescence of Er-doped SiO2 sensitized with Si nanocrystals,” Phys. Rev. Lett. 97(20), 207401 (2006). [CrossRef] [PubMed]

2.

Y. Yin, K. Sun, W. J. Xu, G. Z. Ran, G. G. Qin, S. M. Wang, and C. Q. Wang, “1.53 μm photo- and electroluminescence from Er3+ in erbium silicate,” J. Phys. Condens. Matter 21(1), 012204 (2009). [CrossRef] [PubMed]

3.

J.-C. G. Bünzli and C. Piguet, “Taking advantage of luminescent lanthanide ions,” Chem. Soc. Rev. 34(12), 1048–1077 (2005). [CrossRef] [PubMed]

4.

R. J. Curry, W. P. Gillin, A. P. Knights, and R. Gwilliam, “Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm,” Appl. Phys. Lett. 77(15), 2271–2273 (2000). [CrossRef]

5.

R. J. Curry and W. P. Gillin, “1.54 μm electroluminescence from erbium (III) tris(8-hydroxyquinoline) (ErQ)-based organic light-emitting diodes,” Appl. Phys. Lett. 75(10), 1380–1382 (1999). [CrossRef]

6.

R. G. Sun, Y. Z. Wang, Q. B. Zheng, H. J. Zhang, and A. J. Epstein, “1.54 μm infrared photoluminescence and electroluminescence from an erbium organic compound,” J. Appl. Phys. 87(10), 7589–7591 (2000). [CrossRef]

7.

S. V. Eliseeva and J.-C. G. Bünzli, “Lanthanide luminescence for functional materials and bio-sciences,” Chem. Soc. Rev. 39(1), 189–227 (2009). [CrossRef] [PubMed]

8.

W. Q. Zhao, P. F. Wang, G. Z. Ran, G. L. Ma, B. R. Zhang, W. M. Liu, S. K. Wu, L. Dai, and G. G. Qin, “1.54 μm Er3+ electroluminescence from an erbium-compound-doped organic light emitting diode with a p-type silicon anode,” J. Phys. D Appl. Phys. 39(13), 2711–2714 (2006). [CrossRef]

9.

S.-Y. Chen, T.-Y. Chua, J.-F. Chen, C.-Y. Su, and C. H. Chen, “Stable inverted bottom-emitting organic electroluminescent devices with molecular doping and morphology improvement,” Appl. Phys. Lett. 89(5), 053518 (2006). [CrossRef]

10.

H. Liang, Z. Zheng, B. Chen, Q. Zhang, and H. Ming, “Optical studies of Er(DBM)3Phen containing methyl methacrylate solution and poly(methyl methacrylate) matrix,” Mater. Chem. Phys. 86(2-3), 430–434 (2004). [CrossRef]

11.

Q. Xin, W. L. Li, G. B. Che, W. M. Su, X. Y. Sun, B. Chu, and B. Li, “Improved electroluminescent performances of europium-complex based devices by doping into electron-transporting/hole-blocking host,” Appl. Phys. Lett. 89(22), 223524 (2006). [CrossRef]

12.

L. R. Melby, N. J. Rose, E. Abramson, and J. C. Caris, “Synthesis and Fluorescence of Some Trivalent Lanthanide Complexes,” J. Am. Chem. Soc. 86(23), 5117–5125 (1964). [CrossRef]

13.

G. G. Qin, A. G. Xu, G. L. Ma, G. Z. Ran, Y. P. Qiao, B. R. Zhang, W. X. Chen, and S. K. Wu, “A top-emission organic light-emitting diode with a silicon anode and an Sm/Au cathode,” Appl. Phys. Lett. 85(22), 5406–5408 (2004). [CrossRef]

14.

W. Q. Zhao, G. Z. Ran, W. J. Xu, and G. G. Qin, “Passivated p-type silicon: Hole injection tunable anode material for organic light emission,” Appl. Phys. Lett. 92(7), 073303 (2008). [CrossRef]

15.

R. H. C. Tan, J. M. Pearson, Y. Zheng, P. B. Wyatt, and W. P. Gillin, “Evidence for erbium-erbium energy migration in erbium(III) bis(perfluoro-p-tolyl)phosphinate,” Appl. Phys. Lett. 92(10), 103303 (2008). [CrossRef]

16.

Z. Li, J. Yu, L. Zhou, H. Zhang, R. Deng, and Z. Guo, “1.54 μm near-infrared photoluminescent and electroluminescent properties of a new Erbium (III) organic complex,” Org. Electron. 9(4), 487–494 (2008). [CrossRef]

17.

D. Zhang, W. Li, B. Chu, X. Li, L. Han, J. Zhu, T. Li, D. Bi, D. Yang, F. Yan, H. Liu, and D. Wang, “Sensitized photo- and electroluminescence from Er complexes mixed with Ir complex,” Appl. Phys. Lett. 92(9), 093501 (2008). [CrossRef]

18.

L. N. Sun, H. J. Zhang, L. S. Fu, Q. G. Meng, C. Y. Peng, and J. B. Yu, “A new sol-gel material doped with an Erbium complex and its potential optical-amplification application,” Adv. Funct. Mater. 15(6), 1041–1048 (2005). [CrossRef]

OCIS Codes
(160.4890) Materials : Organic materials
(230.3670) Optical devices : Light-emitting diodes

ToC Category:
Optical Devices

History
Original Manuscript: February 16, 2010
Revised Manuscript: April 7, 2010
Manuscript Accepted: April 13, 2010
Published: June 9, 2010

Citation
F. Wei, Y. Z. Li, G. Z. Ran, and G. G. Qin, "1.54 μm electroluminescence from p-Si anode organic light emitting diode with Bphen: Er(DBM)3phen as emitter and Bphen as electron transport material," Opt. Express 18, 13542-13546 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-13-13542


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. I. Izeddin, A. S. Moskalenko, I. N. Yassievich, M. Fujii, and T. Gregorkiewicz, “Nanosecond dynamics of the near-infrared photoluminescence of Er-doped SiO2 sensitized with Si nanocrystals,” Phys. Rev. Lett. 97(20), 207401 (2006). [CrossRef] [PubMed]
  2. Y. Yin, K. Sun, W. J. Xu, G. Z. Ran, G. G. Qin, S. M. Wang, and C. Q. Wang, “1.53 μm photo- and electroluminescence from Er3+ in erbium silicate,” J. Phys. Condens. Matter 21(1), 012204 (2009). [CrossRef] [PubMed]
  3. J.-C. G. Bünzli and C. Piguet, “Taking advantage of luminescent lanthanide ions,” Chem. Soc. Rev. 34(12), 1048–1077 (2005). [CrossRef] [PubMed]
  4. R. J. Curry, W. P. Gillin, A. P. Knights, and R. Gwilliam, “Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm,” Appl. Phys. Lett. 77(15), 2271–2273 (2000). [CrossRef]
  5. R. J. Curry and W. P. Gillin, “1.54 μm electroluminescence from erbium (III) tris(8-hydroxyquinoline) (ErQ)-based organic light-emitting diodes,” Appl. Phys. Lett. 75(10), 1380–1382 (1999). [CrossRef]
  6. R. G. Sun, Y. Z. Wang, Q. B. Zheng, H. J. Zhang, and A. J. Epstein, “1.54 μm infrared photoluminescence and electroluminescence from an erbium organic compound,” J. Appl. Phys. 87(10), 7589–7591 (2000). [CrossRef]
  7. S. V. Eliseeva and J.-C. G. Bünzli, “Lanthanide luminescence for functional materials and bio-sciences,” Chem. Soc. Rev. 39(1), 189–227 (2009). [CrossRef] [PubMed]
  8. W. Q. Zhao, P. F. Wang, G. Z. Ran, G. L. Ma, B. R. Zhang, W. M. Liu, S. K. Wu, L. Dai, and G. G. Qin, “1.54 μm Er3+ electroluminescence from an erbium-compound-doped organic light emitting diode with a p-type silicon anode,” J. Phys. D Appl. Phys. 39(13), 2711–2714 (2006). [CrossRef]
  9. S.-Y. Chen, T.-Y. Chua, J.-F. Chen, C.-Y. Su, and C. H. Chen, “Stable inverted bottom-emitting organic electroluminescent devices with molecular doping and morphology improvement,” Appl. Phys. Lett. 89(5), 053518 (2006). [CrossRef]
  10. H. Liang, Z. Zheng, B. Chen, Q. Zhang, and H. Ming, “Optical studies of Er(DBM)3Phen containing methyl methacrylate solution and poly(methyl methacrylate) matrix,” Mater. Chem. Phys. 86(2-3), 430–434 (2004). [CrossRef]
  11. Q. Xin, W. L. Li, G. B. Che, W. M. Su, X. Y. Sun, B. Chu, and B. Li, “Improved electroluminescent performances of europium-complex based devices by doping into electron-transporting/hole-blocking host,” Appl. Phys. Lett. 89(22), 223524 (2006). [CrossRef]
  12. L. R. Melby, N. J. Rose, E. Abramson, and J. C. Caris, “Synthesis and Fluorescence of Some Trivalent Lanthanide Complexes,” J. Am. Chem. Soc. 86(23), 5117–5125 (1964). [CrossRef]
  13. G. G. Qin, A. G. Xu, G. L. Ma, G. Z. Ran, Y. P. Qiao, B. R. Zhang, W. X. Chen, and S. K. Wu, “A top-emission organic light-emitting diode with a silicon anode and an Sm/Au cathode,” Appl. Phys. Lett. 85(22), 5406–5408 (2004). [CrossRef]
  14. W. Q. Zhao, G. Z. Ran, W. J. Xu, and G. G. Qin, “Passivated p-type silicon: Hole injection tunable anode material for organic light emission,” Appl. Phys. Lett. 92(7), 073303 (2008). [CrossRef]
  15. R. H. C. Tan, J. M. Pearson, Y. Zheng, P. B. Wyatt, and W. P. Gillin, “Evidence for erbium-erbium energy migration in erbium(III) bis(perfluoro-p-tolyl)phosphinate,” Appl. Phys. Lett. 92(10), 103303 (2008). [CrossRef]
  16. Z. Li, J. Yu, L. Zhou, H. Zhang, R. Deng, and Z. Guo, “1.54 μm near-infrared photoluminescent and electroluminescent properties of a new Erbium (III) organic complex,” Org. Electron. 9(4), 487–494 (2008). [CrossRef]
  17. D. Zhang, W. Li, B. Chu, X. Li, L. Han, J. Zhu, T. Li, D. Bi, D. Yang, F. Yan, H. Liu, and D. Wang, “Sensitized photo- and electroluminescence from Er complexes mixed with Ir complex,” Appl. Phys. Lett. 92(9), 093501 (2008). [CrossRef]
  18. L. N. Sun, H. J. Zhang, L. S. Fu, Q. G. Meng, C. Y. Peng, and J. B. Yu, “A new sol-gel material doped with an Erbium complex and its potential optical-amplification application,” Adv. Funct. Mater. 15(6), 1041–1048 (2005). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 
Fig. 4
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited