Inserting a hole-buffer layer is an effective way to enhance emission efficiency of electroluminescence devices. We have successfully synthesized a new hole-buffer material PSB composed of pyrene, Schiff base and trihydroxy tert-butyl groups by the Suzuki-coupling reaction. The HOMO and LUMO lev-els were -6.33 eV and -2.55 eV, respectively, as estimated from cyclic volt-ammograms. In addition, homogeneous films (rms roughness ~2 nm) were readily obtained by spin-coating process. Multilayer polymer light-emitting diodes, ITO/PEDOT:PSS/PSB/SY/LiF/Al, have been fabricated using PSB as hole-buffer layer (HBL). Inserting PSB as HBL significantly enhances the per-formance (maximum luminance: 26,439 cd/m2, maximum current efficiency: 7.03 cd/A), compared with the one without PSB (9802 cd/m2, 2.43 cd/A). It is also superior to the device with conventional BCP as hole-blocking layer (ITO/PEDOT:PSS/SY/BCP/LiF/Al: 15,496 cd/m2, 5.56 cd/A). Current results strongly indicate that the PSB is a potential hole-buffer material for electrolu-minescent devices.
References
[1]
Burroughes, J., Bradley, D., Brown, A., Marks, R., Mackay, K., Friend, R., Burns, P. and Holmes, A. (1990) Light-Emitting Diodes Based on Conjugated Polymers. Nature, 347, 539-541. https://doi.org/10.1038/347539a0
[2]
Burrows, P.E., Graff, G.L., Gross, M.E., Martin, P.M., Shi, M.-K., Hall, M., Mast, E., Bonham, C., Bennett, W. and Sullivan, M.B. (2001) Ultra Barrier Flexible Substrates for Flat Panel Displays. Displays, 22, 65-69.
https://doi.org/10.1016/S0141-9382(00)00064-0
[3]
Sugimoto, A., Ochi, H., Fujimura, S., Yoshida, A., Miyadera, T. and Tsuchida, M. (2004) Flexible OLED Displays Using Plastic Substrates. IEEE Journal of Selected Topics in Quantum Electronics, 10, 107-114.
https://doi.org/10.1109/JSTQE.2004.824112
[4]
Qiu, Y., Gao, Y., Wei, P. and Wang, L. (2002) Organic Light-Emitting Diodes with Improved Hole-Electron Balance by Using Copper Phthalocyanine/Aromatic Diamine Multiple Quantum Wells. Applied Physics Letters, 80, 2628-2630.
https://doi.org/10.1063/1.1468894
[5]
Yin, S., Yi, Y., Li, Q., Yu, G., Liu, Y. and Shuai, Z. (2006) Balanced Carrier Transports of Electrons and Holes in Silole-Based Compounds—A Theoretical Study. Journal of Physical Chemistry A, 110, 7138-7143. https://doi.org/10.1021/jp057291o
[6]
Yamashita, Y. (2009) Organic Semiconductors for Organic Field-Effect Transistors. Science and Technology of Advanced Materials, 10, Article ID: 024313.
https://doi.org/10.1088/1468-6996/10/2/024313
[7]
Hung, L., Tang, C.W. and Mason, M.G. (1997) Enhanced Electron Injection in Organic Electroluminescence Devices Using an Al/LiF Electrode. Applied Physics Letters, 70, 152-154. https://doi.org/10.1063/1.118344
[8]
Brown, T., Kim, J., Friend, R., Cacialli, F., Daik, R. and Feast, W. (1999) Built-In Field Electroabsorption Spectroscopy of Polymer Light-Emitting Diodes Incorporating a Doped Poly (3, 4-Ethylene Dioxythiophene) Hole Injection Layer. Applied Physics Letters, 75, 1679-1681. https://doi.org/10.1063/1.124789
[9]
Adamovich, V.I., Cordero, S.R., Djurovich, P.I., Tamayo, A., Thompson, M.E., D’Andrade, B.W. and Forrest, S.R. (2003) New Charge-Carrier Blocking Materials for High Efficiency OLEDs. Organic Electronics, 4, 77-87.
https://doi.org/10.1016/j.orgel.2003.08.003
[10]
Lin, W.C., Lin, H.W., Mondal, E. and Wong, K.T. (2015) Efficient Solution-Processed Green and White Phosphorescence Organic Light-Emitting Diodes Based on Bipolar Host Materials. Organic Electronics, 17, 1-8.
https://doi.org/10.1016/j.orgel.2014.11.002
[11]
Gao, H., Qin, C., Zhang, H., Wu, S., Su, Z.M. and Wang, Y. (2008) Theoretical Characterization of a Typical Hole/Exciton-Blocking Material Bathocuproine and Its Analogues. Journal of Physical Chemistry A, 112, 9097-9103.
https://doi.org/10.1021/jp804308e
[12]
Ikai, M., Tokito, S., Sakamoto, Y., Suzuki, T. and Taga, Y. (2001) Highly Efficient Phosphorescence from Organic Light-Emitting Devices with an Exciton-Block Layer. Applied Physics Letters, 79, 156-158. https://doi.org/10.1063/1.1385182
[13]
Su, H.-C. and Hsu, J.-H. (2015) Improving the Carrier Balance of Light-Emitting Electrochemical Cells Based on Ionic Transition Metal Complexes. Dalton Transactions, 44, 8330-8345. https://doi.org/10.1039/C4DT01675K
[14]
Xia, Y.-J., Lin, J., Tang, C., Yin, K., Zhong, G.-Y., Ni, G., Peng, B., Gan, F.-X. and Huang, W. (2006) High-Efficiency Blue-Emitting Organic Light-Emitting Devices with 4, 4’, 4’’-Tris (N-Carbazolyl)-Triphenylamine as the Hole/Exciton-Blocking Layer. Journal of Physics D: Applied Physics, 39, 4987.
https://doi.org/10.1088/0022-3727/39/23/013
[15]
Tadayyon, S.M., Grandin, H.M., Griffiths, K., Norton, P.R., Aziz, H. and Popovic, Z.D. (2004) CuPc Buffer Layer Role in OLED Performance: A Study of the Interfacial Band Energies. Organic Electronics, 5, 157-166.
https://doi.org/10.1016/j.orgel.2003.10.001
[16]
Chou, S.-Y. and Chen, Y. (2016) Hole-Buffer Polymer Composed of Alternating p-Terphenyl and Tetraethylene Glycol Ether Moieties: Synthesis and Application in Polymer Light-Emitting Diodes. Journal of Polymer Science Part A: Polymer Chemistry, 54, 785-794. https://doi.org/10.1002/pola.27911
[17]
Lee, S.J., Lee, S.E., Lee, D.H., Koo, J.R., Lee, H.W., Yoon, S.S., Park, J. and Kim, Y.K. (2014) Effect of Broad Recombination Zone in Multiple Quantum Well Structures on Lifetime and Efficiency of Blue Organic Light-Emitting Diodes. Japanese Journal of Applied Physics, 53, Article ID: 101601. https://doi.org/10.7567/JJAP.53.101601
[18]
Forsythe, E., Abkowitz, M. and Gao, Y. (2000) Tuning the Carrier Injection Efficiency for Organic Light-Emitting Diodes. Journal of Physical Chemistry B, 104, 3948-3952. https://doi.org/10.1021/jp993793o
[19]
Shibata, M., Sakai, Y. and Yokoyama, D. (2015) Advantages and Disadvantages of Vacuum-Deposited and Spin-Coated Amorphous Organic Semiconductor Films for Organic Light-Emitting Diodes. Journal of Materials Chemistry C, 3, 11178-11191. https://doi.org/10.1039/C5TC01911G
[20]
Duan, L., Hou, L., Lee, T.-W., Qiao, J., Zhang, D., Dong, G., Wang, L. and Qiu, Y. (2010) Solution Processable Small Molecules for Organic Light-Emitting Diodes. Journal of Materials Chemistry, 20, 6392-6407. https://doi.org/10.1039/b926348a
[21]
Otsubo, T., Aso, Y. and Takimiya, K. (2002) Functional Oligothiophenes as Advanced Molecular Electronic Materials. Journal of Materials Chemistry, 12, 2565-2575. https://doi.org/10.1039/b203780g
[22]
Ferguson, J. (1958) Absorption and Fluorescence Spectra of Crystalline Pyrene. Journal of Chemical Physics, 28, 765-768. https://doi.org/10.1063/1.1744267
[23]
Hsu, P.-F. and Chen, Y. (2018) Synthesis of a Pyrene-Derived Schiff Base and Its Selective Fluorescent Enhancement by Zinc and Aluminum Ions. International Journal of Organic Chemistry.
[24]
Qiao, Y.L., Zhang, J., Xu, W. and Zhu, D.B. (2011) Novel 2,7-Substituted Pyrene Derivatives: Syntheses, Solid-State Structures, and Properties. Tetrahedron, 67, 3395-3405. https://doi.org/10.1016/j.tet.2011.03.055
[25]
Rathfon, J.M., AL-Badri, Z.M., Shunmugam, R., Berry, S.M., Pabba, S., Keynton, R.S., Cohn, R.W. and Tew, G.N. (2009) Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub-Micrometer Fibers. Advanced Functional Materials, 19, 689-695. https://doi.org/10.1002/adfm.200800947
[26]
Ou, C.J., Lei, Z.F., Sun, M.L., Xie, L.H., Qian, Y., Zhang, X.W. and Huang, W. (2015) Dumbbell Effects of Solution-Processed Pyrene-Based Organic Semiconductors on Electronic Structure, Morphology and Electroluminescence. Synthetic Metals, 200, 135-142. https://doi.org/10.1016/j.synthmet.2014.12.034
[27]
Hsieh, W.H., Wan, C.F., Liao, D.J. and Wu, A.T. (2012) A Turn-On Schiff Base Flu-Orescence Sensor for Zinc Ion. Tetrahedron Letters, 53, 5848-5851.
https://doi.org/10.1016/j.tetlet.2012.08.058
[28]
Chercka, D., Yoo, S.J., Baumgarten, M., Kim, J.J. and Mullen, K. (2014) Pyrene Based Materials for Exceptionally Deep Blue OLEDs. Journal of Materials Chemistry C, 2, 9083-9086. https://doi.org/10.1039/C4TC01801J
[29]
Wang, B.C., Chang, J.C., Tso, H.C., Hsu, H.F. and Cheng, C.Y. (2003) Theoretical Investigation the Electroluminescence Characteristics of Pyrene and Its Derivatives. Journal of Molecular Structure: THEOCHEM, 629, 11-20.
https://doi.org/10.1016/S0166-1280(02)00787-X
[30]
Malliaras, G.G. and Scott, J.C. (1998) The Roles of Injection and Mobility in Organic Light Emitting Diodes. Journal of Applied Physics, 83, 5399-5403.
https://doi.org/10.1063/1.367369
[31]
Liao, C.T., Chen, H.F., Su, H.C. and Wong, K.T. (2011) Tailoring Balance of Carrier Mobilities in Solid-State Light-Emitting Electrochemical Cells by Doping a Carrier Trapper to Enhance Device Efficiencies. Journal of Materials Chemistry, 21, 17855-17862. https://doi.org/10.1039/c1jm13245h
[32]
Lee, S.E., Lee, H.W., Lee, J.W., Hwang, K.M., Park, S.N., Yoon, S.S. and Kim, Y.K. (2015) Optimization of Hybrid Blue Organic Light-Emitting Diodes Based on Singlet and Triplet Exciton Diffusion Length. Japanese Journal of Applied Physics, 54, Article ID: 06FG09. https://doi.org/10.7567/JJAP.54.06FG09