111 119 111 Bulletin of the College of Engineering, N.T.U., No. 89, October 003, pp. 111 119 MEH-PV DPO-PV CHAIN COMPOSITION DEPENDENCE OF OPTOELECTRONIC PROPERTIES FOR MEH-PV/DPO-PV COPOLYMERS * ** Hsuan-Liang Chou King-Fu Lin Yu-Kai Han Ding-Chang Wang * ** PLED * ** * Ph.D. student ** Professor Project Manager President & CEO * ** Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C. Ritdisplay Corporation, No.1, Kuanfu N. Road, Hsin Chu Industrial Park, Taiwan 30316, R.O.C. Abstract The copolymerization of 5-methoxy--(( -ethyl- hexyl) -oxy)-p-phenylenevinylene (MEH-PV) and,3-diphenyl- 5-octyl-1,4-phenylenevinylene (DPO-PV) via the Gilch route tended to form an alternative copolymer. As a result, the emission color of electroluminescence (EL) of MEH-PPV could be adjusted from orange-red to blue-green by copolymerization. However, the turn-on voltage of the prepared light emitting diode device was increased and the EL efficiency was decreased with the content of DPO-PV in copolymer. Keywords: Optoelectronic polymers, copolymers, PLED, optoelectronic properties. 5-methoxy--(( -ethyl-hexyl)-oxy)-p-phenylenevinylene (MEH-PV),3-di-phenyl-5-octyl-p-phenylenevinylene (DPO-PV) Gilch MEH-PPV (EL) DPO-PV 1. (OEL) 1960 anthracene 400V [1] 1987 Tang Vanslyke [] OEL 1% 1000cd/m (PLED) 1990 Bradley [3] Poly (p-phenylene vinylene) (PPV) ITO/PPV/Al PLED 0.05% PPV (EL) (1) [4,5] () [6,7] (3) [8~10] PLED [11,1] PPV Poly[(5-methoxy-- ( -ethyl-hexyl)-oxy)-p-phenylenevinylene] (MEH-PPV) [13~15] MEH-PPV Hsieh [16] Poly-(,3-diphenyl-5-octyl-pphenylenevinylene ) (DPO-PPV) [17] Chloro Precursor Route (CPR) DPO-PPV MEH-PPV CPR
11 NMR MEH-PV/DPO-PV 1 [18] [19] MEH-PPV DPO-PPV 1 F1 ) / F1 (1 f1) = r1 [ f1 ( F1 1) / F1 (1 f1) ] f (1 + r (1) f 1 f MEH-PPV DPO-PPV F 1 F MEH-PV DPO-PV r 1 = k 11 /k 1 r = k /k 1 k 11 MEH-PV MEH-PPV k 1 MEH- PV DPO-PPV MEH-PV/DPO-PV (1) r 1 0.168 r 0.190 [18] r 1 r 1 MEH-PV/DPO-PV (alternative) PLED MEH-PV.1..1.1 MEH-PPV ( 1 ) 9.3 4-methoxyphenol KOH 50 -ethylhexyl bromide 48 10 C/0.1torr 31.5 1-((-ethylhexyl)oxy)-4-methoxybenzene 57% 11.46 1-((-ethylhexyl)oxy)-4- methoxybenzene 45 (37%) 35 (39%) 60 dioxane 0 C 3 5 (39%) 0 C 3.5 1.8 1,4-bis(chloro- methyl)--((-ethyl-hexyl)oxy)-5-methoxy-bezene 79% OH OMe KOH + MeOH Fig. 1 1 MEH-PPV Synthesis scheme of MEH-PPV monomer.1. DPO-PPV ( ) 31.5 Diethyl 1,3-acetonedicarboxylate 36.3 Benzil 100 CH 3 OH 6 NaOH 30 CH 3 OH 4 6 5 51. EtO C O O Br NaOH MeOH,5-dicarbethoxy-3,4-diphenyl- cyclopentadienone (1) 78% 0,5-dicarbe- thoxy-3,4-diphenylcyclopentadienone 8.3 1- dectyne 150 benzene 4 ( = 8 1 ) 1.9 83% 15 diethyl,3-diphenyl-5-octyl terephthalate 100 1M LiAlH 4 THF 4 15 00 CHCl 3 ( = 6 1 ) 10 80% 8 diethyl,3-diphenyl-5-octyl 1,4-bis(hydroxymethyl) benzene + Ac O H SO 4 O CO Et + HC C
MEH-PV DPO-PV 113.1.3 MEH-PV/DPO-PV ( 3 ) 0.001 DPO-PPV 0.001 MEH- PPV 0. 4-tert-butylbenzyl chloride THF t-buok 0.1M 4 4 F 1 = 0.47 (f 1 = 0.5) DPO-PV/MEH-PV f 1 F 1. DPO-PPV Fig. Synthesis scheme of DPO-PPV monomer 與 80 毫升 dichloromethane 0 毫升 thionyl chloride 數滴 pyridine 混合後迴流加熱 4 小時, 真空濃縮, 以凝膠管柱層析分離 DPO-PPV 單體產物 ( 正己烷 : 乙酸乙酯 = 10:1 為沖提液 ), 得 6.6 克橘黃色黏稠液體, 產率 75.5% (UV-vis) JASCO-555 SPEX 1403 (Cyclic Voltammetry) Ag/AgCl (Pt) (counter electrode) 0.1M tetrabutylammonium tetrafluoroborate acetonitrile 30mV/s ferrocene/ferrocenium TA TGA 51 Thermogravimetric Analyzer 10 10 C/min (PANI) (α-step) ClH C t-buok O CH Cl + ClH C CH Cl MeO O Al Ca Polymer PANI Indium-tin-oxide glass THF OMe n 3 MEH-PV/DPO-PV Fig. 3 Copolymerization of MEH-PV/DPO-PV copolymer via the chloro precursor route (CPR) Fig. 4 light 4 PLED Schematic diagram of PLED device
114.3 PLED PLED 1. ITO ITO 0.5 wt% 0 O -plasma ITO ITO. MEH-PV/DPO-PV 0.5 wt% 0. 3. PLED PANI ITO ITO 7 10 6 torr 4. PLED UV PLED ITO UV PLED 4 3. Detect Response (mv) 5 Fig. 5 16 18 0 4 Elution time (min) MEH-PPV DPO-PPV MEH-PV/DPO- PV GPC ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 GPC plots of MEH-PPV, DPO-PPV and various MEH-PV/DPO-PV copolymers with ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1 1 CPR MEH-PPV/ DPO-PPV f 1 MEH-PPV MEH-PPV 5 MEH-PPV DPO-PPV GPC M n M w 1 MEH-PPV 64,000g/mol DPO-PPV 1,000g/mol MEH-PV/DPO-PV MEH-PPV DPO-PPV MEH-PV/DPO-PV [18] 1 MEH-PPV DPO-PPV MEH-PV/DPO- PV [18] Table 1 Data of MEH-PPV, DPO-PPV and MEH- PV/DPO-PV copolymers [18] f 1 F 1 M n, g/mol M w, g/mol Mm Mn 0 0 1,000 83,000 3.90 0.14 0. 148,000 311,000.11 0.5 0.43 15,000 544,000 4.35 0.50 0.47 18,000 701,000 5.49 0.75 0.6 8,000 348,000 4. 0.86 0.66 174,000 8,000 4.73 1 1 64,000 66,000 4.13 3.1 MEH-PV UV 6 F 1 < 0.6 UV MEH-PV F 1 > 0.6 F 1 = 0.47 (f 1 = 0.5) UV F 1 = 0.6 [18] π (delocalization) MEH-PV MEH-PPV [0~] UV λ (µm) [3] E (ev), E = 140/ λ () 7 MEH-PV F 1 = 0.47 E =.16eV MEH-PPV.1eV
MEH-PV DPO-PV 115 Absorbance (a.u.) 6 Fig. 6 400 500 600 Wavelength(nm) MEH-PPV DPO-PPV MEH-PV/DPO- PV UV ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 UV-vis absorption spectra of MEH-PPV, DPO-PPV and various MEH-PV/DPO-PV copolymers in spin-cast films, with following composition ratios: ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1 MEH-PV/DPO-PV (CV) 8 CV ferrocene/ferrocenium (Fc/Fc + ) 0.47eV ( Ag ) ferrocene 4.8eV [4] 4.33 HOMO UV Energy gap LUMO ( HOMO Energy gap = LUMO) HOMO LUMO MEH-PV 9 MEH-PV HOMO LUMO LUMO CV 3. 10 PLED (PL) (EL) PL EL MEH-PV EL PL Energy gap(ev).7.6.5.4.3..1 0.0 0. 0.4 0.6 0.8 1.0 F 1 7 MEH-PPV DPO-PPV MEH-PV/DPO- PV MEH-PV (F 1 ) Fig. 7 Dependence of energy gap of MEH-PV/DPO- PV copolymers on the molar fraction of MEH-PV units, F 1 Current (ma) 8 Fig. 8 1 0-1 0.68-0.0 0. 0.4 0.6 0.8 1.0 Potential (V) MEH-PPV DPO-PPV MEH-PV/ DPO- PV CV ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 CV plots of MEH-PPV, DPO-PPV and various MEH-PV/DPO-PV copolymers with: ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1
116 Energy level(ev) 9 Fig. 9 6 5 4 3 HOMO LUMO 0.0 0. 0.4 0.6 0.8 1.0 F 1 MEH-PPV DPO-PPV MEH-PV/DPO- PV HOMO LUMO MEH-PV (F 1 ) Dependence of HOMO and LUMO of MEH- PV/DPO-PV copolymers on the molar fraction of MEH-PV units, F 1 (a) PL 475nm 600nm EL 485nm 610nm MEH-PV 60mol% MEH-PPV MEH-PPV DPO-PPV MEH-PV MEH-PPV DPO-PV MEH-PV 11 PLED (I) (V) MEH-PV 1 MEH-PPV 3V DPO-PPV 14V MEH-PV F 1 = 0.4 F 1 = 0.6 MEH-PPV PLED HOMO [5] MEH-PV F 1 = 0.4 [18] DPO-PV F 1 = 0.6 MEH-PV Intensity(a.u.) (b) 400 450 500 550 600 650 700 Wavelength(nm) 10 (a) MEH-PPV DPO-PPV MEH-PV/ DPO-PV PL (b) MEH-PPV DPO-PPV MEH-PV/DPO- PV EL ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 Fig. 10 (a) PL spectra of various MEH-PV/DPO-PV copolymers and (b) EL spectra of their PLED devices: ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1 Current density(a/cm ) 0.5 0.0 0.15 0.10 0.05 0.00 0 5 10 15 0 Voltage(V) 11 MEH-PPV DPO-PPV MEH-PV/DPO- Fig. 11 PV PLED I-V ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 I-V plots of various MEH-PV/DPO-PV PLED devices: ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1
MEH-PV DPO-PV 117 Threshold voltage (V) 16 14 1 10 8 6 4 0.0 0. 0.4 0.6 0.8 1.0 1 MEH-PPV DPO-PPV MEH-PV/ Fig. 1 F 1 DPO-PV PLED MEH-PV (F 1 ) Dependence of threshold voltage for MEH- PV/DPO-PV PLED devices on the molar fraction of MEH-PV units, F 1 13 PLED (L) (V) MEH-PPV 14V 180cd/m 0.87A/cm DPO-PPV 14V 11.cd/m 0.11A/cm 15V MEH-PPV DPO-PV MEH-PPV 370 C DPO-PV DPO-PPV 450 C [18] 4. CPR MEH-PV/DPO-PV MEH-PPV MEH-PV UV PL, HOMO LUMO PLED EL PL 5nm ~ 10nm MEH-PV Brightness(Cd/m ) 100 10 1 0 5 10 15 0 Voltage(V) 13 MEH-PPV DPO-PPV MEH-PV/ DPO- PV PLED L-V ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 ( ) F 1 = 1 Fig. 13 L-V plots of various MEH-PV/DPO-PV PLED devices: ( ) F 1 = 0 ( ) F 1 = 0. ( ) F 1 = 0.43 ( ) F 1 = 0.47 ( ) F 1 = 0.6 ( ) F 1 = 0.66 and ( ) F 1 = 1 14V 3V NSC91-16- E-00-004 [1] M. Pope, H. P. Kallmann and P. Magnante, Electroluminescence in organic crystals, J. Chem. Phys., Vol. 38, 1963, p. 04. [] C. W. Tang and S. A. Vanslyke, Organic electroluminescent diodes, Appl. Phys. Lett., Vol. 51, 1987, pp. 913 915. [3] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Bruns and A. B. Holmes, Light-emitting diodes based on conjugated polymers, Nature, Vol. 347, 1990, pp. 539 540. [4] Y. Xiao, W. L. Yu, Z. K. Chen, N. H. S. Lee, Y. H. Lai and W. Huang, Synthesis and characterization of a novel light-emitting copolymer with improved charge-balancing property, Thin Solid Films, Vol. 363, 000, pp. 10 105.
118 [5] J. Morgado, F. Cacialli, R. H. Friend, B. S. Chuah, H. Rost and A. B. Holmes, Light-emitting devices based on a poly(p-phenylene vinylene) statistical copolymer with oligo(ethylene oxide) side groups, Macromolecules, Vol. 34, 001, pp. 3094 3099. [6] J. A. Osaheni and S. A. Jenekhe, New red lightemitting conjugated rigid-rod polymer: poly (benzobisthiazole-1,4-phenylenebisvinylene), Macromolecules, Vol. 6, 1993, pp. 476 478. [7] C. J. Brabec, V. Dyakonov, N. S. Sariciftci, W. Graupner, G. Leising and J. C. Hummelen, Investigation of photoexcitations of conjugated polymer/fullerene composites embedded in conventional polymers, J. Chem. Phys., Vol. 109, 1998, pp. 1185 1196. [8] F. Cacialli, R. H. Friend, N. Haylett, R. Daik, W. J. Feast, D. A. Dos Santos and J. L. Bredas, Efficient green light-emitting diodes from a phenylated derivative of poly(p-phenylene vinylene), Appl. Phys. Lett., Vol. 69, 1996, pp. 3794 3796. [9] M. Hamaguchi and K. Yoshino, Color-variable electroluminescence from multilayer polymer films, Appl. Phys. Lett., Vol. 69, 1996, pp. 143 145. [10] J. I. Jin, J. C. Kim and H. K. Shim, Synthesis and electrical properties of poly(-bromo-5-methoxy- 1,4-phenylenevinylene) and copolymer, Macromolecules, Vol. 5, 199, pp. 5519 553. [11] D. Braun and A. J. Heeger, Visible light emission from semiconducting polymer diodes, Appl. Phys. Lett., Vol. 58, 1991, pp. 198 1984. [1] R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Brédas, M. Lögdlund and W. R. Salaneck, Electroluminescence in conjugated polymers, Nature, Vol. 397, 1999, pp. 11 18. [13] Y. Xiao, W. L. Yu, J. Pei, Z. Chen, W. Huang and A. J. Heeger, Conjugated copolymers of - methoxy-5- -ethyl-hexyloxy-1,4-phenylenevinylene and,5-dicyano-1,4-phenylenevinylene as material for polymer light-emitting diodes, Synth. Met., Vol. 106, 1999, pp. 165 170. [14] B. H. Sohn, K. Kim, D. S. Choi, Y. K. Kim., S. C. Jeoung and J.-I. Jin, Synthesis and luminescence properties of poly[-(9,9-dihexylfluorene--yl)-1,4- pheny-lenevinylene] and its copolymers containing -( -ethylhexyloxy)5-methoxy-1,4-phenylenevinyle ne units, Macromolecules, Vol. 35, 00, pp. 876 881. [15] T. W. Lee, O. O. Park, H. N. Cho, J. M. Hong, C. Y. Kim and Y. C. Kim, White emission from a ternary polymer blend by incomplete cascade energy transfer, Synth. Met., Vol. 1, 001, pp. 437 441. [16] W. C. Wan, H. Antoniadis, V. E. Choong, H. Razafitrimo, Y. Gao, W. A. Feld, B. R. Hsieh, Halogen precursor route to poly[(,3-diphenyl-pphenylene)vinylene] (DP-PPV): synthesis, photoluminescence, electroluminescence, and photoconductivity, Macromolecules, Vol. 30, 1997, pp. 6567 6574. [17] PPV 00 [18] C. C. Chiu, K. F. Lin and H. L. Chou, Chain composition dependence of luminescence properties for copolymers of -methoxy-5--ethyl-hexyloxy- 1,4-phenylenevinylene and,3-diphenyl-5-octyl- 1,4-phenylenevinylene, J. Poly. Sci., Polym. Chem. Ed., Vol. 41, 003, pp. 180 186. [19] G. Odian, Principles of Polymerization, Chapter 6, 3rd Ed.; John Wiley & Sons, New York, 1990, pp. 45 531. [0] M. Yan, L. J. Rotherberg, F. Papadimitrakopoulos, M. E. Galvin and T. M. Miller, Spatially indirect excitons as primary photoexcitations in conjugated polymers, Phys. Rev. Lett., Vol. 7, 1994, pp. 1104 1107. [1] Y. Shi, J. Liu and Y. Yang, Device performance and polymer morphology in polymer light emitting diodes: the control of thin film morphology and device quantum efficiency, J. Appl. Phys., Vol. 87, 000, pp. 454 463. [] T. Q. Nguyen, I. B. Martini, J. Liu and B. J. Schwartz, Controlling interchain interactions in conjugated polymers: the effects of chain morphology on exciton-exciton annihilation and aggregation in MEH-PPV films, J. Phys. Chem. B, Vol. 104, 000, pp. 37 55. [3] L. H. Wang, Z. K. Chen, E. T. Kang, H. Meng and W. Huang, Synthesis, spectroscopy and electrochemistry study on a novel di-silyl substituted poly(p-phenylene vinylene), Synth. Met., Vol. 105, 1999, pp. 85 89. [4] H. L. Cheng and K. F. Lin, Structural characterization and luminescent properties of poly (p-phenylene vinylene) and poly(ethylene glycol) blends, J. Polym. Res., Vol. 6, 1999, pp. 13 131. [5] I. D. Parker, Carrier tunneling and device characteristics in polymer light-emitting diodes, J. Appl. Phys., Vol. 75, 1994, pp. 1656 1666.
MEH-PV DPO-PV 119 (Hsuan-Ling Chou) 64 89 (King-Fu Lin) 41 77 84 Farboil 85 90 (Yu-Kai Han) 80 8 83 87 87 89 89 PLED (Ding-Chang Wang) 43 69 89 USIFE-CGPC Group 89 90 EMBA 9 8 0 9 9 9 9 10 1 Manuscript received August 0, 003, revised September 9, 003, accepted October 1, 003