Spiro-Configured Bifluorenes: Highly Efficient Emitter for UV Organic Light-Emitting Device and Host Material for Red Electrophosphorescence

Transcription

1 Spiro-Configured Bifluorenes: Highly Efficient Emitter for UV Organic Light-Emitting Device and Host Material for Red Electrophosphorescence Ken-Tsung Wong,* a Yuan-Li Liao, a Yu-Ting Lin, b Hai-Ching Su, b Chung-chih Wu* b a Department of Chemistry, National Taiwan University, Taipei 106, Taiwan b Department of Electrical Engineering, Graduate Institute of Electro-optical Engineering and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 106, Taiwan Supporting Information Synthesis and characterization Preparation of 9,9 -spirobifluorene-configured bi(9,9-diarylfluorene)s by Suzuki coupling reaction: 2,2 -diiodo-9,9'-spirobifluorene (1.0 mmol), 2-(9,9-diarylfluorenyl) pinacol boronate (2.1 mmol), Pd(PPh 3 ) 4 (5mmol), potassium carbonate (2.0 mmol) and tri-tert-butylphosphine (0.10 mmol) were mixed in a flask containing with toluene (20 ml). The mixture was refluxed for 3 days. The solution was quenched with saturated sodium bicarbonate and extracted twice with chloroform. The combined organic extracts were dried (MgSO 4 ) and concentrated by rotary evaporation. Column chromatography on silica gel (hexane/chloroform = 4/1) afforded products as white solids. SSS: mp C; IR (neat) ν 3065, 3051, 2972, 1712, 1447, 1268 cm -1 ; 1 H NMR (CDCl 3, 400 MHz) δ 7.84 (d, J = 7.7 Hz, 4H), 7.78 (d, J = 7.6 Hz, 4H), 7.74 ~ 7.70 (m, 4H), 7.38 ~ 7.29 (m, 12H), 7.10 ~ 7.02 (m, 8H), 6.87 ~ 6.84 (m, 4H), 6.72 ~ 6.69 (m, 4H), 6.66 ~ 6.63 (m, 10H); 13 C NMR (CDCl 3, 100 MHz) δ 149.2, 149.1, 149.0, 148.9, 148.6, 141.7, 127.8, 127.7, 127.6, 127.1, 124.1, 123.9, 123.8, 122.6, 122.4, 119.9, 66.0, ; MS (m/z, FAB + ) 945 (40), 607 (25), 579 (10), 359 (5), 341 (100), 307 (40); Anal. Calcd. C, 95.31; H, 4.69, found C, 95.29; H, TST: mp C; IR (neat) ν 3065, 3025, 2925, 1679, 1507, 1460 cm -1 ; 1 H NMR (CDCl 3, 400 MHz) δ 7.85 ( d, J = 8.0 Hz, 4H), 7.69 (d, J = 7.3 Hz, 2H), 7.63 (d, J = 8.0 Hz, 2H), 7.53 (d, J = 8.0 Hz, 2H), 7.50 (s, 28H), 7.37 ~ 7.30 (m, 8H), 7.23 (t, J = 7.5 Hz, 2H), 7.10 ~ 7.06 (m, 10H), 7.00 ~ 6.96 (m, 10H), 6.73 (d, J = 7.5 Hz, 2H), 2.26 (s, 12H); 13 C NMR (CDCl 3, 100 MHz) δ 152.0, 151.8, 149.2, 149.1, 142.9, 141.3, 141.0, 140.5, 139.6, 139.2, 136.1, 128.9, 128.0, 127.8, 127.7, 127.6, 127.3, 127.1, 126.6, 126.0, 124.5, 124.0, 122.6, 120.2, 120.1, 12, 66.1, 64.9, 20.9.; MS (m/z, FAB + ) 1004 (35), 914 (70), 824 (50), 607 (20), 341 (100), 307 (90); Anal. Calcd. C, 94.39; H, 5.61, found C, 94.35; H, Photophysical Properties of Organic Thin Films: The photoluminescence (PL) quantum yields of organic thin films were determined using a calibrated

2 integrating sphere coupled to a CCD spectragraph. The 325-nm line of the He-Cd laser was used to excite samples placed in the calibrated integrating sphere. By comparing the spectral intensities of the excitation laser and the PL emission, the PL quantum yields of organic thin films were derived. The phosphorescence spectra of bifluorene films were measured at 77 K using a 5-ms delay time between the excitation with a microsecond flash lamp and the measurement. Device Fabrication: The device on the glass substrate has the structure of multiple organic layers sandwiched between the transparent bottom indium-tin-oxide (ITO) anode and the top metal cathode. The conducting polymer PEDT:PSS was prepared by spin coating, and other material layers were deposited by thermal evaporation in a vacuum chamber with a base pressure of <10-6 Torr. All organic compounds of small molecular weight were purified by sublimation before use. Device Characterization: The current-voltage-brightness (I-V-L) characterization of the light-emitting devices was performed with a source-measurement unit and a Si photodiode calibrated with the Photo Research PR650 spectroradiometer. The electroluminescence (EL) spectra of devices were collected by a CCD spectragraph.

3 SSS TST Potential (V vs Fc/Fc + ) Figure S-1: Cyclic voltammograms (CV) of SSS and TST. For this work, CVs were performed at a scan rate of 100 mv/s using the glass electrode as the working electrode and Ag + /AgCl as a reference electrode. Reduction CV was performed in THF with 0.1 M of nbu 4 ClO 4 as a supporting electrolyte, in which the internal standard, ferrocene/ferrocenium ion (Fc/Fc + ) redox couple, shows E 1/2 = 0.65 V. Oxidation CV was performed in CH 2 Cl 2 with 0.1 M of nbu 4 NPF 6 as a supporting electrolyte, in which Fc/Fc + redox couple gives E 1/2 = 0.51 V. The potential value was recorded relative to the oxidation potential of ferrocene, which was added to the electrolyte as an internal standard.

4 Normalized Intensity (a.u.) 1.0 Absorption SSS (solution) B2 (solution) 0.8 SSS (film) B2 (film) Fluorescence 0.6 SSS (solution) B2 (solution) SSS (film) 0.4 B2 (film) Wavelength (nm) Figure S-2: Absorption and fluorescence spectra of SSS and B2 in solutions and in thin films. Normalized Intensity (a.u.) 1.0 Absorption TST (solution) T2 (solution) 0.8 TST (film) T2 (film) Fluorescence 0.6 TST (solution) T2 (solution) 0.4 TST (film) T2 (film) Wavelength (nm) Figure S-3: Absorption and fluorescence spectra of TST and T2 in solutions and in thin films.

5 Quantum Efficiency (%) Current Density (ma/cm 2 ) Figure S-4: External quantum efficiency vs. current density for UV devices of ITO/PEDT:PSS (300 Å)/TCTA (400 Å)/SSS (device A) or TST (devise B) (300 Å)/TPBI (300 Å)/ LiF (5 Å)/Al. Current Density (ma/cm 2 ) Current Density Brightness Voltage (V) Brightness (cd/m 2 ) Figure S-5: I-V-L characteristics of UV devices of ITO/PEDT:PSS (300 Å)/TCTA (400 Å)/SSS (device A) or TST (devise B) (300 Å)/TPBI (300 Å)/ LiF (5 Å)/Al.