Supplemental Material
Charge transport, carrier balance and blue electrophosphorescence
in
diphenyl(4-(triphenylsilyl)phenyl)phosphine
oxide
(EMPA
1)
devices
Masashi Mamada, Selin Ergun, César Pérez-Bolivar, and Pavel Anzenbacher, Jr.*
Center for Photochemical Sciences, Bowling Green State University, Bowling Green,
Ohio 43403, USA
Charge transport, carrier balance and blue electrophosphorescence in diphenyl(4-(triphenylsilyl)phenyl)phosphine oxide
(EMPA 1) devicesSupplemental Material
Contents
1. Instruments
2. Materials
3. OLED Fabrication and Measurement
4. UV-vis and PL spectra
5. Energy level diagram for Devices V and VI
6. I-V and L-V curves for Devices V and VI
7. Reference
1. Instruments
Mass spectra were collected on Shimadzu Gas Chromatography – Mass Spectrometry (GC-MS)
QP5050A instrument equipped with a direct probe ionization. 1H-NMR and 13C-NMR spectra were
recorded on a 300 MHz Bruker or 500 MHz Bruker instrument. Chemical shifts were calibrated to
the corresponding deuterated solvents. Melting points were obtained on a Shimadzu DSC-60.
UV/VIS spectra were measured using Hitachi U-3010 double beam spectrophotometer, accurate to ±
0.3 nm. The light source consisted of Deuterium (D2) and Tungsten Iodide (50W) lamps for the
ultraviolet and visible regions respectively. Emission spectra were recorded using a
spectrofluorimeter from Edinburgh Analytical Instruments (FL/FS 900). Compounds were dissolved
in freshly distilled dichloromethane (DCM) prior to measurements. Cyclic voltammetry (CV) and
Differential Pulse Voltammetry (DPV) were carried out in nitrogen-purged dimethylformamide
(DMF) or DCM Electrochemical Workstation at room temperature. Tetrabutylammonium
perchlorate (TBAP) (0.1 M) in DMF or DCM was used as the supporting electrolyte. The
conventional three-electrode configuration consisted of a platinum working electrode, a platinum
wire auxiliary electrode, and an Ag/AgCl reference electrode. Each measurement was calibrated
using ferrocenium-ferrocene (Fc+/Fc) as a standard. Cyclic voltammograms were obtained at scan
rate of 100 mV s-1. The DFT calculations diphenyl-(4-(triphenylsilyl)phenyl)phosphine oxide
(EMPA1) were carried out at a level of B3LYP/6-31+G(d,p) in vacuum. The structures were
geometrically optimized using HF 6-31 G. All calculations were performed using Gaussian 03 in a
dedicated 8 nodes server.
2. Materials
Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was purchased from H.C.
Starck (Clevios P VP Al 4083). 4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (-NPD) and
N,N′-dicarbazolyl-3,5-benzene (mCP) were purchased from OChem Inc. Corporation and BOC
Sciences,
respectively.
4,4′,4′′-Tri(N-carbazolyl)triphenylamine
(TCTA)
and
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) were purchased from Sigma-Aldrich and Alfa
S2
Charge transport, carrier balance and blue electrophosphorescence in diphenyl(4-(triphenylsilyl)phenyl)phosphine oxide
(EMPA 1) devicesSupplemental Material
Aesar, respectively. Cesium Fluoride (CsF) and aluminum (Al) were purchased from Acros Organics
and Kurt J. Lesker Company, respectively. Bis-[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III)picolinate (FIrpic) was prepared according to the literature method.1 All the materials,
except PEDOT:PSS, were purified by train sublimation prior to OLED fabrication.
3. OLED Fabrication and Measurement
OLEDs were fabricated on glass-coated ITO substrates from Delta Technologies (100–150 nm thick,
R ~ 15–20 /square). The ITO-coated substrates were degreased by detergent and organic solvents
and then UV-ozone cleaned to increase the ITO work function. PEDOT:PSS was spin-coated over 1
× 1 in. ITO substrates at 3000 rpm for 15 s and 4000 rpm for 15 s, and baked at 140 °C for 10 min.
Organic layers were deposited at ~1 Å/s in a high-vacuum chamber (107 Torr, Angstrom
Engineering). The emissive layer was formed by co-deposition of the dopant and the host at ~0.5 Å/s.
The electron injection buffer layer CsF (1 nm) was deposited at ~0.5 Å/s. The cathode realized by
shadow mask deposition of aluminum (~1.5 Å/s) without breaking the vacuum. The cathode
thickness and pixel area is 100 nm with 0.04 cm2. The thicknesses of the organic and metallic layers
were measured in situ with a quartz crystal sensor. All the electrical and optical characterization of
the diodes was performed with an integrating sphere using Hamamatsu Photonic C9920-22 External
Quantum Efficiency Measurement System, a Keithley 2400 sourcemeter and a multichannel
analyzer PMA-12. All the characterization of the devices was performed inside a nitrogen-filled
glovebox.
4. UV-vis and PL spectra
absorbance
emission at RT
emission at 77K
1.0
0.8
0.15
0.6
0.10
0.4
0.05
0.00
250
0.2
300
350
400
450
Wavelength (nm)
Figure S1 UV-vis and PL spectra of EMPA1.
S3
0.0
500
Emission (a.u.)
Absorbance (a.u.)
0.20
Charge transport, carrier balance and blue electrophosphorescence in diphenyl(4-(triphenylsilyl)phenyl)phosphine oxide
(EMPA 1) devicesSupplemental Material
5. Energy level diagram for Devices V and VI
(a)
(b)
2.4
2.4
2.8
2.8
3.0
3.47
-NPD
ITO
CsF/Al
EMPA1/
FIrpic
5.2
PEDOT:PSS
- N P D
4.1
4.7
2.8
3.47
4.7
BCP
4.1
EMPA1 /
FIrpic
ITO 5.2
CsF/Al
E M P1A
P E D O T: P S S
5.4
5.4
6.15
6.15
6.5
6.9
6.9
6.9
Figure S3 Energy level diagram for Device (a) V and (b) VI.
6. I-V and L-V curves for Devices V and VI
2
10000
Device V
Device VI
Device V
Device VI
300
1000
200
100
2
100
Luminance (cd/m )
Current density (mA/cm )
400
10
0
0
2
4
6
8
10
12
Voltage (V)
Figure S4 Voltage–current density and voltage–luminance characteristics of the devices V and VI.
7. Reference
1S.Lamansky,
M. E. Thompson, V. Adamovich, P. I. Djurovich, C. Adachi, M. A. Baldo, S. R.
Forrest, and R. Kwong, U. S. Patent 20050214576 (2005).
S4