Electroluminescence enhancement in ultraviolet organic light‐emitting diode with graded hole‐injection and ‐transporting structure

Abstract

Electroluminescent intensity and external quantum efficiency (EQE) in ultraviolet organic light‐emitting diodes (UV OLEDs) have been remarkably enhanced by using a graded hole‐injection and ‐transporting (HIT) structure of MoO3/N,N ′‐bis(naphthalen‐1‐yl)‐N,N ′‐bis(phenyl)‐benzidine/MoO3/4,4′‐bis(carbazol‐9‐yl)biphenyl (CBP). The graded‐HIT based UV OLED shows superior short‐wavelength emis‐ sion with spectral peak of ∼410 nm, maximum electroluminescent intensity of 2.2 mW/cm2 at 215 mA/cm2 and an EQE of 0.72% at 5.5 mA/cm2. Impedance spectroscopy is employed to clarify the enhanced hole‐injection and ‐transporting capacity of the graded‐HIT structure. Our results provide a simple and effective approach for constructing efficient UV OLEDs. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Sb2O3/Ag/Sb2O3 Multilayer Transparent Conducting Films For Ultraviolet Organic Light-emitting Diode

“…5b). Owing to the high work function that matches the energy level better, and the lower sheet resistance, the turn on and operation voltage are relative lower compare to the reported results26. The output power and EL spectra were measured by PM310E (thorlabs), Avantes fiber spectrometer.…”

Vibrational mode contribution to the dielectric permittivity of disordered small-molecule organic semiconductors

“…For many small-molecule organic semiconductor materials, the dielectric permittivity at optical frequencies is known from thin-film ellipsometry measurements [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], electron energy loss spectroscopy [27], and from theory using quantum-chemically calculated molecular polarizabilities and the Clausius-Mossotti relationship [28,29]. The relative dielectric constant at quasistatic conditions may be obtained from low-frequency capacitance-voltage (C-V) studies of sandwich-type devices [30][31][32][33][34][35][36][37][38][39]. In principle, the dielectric permittivity in the full frequency range of interest can be obtained by combining the results of f -dependent C-V measurements (dielectric spectroscopy [40]), terahertz, infrared, and optical spectroscopy measurements.…”

The Optimization of Hole Injection Layer in Organic Light-Emitting Diodes

“…These structures can intuitively display the above theories, such as the devices with hole injection layers of Ag 2 O/MoO x , MoO 3 /NPB/MoO 3 /CBP, as even the concentration gradient provided a stepped energy level, which greatly facilitated hole injection and, hence, enhanced the injection current [ 89 , 90 , 91 ]. It has been reported that the presence of charge transfer between MoO 3 and NPB is also conductive to hole injection [ 92 , 93 ].…”