Single-layer organic light-emitting diodes using naphthyl diamine

Abstract

N , N ′ -diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′diamine (NPB), a common hole transporter, was employed to fabricate single-layer organic light-emitting diodes (OLEDs). With a quasi-Ohmic anode, NPB device exhibited a bulk-limited hole current in the low-voltage region. Electron injection and light emission were clearly observed for applied voltages exceeding 4V. In order to confine the recombination zone, intentional doping was applied to the single-layer device. After doping with perylene, the luminance and current efficiency of NPB device increased dramatically. It is expected that more efficient single-layer OLEDs can be achieved by using the doping strategy.

Heavily Doped, Charge-Balanced Fluorescent Organic Light-Emitting Diodes from Direct Charge Trapping of Dopants in Emission Layer

“…This demand is attributed to the benefits of the simple device structure, the exclusion of the costly phosphorescent dopants, and a relatively low fabrication cost. [7][8][9][10][11][12] Low doping concentration is generally used to obtain the high efficiency of these devices because its additional loading of dopants gives rise to heavier self-quenching. 10 tandem FLOLEDs.…”

“…14 From those approaches, as well as other research reports, the highest current efficiencies were obtained by enhancing Fӧrster energy transfer with low doping concentration of C545T in Alq 3 host [13][14][15][16] and/or by increasing the hole current density via electrode modification. [8][9][10][11] Generally, 4~5% doping in EML has been widely investigated in the case of phosphorescent OLEDs (PHOLEDs) through long range dexter energy transfer compared to low doping (less than 1%) of FLOEDs with short-range Fӧrster energy transfer by dipole-dipole interaction. In the ideal case, host-guest energy transfer with 1% dopant concentration in PHOLEDs was unusually observed due to the combination of efficient Fӧrster energy transfer 1 and dexter energy transfer between host singlet and the metal-to ligand charge-transfer (MLCT) state.…”

The synthesis, characterization and electroluminescent properties of zinc(II) complexes for single-layer organic light-emitting diodes

“…The results show that PL peaks were slightly redshifted from 468 nm to 484 nm for ligand 8 and from 469 nm to 486 nm for ligand 9, respectively with the increase in solvent polarity. It is proved that the Stokes shift is in direct proportion with the solvent polarity [30]. It is believed that the scale of solvent polarizability parameter, which measures the ability of the medium to stabilize the charge on a dipole by virtue of its dielectric effects [33].…”

“…Low electroluminescence (LE) efficiency in some OLEDs is attributed mainly to an imbalance in the transportation rates of holes and electrons in the LE layer [23,24]. To balance the transport rates and improve the device performance of OLEDs, incorporating electron-and hole-transport units into the molecular structure of emitting materials is one of the commonly used strategy for chemical modification [25][26][27][28][29][30][31]. It is conceivable that the overall cost will be reduced by a more simplified device fabrication.…”

High Efficiency Red Phosphorescent Organic Light-Emitting Diodes with Simple Structure

“…Furthermore, bilayered devices consisting of an organic single layer with a buffer layer on the electrode have also been reported without any significant improvement of the device performances (Q. Gao et al, 2003;Wang et al, 2006;Tse et al, 2007). However, truly organic single layered approach is almost rare.…”