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shows the energy diagram of α-NPD/ Alq3 based OLED. When the bare ITO and Al are used as an anode and a cathode respectively, the large barriers for the carrier injection exist in both two interfaces. On the other hand, when the ITO/ FSAM and LiF/Al are used as an anode and a cathode respectively, there is no barrier in both two interfaces.
Source publication
We propose the evaluation approach of the electron current in the bilayer organic light-emitting diode (OLED) using its device current and the hole current of hole transport material. The conduction current whose 50 nm-thick diamine derivative (α-NPD) layer is deposited on a fluorinated self-assembled monolayer (FSAM)-modified indium-tin-oxide (ITO...
Citations
There are many reports on thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) with the external quantum efficiency achieving 30%. We investigate the electrical conduction of 4CzIPN-based TADF OLEDs depending on doping concentration of 0, 10, 20 or 35 mol%. As the doping concentration of 4CzIPN is increased, the electrons injected into the 4CzIPN sites are easily hopping between the 4CzIPN sites. The drive voltage decreases but the power efficiency is not remarkably improved. Since the red-shift of EL spectra at a constant current density is observed with doping concentration, the main carrier recombination zone is found to move with doping concentration.
We studied the electrical conductivity of a bilayer specimen of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (α-NPD) and 1,3-bis(N-carbazolyl) benzene (mCP). The conductivity of indium tin oxide ITO/(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (FSAM)/α-NPD(50 nm)/Al can be explained by the space-charge-limited current (SCLC) model. In an α-NPD(50 nm)/mCP(10 nm) specimen, the current is similar to that in an α-NPD(50 nm) specimen despite the existence of a hole barrier between the α-NPD and mCP. The current in an α-NPD/mCP specimen is also proportional to the square of the voltage. We propose a conduction model that combines SCLC in the α-NPD layer and tunneling in the mCP layer.
This work reports a highly sensitive self-powered ultraviolet photodetector, which is based on the active layer of NPD:Alq3 with different Alq3 contents. All solution-processed technique was utilized to fabricate the active layers of the devices to achieve an optimized system that exhibits highly sensitive and stable photodetector under self-powered operation mode. The values of photosensitivity, responsivity, and detectivity of the photodiodes at zero-bias were estimated at 1.30 × 10⁵, 1.07 mA/W, 1.04 × 10¹¹ Jones, respectively. The rise and decay times of the optimized device were estimated at 0.34 s and 0.28 s, respectively. For practical application of the device sensing efficiency, the optimal load line of self-powered UV photodetector to deliver the maximum power was estimated of an internal impedence of 0.579 MΩ. In conclusion, the high sensitivity, good stability, and fast response/recovery speed of the self-powered UV photodetector make the devices applicable to resolve some of the current issues in UV detection.
