Unipolar space-charge limited current through layers with a disparate concentration of shallow traps: Experiment and model

Abstract

Interpretation of trap-limited mobility in space-charge limited current in organic layers with exponential density of traps J. Appl. Phys. 110, 043705 (2011); 10.1063/1.3622615 Space-charge limited conduction in doped polypyrrole devices J. Appl. Phys. 107, 093716 (2010); 10.1063/1.3373393Field-dependent mobility from space-charge-limited current-voltage curvesThe influence of the spatial distribution of trap states on unipolar space-charge limited current ͑SCLC͒ is investigated experimentally and theoretically. Thin-layered films of the small molecule organic semiconductor N , NЈ-di͑1-naphtyl͒-N,NЈ-diphenylbenzidine ͑␣-NPD͒ are vapor deposited on indium tin oxide, with aluminum as the counter electrode. The small molecule 4,4Ј ,4Љ-tris-͓N-͑1-naphtyl͒-N-͑phenylamino͔͒-triphenylamine ͑1-NaphDATA͒, which creates well-known shallow traps for holes, is used as dopant. The realized organic films consist of three layers, one of which is homogeneously doped. The influence of the spatial position of the doped layer on the current-voltage characteristics of the diodes is examined. Compared to an undoped device, the current density is strongly decreased and varies over orders of magnitude for the different spatial positions of the doped layer. It is shown that traps near the injecting electrode have the most pronounced effect on SCLC. A model for unipolar SCLC through a system of homogeneous layers with different trapping parameters for shallow traps is presented. The model quantitatively describes the experimental data and is used to calculate the spatial distributions of the charge-carrier density and the electric-field strength in the differently doped devices.

Intersystem Crossing and Triplet Fusion in Singlet-Fission-Dominated Rubrene-Based OLEDs Under High Bias Current

“…As can be seen, it includes three distinct regimes: (1) Ohmic, (2) trap-filled space charge limited current (TF-SCLC), and (3) trap-filled limit current (TFL-SCLC) regimes. 31,32 This indicated that traps which inevitably formed during device fabrication process existed at low injection current but some new traps were formed at higher injection currents. According to the reports in the literatures, the amounts of traps can increase with decreasing temperature, 29 and physical defects of the devices reduce the free triplet lifetime and can also reduce the intensity of delayed fluorescence by immobilizing the triplet excitons.…”

Trap-controlled hole transport in small molecule organic semiconductors

“…7 This renders ␣-NPD doped with 1-NaphDATA a good model system for investigating the effect of hole traps on hole charge transport. 8 Few microns of the organic semiconductors are deposited by thermal coevaporation at a base pressure of 10 −6 mbar onto a 10-nm-thick semitransparent Al electrode on a glass substrate and are topped with a thick Al counter electrode. The time-of-flight measurements 9 are carried out utilizing a frequency-tripled Nd:YAG ͑yttrium aluminum garnet͒ laser ͑Solar Systems LQ129/LQ103͒ at a wavelength of 355 nm and a pulse length of 10 ns, which is used to excite an electrode-near regime of the organic layer through the semitransparent Al electrode.…”

Non-switching to switching transferring mechanism investigation for Ag/SiOx/p-Si structure with SiOxdeposited by HWCVD

“…With increasing the positive applied voltage, electrons are injected into SiO x from the surface inversion layer of p-Si substrate, which will fill the discrete energy levels in band gap of SiO x to form a certain space charge distribution, which will be responsible for the trap-filled-limited SCLC (TFL-SCLC) [29,30]. Based on the Poisson's equation and current continuity equation, for single trap level, the TFL-SCLC is proportional to the square of voltage, i.e.…”