Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- Confocal scanning raman spectroscopy (CSRS) of an operating organic light-emitting diodePublication . Paez-Sierra, B. A.; Gomes, Henrique L.Organic molecules with semiconducting properties are becoming nowadays core of the organic-based electronic era. Although organic light emitting diodes (OLEDs) have already matured for commercial applications, they still require longer device lifetimes. Some of the long-standing challenges in OLED technology relay on degradation and failure mechanisms. Several authors observed that degradation and subsequent damage of OLEDs is accompanied by formation of dark non-emissive spots [1-2]. Implementation of the confocal scanning Raman spectroscopy (CSRS) measurements helps to understand the chemistry, physics of OLEDs and moreover to have better confidence on their quality assurance.
- Doping distribution of an operating organic light-emitting diode: a raman map analysisPublication . Paez-Sierra, B. A.; Gomes, Henrique L.; Rangel-Kuoppa, V.T.We present confocal Raman spectroscopy (CSRS) maps of Poly(9,9-dioctylfluorene) (PFO)-based organic light emitting diode under operation. The CSRS analysis of the OLEDs was performed in normal room conditions. The non-emissive spots presented higher Raman intensity and broadening of the vibrational bands in comparison with the luminescent ones. The phenomenon is associated with an increase in the PFO - * absorption band and hence modification of the PFO doping which becomes favorable to the excitation wavelength, thus the Raman spectrum is enhanced. To the authors’ knowledge this image technique had been missed for the OLED technology.
- The role of the electrode configuration on the electrical properties of small-molecule semiconductor thin-filmsPublication . Merces, Leandro; de Oliveira, Rafael Furlan; Gomes, Henrique L.; Bof Bufon, Carlos CesarThis paper presents a systematic analysis of the electrode configuration influence on the electrical properties of organic semiconductor (OSC) thin-film devices. We have fabricated and electrically characterized a set of planar two-terminal devices. The differences in I-V characteristics between the top and bottom contact structures are presented and analyzed. Top-contact configurations have a linear current vs. electric field behavior, while the bottom-electrode devices display a transition from ohmic to spacecharge-limited conduction regime. The transition is temperature-and thickness-dependent. Finite-element calculations show that when the OSC film is connected using top electrodes, the current flows through the OSC bulk region. On the other hand, the bottom-electrode configuration allows most of the current to flow near the OSC/substrate interface. The current probes interfacial states resulting in a space-charge conduction regime. The results shed some light on the so-called "contact effects" commonly observed in organic thin-film transistors. The findings presented here have implications for both the understanding of the charge transport in OSC films and the design of organic semiconductor devices. (C) 2017 Elsevier B.V. All rights reserved.