We report the results of measurements of traps in light emitting devices using a new derivative of poly(phenylene vi-nylene) (PPV) as an active material by the charge based Deep Level Transient Spectroscopy (Q-DLTS) technique. Diodes of structure Indium Tin Oxide (ITO)/PEDOT:PSS/poly(2-ethylhexyl)surfanyl-5- methoxy phenylene vinylene (MEH-S-PPV)/M with M = Al and M = Ca/Al were investigated by measurements of current-voltage-luminance characteristics. From analysis of these characteristics, evidence of charge trapping in devices was demonstrated. The trap parameters were then determined from Q-DLTS measurements, which were carried out on the samples as a function of the charging time, the applied voltage and the temperature. Five trap levels of activation energy in the range [0.3-0.6 eV] and of density of order of 1017 cm -3 were identified in diodes with Ca/Al cathode. Electron (one level) and hole (four levels) traps were then clearly distinguished by performing measurements in hole-only devices. Trapping processes are discussed and tentatively proposed to performance of the light emitting diodes studied.
|Number of pages||6|
|Journal||Physica Status Solidi (C) Current Topics in Solid State Physics|
|State||Published - 1 Jan 2009|
|Event||International Conference on Extended Defects in Semiconductors, EDS 2008 - Poitiers, France|
Duration: 14 Sep 2008 → 19 Sep 2008