Traps and performance of MEH-PPV/CdSe(ZnS) nanocomposite-based organic light-emitting diodes

Abstract

We report the fabrication and investigations of organic light-emitting diodes (OLEDs) using a composite made by mixing poly[2-methoxy-5(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with CdSe/ZnS core/shell quantum dots (QDs). The electroluminescence efficiency of the studied devices was found to be improved as compared to devices using MEH-PPV. Moreover, the current density decreased with increasing QD concentration. We checked the effects of QDs on the electrical transport by determining the trap states, making use of the charge-based deep level transient spectroscopy (Q-DLTS) technique. The most striking result obtained is the decrease in trap density when adding QDs to the MEH-PPV polymer film. These results suggest that QDs would heal defects in nanocomposite-based devices and that CdSe/ZnS QDs prevent the trap center formation.

The role of defects in organic image sensors for green photodiode

“…To elucidate the mechanism of enhanced EQE characteristic by the P-doping of SiO x N y buffer layer, we performed the charge based deep level transient spectroscopy (Q-DLTS) measurements for the two OPD samples, in which the temperature is kept constant while the frequency is scanned. This method has been particularly successful to measure the current transient for organic materials 23–25 .…”

Efficiency enhancement in a single emission layer yellow organic light emitting device: Contribution of CIS/ZnS quantum dot

“…Although CIS/ZnS presented a PL, using bare CIS/ZnS as the active layer in the studied device structure gave no EL at all. This situation may be explained by i) the defects of QD [42] and ii) the insulator effect of ligand myristic acid that contains an alkyl chain of 14C. Incorporation of 0.4 wt.% CIS/ZnS in the polymer, significantly improved the device performance.…”

Morphology Control in Biphasic Hybrid Systems of Semiconducting Materials

“…Most studies use poly( N ‐vinylcarbazole) (PVK) as the semiconducting polymer matrix, and the combined simultaneous emission of organic and inorganic components is investigated . However, there are examples where QDs imbedded in the MEH‐PPV matrix do not contribute to the electroluminescent profile but are responsible for the improved electroluminescence efficiency compared to devices fabricated using pure MEH‐PPV as the active layer . Moreover, it was shown that once polymer/QD nanocomposites with polymers chemically grafted to the QDs are used, the device performance is even further improved compared to physically mixed blends .…”