Influence of the organic hole transport layer on the dynamics of quantum dot-based light-emitting diodes

Colloidal quantum dots (QDs) have attracted considerable interest because of their unique properties, like high quantum efficiencies, size dependent emission wavelength, high color purity and a low-cost solution processability. These properties make them one of the most promising emitting materials for thin film light-emitting diodes (LEDs) of the future. Although QD-LEDs have been in the focus of science for quite some time, many topics are still neglected, like the dynamics, that show the speed of switching for these LEDs. However, this knowledge could be decisive for the use of such LEDs in communication or sensor technology. This work is intended to provide an overview of the influence of the organic hole transport layer (HTL) on the dynamics of QD LEDs, since the organic semiconductors used represent a limiting factor due to their low mobility. The substances 4,4-Bis(N-carbazolyl)-1,1-biphenyl (CBP), N,N-Bis(3-methylphenyl)-N,N-diphenylbenzidine (TPD) and N,N,N,N-Tetrakis(3-methylphenyl)-3,3-dimethylbenzidine (HMTPD) are used as HTLs. The examined LEDs are constructed in the same way and differ only in the material used for the HTL as well as their thicknesses. The dynamics of these samples will be investigated by electro-optical measurements. To get a better insight, hole only devices were also produced with the HTLs to compare their properties. We assume that these results mark the progress in the development and realization of faster QD LEDs