Different interface orientations of pentacene and PTCDA induce different degrees of disorder
- PDF / 407,250 Bytes
- 5 Pages / 595 x 794 pts Page_size
- 53 Downloads / 150 Views
NANO EXPRESS
Open Access
Different interface orientations of pentacene and PTCDA induce different degrees of disorder Angela Poschlad1,2 , Velimir Meded1,2 , Robert Maul1 and Wolfgang Wenzel2*
Abstract Organic polymers or crystals are commonly used in manufacturing of today‘s electronically functional devices (OLEDs, organic solar cells, etc). Understanding their morphology in general and at the interface in particular is of paramount importance. Proper knowledge of molecular orientation at interfaces is essential for predicting optoelectronic properties such as exciton diffusion length, charge carrier mobility, and molecular quadrupole moments. Two promising candidates are pentacene and 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA). Different orientations of pentacene on PTCDA have been investigated using an atomistic molecular dynamics approach. Here, we show that the degree of disorder at the interface depends largely on the crystal orientation and that more ordered interfaces generally suffer from large vacancy formation. Keywords: Organic interfaces, Organic electronic devices, Interface disorder, Molecular dynamics, PTCDA, Pentacene
Background Organic light emitting diodes (OLEDs), organic solar cells, organic thin films transistors, etc. are made of organic polymers or crystals [1-3]. The effect of the disorder in organic devices on optoelectronic properties was analyzed by Rim et al. [4]. They showed an increased photocurrent generation with improved molecular order. It occurs due to the influence of the stacking on the exciton diffusion length. Hu et al. measured a strong dependence of the conductance across highly oriented pentacene nanocrystals on the packing orientation [5]. The influence of packing on charge transport in organic solids was also analyzed using Monte Carlo methods [6]. Kwiatkowski et al. [6] were able to predict the mobilities of electron and holes for ordered and disordered Alq3. Different functional organic materials were reviewed by Ishii et al. [7]. They highlighted the energy level alignment and electronic structures at organic/inorganic and organic/organic interfaces of, for example, Alq3,
*Correspondence: WW:[email protected] 2 Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe, 76131, Germany Full list of author information is available at the end of the article
3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) and 1,4,5,8-tetrathiafulvalene (TTF). In our work, the morphology of interfaces between pentacene [8] and PTCDA [9] was analyzed (Figure 1a). Both molecules form different crystal modifications. Pentacene is known to have a high temperature (HT) and a low temperature (LT) polymorph. Yoneya et al.[8] showed that the LT polymorph is destabilized by substrates and transforms into HT polymorph. Therefore, the HT polymorph was used as the base for simulations. For PTCDA, the α polymorph [9] was used. Molecular orientation at interfaces is decisive for predicting optoelectronic properties such as exciton diffusion length [10], charge carrier
Data Loading...
