Charge carrier trapping in highly-ordered lyotropic chromonic liquid crystal films based on ionic perylene diimide derivatives

¹ Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauky 46, 03028 Kyiv, Ukraine
² Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania
³ Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Murmanska 5, 02660 Kyiv, Ukraine
⁴ IMEC, Kapeldreef 75, B-3001 Leuven, Belgium

^a e-mail: kadash@iop.kiev.ua

Received: 1 July 2014
Revised: 21 September 2014
Accepted: 26 September 2014
Published online: 25 November 2014

Abstract

Charge carrier trapping in thin films of lyotropic chromonic liquid crystals (LCLCs) based on ionic perylene diimide derivative and in chemically-similar neutral N,N′-dipentyl-3,4,9,10-perylene-dicarboximide (PTCDI-C5) films is investigated by thermally-stimulated luminescence (TSL) technique. The LCLC films comprise elongated molecular aggregates featuring a long-range orientational order. The obtained results provide direct evidence for the improved energetic ordering (smaller effective energetic disorder) in aggregated LCLC films as compared to conventional PTCDI-C5 films. The width of the density-of-state distribution of 0.09 eV and 0.13 eV was estimated for the LCLC and PTCDI-C5 films, respectively. Relatively small effective energetic disorder in LCLC films is ascribed to formation of macroscopically larger LCLC aggregates.