Hole injection and transport in ITO/PEDOT/PVK/Al diodes

The paper reports on the hole injection in Poly(N-vinylcarbazole) (PVK) films from an indium tin oxide (ITO) anode treated with poly(3,4)ethylenedioxythiophene/polystyrenesulphonate (PEDT/PSS) usually called PEDOT. The influence of the deposition conditions of PEDOT on the onset voltage of the diodes is first, investigated and an optimised procedure for the surface treatment of ITO with PEDOT is given. Second, the analysis of the I–V characteristics of various devices with different PVK thickness in a temperature range 100–330 K shows that the hole conduction is bulk limited rather than injection limited. A trap assisted space charge conduction model with an exponential distribution of traps well describes our results. A trap density of 4×1018 cm−3 and a characteristic energy Et−EHOMO=0.15 eV were deduced. A comparison with a conduction model based on trap free material but with electric field dependant mobility is provided.