Electrical transport modelling in organic electroluminescent devices

Abstract

Organic electroluminescent devices (OEDs) emit light when an electric current is applied to a thin film section. They arise from two main technology branches—small molecules and light emitting polymers. Apart from the insight offered into the fundamentals of their physics, which is relevant to topics such as electrical transport in biological systems and molecular computers, understanding how the mobilities in these systems vary with morphology and composition enables the design of improved materials for technological requirements, e.g. fast switching speeds for active matrix displays and polymer field effect transistors. In this review, we have focussed on the models of transport in OEDs that address the unusual nature of this transport and underpin device design. The review concludes with the following point: as new materials for use in OEDs continue to appear, modelling is essential for the prediction of their transport properties, which in turn leads to the establishment of fundamental trends in the behaviour of devices employing them.

Theoretical study of electric field-dependent polaron-type mobility in conjugated polymers

“…Our results for DMeO-PPV are better described as field-independent. The dependence of intra-chain polaron-like mobility on the electric field predicted for PPV and its derivatives is quite different from the Poole-Frenkel form inferred from time-of-flight measurements in organic semiconductors [10].…”

Effects of disorder on the current density and recombination profile in organic light-emitting diodes

“…In principle, it would be possible to investigate these effects by introducing the EGDM in one of the one-dimensional ͑1D͒ OLED device models which are already available. [14][15][16][17][18][19][20][21][22][23][24][25] However, it is presently not clear to what extent the true 3D character of the filamentary transport 26 and recombination processes can be described using a 1D model. More specifically, it is presently not yet clear to what extent bimolecular recombination in materials with Gaussian disorder is properly treated using the Langevin formula.…”

Adaptive Finite Volume Simulation of Electrical Characteristics of Organic Light Emitting Diodes

“…1, is a TPD/Alq 3 two-layer device. Modeling of traps in numerical simulation of OLEDs is widely debated [3]. The electron-hole mobility taking the field-dependent Poole-Frenkel form in the current continuity equations of electron and hole is for shallow trapping of carriers.…”

“…As such, the OLED display appears to be a strong candidate as a replacement technology in a variety of mobile application areas. OLEDs with different thin-film structures, consisting of emitter and carrier transport layers, have recently been reported [2], [3], [4], [5], [6]. According to the simple device geometry in OLEDs, one-dimensional (1D) transport model, the drift-diffusion model, has generally been solved along the transport direction for studying the electrical properties of OLEDs [4], [5], [6].…”