The influence of glass transitions on diffusion in OLED stacks
Australian Institute of Nuclear Science and Engineering
Of all of the organic electronic devices thus far conceived, organic light emitting diodes (OLEDs) have been the most successfully applied in a commercial setting. With OLED displays now available in the television and portable device markets, the appetite for their continued development continues to garner considerable research interest. Optimised OLED device architectures typically comprise a number of organic layers with thicknesses between 10 nm and 100 nm sandwiched between inorganic electrodes. Each of the organic layers used in the device is sequentially deposited in an order that optimises charge transport and capture, and light emission from the devices. The fidelity and stability of these multilayer organic stacks is therefore of paramount importance in determining the efficiencies and operational lifetimes of OLED devices. Neutron reflectometry is a powerful technique for probing the layered structures found within OLEDs by utilising selective deuteration to provide contrast between or within the layers.1–3 Modelling the changes in the neutron reflectivity profiles of the OLED stacks deposited onto smooth substrates allows for the visualisation of changes in the layered structure in a non destructive manner. In this talk we will outline our recent efforts to relate the thermal properties of the organic materials used in OLED devices with their diffusion behaviour under thermal stress. Our collaboration with the National Deuteration Facility has led to the synthesis of a number of previously unobtainable deuterated analogues of semiconducting molecules typically used in OLEDs and that have a range of thermal characteristics.3–5 These molecules were used in time-resolved reflectometry experiments that have allowed us to systematically build up an understanding of the importance of glass transitions for the stability of OLED stacks.
Organic matter, Electrodes, Light emitting diodes, Glass, Neutron reflectors, Semiconductor materials
McEwan, J. A., Clulow, A. J., Shaw, P. E., Nelson, A., Yepuri, N. R., Darwish, T., Burn, P. L., & Gentle, I. R. (2016). The influence of glass transitions on diffusion in OLED stacks. Paper presented at 13th AINSE-ANBUG Neutron Scattering Symposium, Sydney, NSW, Australia, 29-30 November 2016.