Joule heat-induced breakdown of organic thin-film devices under pulse operation

摘要

We investigated the influence of the substrate's thermal conductivities (κ) and the widths of the electrical pulses (τ_(pulse)) on the maximum current densities (J_(max)) in organic thin-film devices. We also estimated the temperature rise (△T) inside devices under the pulse operation using numerical calculations to interpret the observed differences in J_(max) For a long τ_(pulse)of 5 μs, J_(max) is higher for devices with high-/: sapphire substrates (around 1.2 kA/cm~2) than devices with low-κ plastic substrates (around 0.4 kA/cm~2). This is because high-κ sapphire substrates can work as heat sinks to relax AT for such a long τ_(pulse). Operation of devices with high-κ sapphire substrates for a short τ_(pulse) of 70 ns resulted in further relaxation of △T, leading to an increase of J_(max) to around 5 kA/ cm~2. Interestingly, for such a short τ_(pulse) devices with high-κ sapphire and low-κ plastic substrates showed similar J_(max) and AT values, the reason for which may be that it is difficult for the generated Joule heat to travel to the substrate across a low-k organic layer within this short time.