Thermally induced surface instabilities in polymer light emitting diodes

Abstract

The role of thermal gradients and their attendant mechanical stresses in the overall stability of organic electronic devices has been elucidated through the occurrence of spiral shaped blisters that develop on the surface of suitably biased polymer light emitting diodes. A model based on the spontaneous disordering (or ordering) of polymeric thin film systems has been used to explain the formation and growth of these blisters. The model is shown to provide insights into how thermal stresses affect the overall stability of organic electronic devices. The implications of the results are then discussed for the design of flexible organic electronic devices.

A perturbation analysis on solid polymer surfaces

“…The J s s and J g s are associated with the first and the second terms, and the J s v and J l v to the third and the fourth terms in Eq. (11). See the text for details.…”

“…The instabilities of surfaces have been a topic of interest both theoretically and experimentally [7][8][9][10][11]. First, to describe the change in the amplitude of the surface fluctuation, we introduce a linear stability model.…”

Adhesion and degradation of organic and hybrid organic-inorganic light-emitting devices

“…19,20 Interfacial delamination around dust particles or resulting nanovoids has also been suggested as a mechanism for OLED failure. 21,22 This has been shown to occur by blister formation, bubbles, and spiral buckles present also in encapsulated devices. 21,[23][24][25][26] However, the crack driving forces for these interfacial failure mechanisms have not been explored for the range of device geometries that are relevant to OLED structures.…”

“…21,22 This has been shown to occur by blister formation, bubbles, and spiral buckles present also in encapsulated devices. 21,[23][24][25][26] However, the crack driving forces for these interfacial failure mechanisms have not been explored for the range of device geometries that are relevant to OLED structures. There is also a need to compare the crack driving forces with measurements of adhesion energies for possible bi-material pairs in OLED/HOILED structures.…”

Mapping Temperature in OLED Displays Using CCD Thermoreflectance

“…High temperatures accelerate degradation in OLEDs [1], [2], can cause thermal runaway [3], and can also lead to surface instabilities in the organic layers [4]. The problem of thermal management is exacerbated in devices with flexible or transparent substrates, which have poor thermal conductivity, as well as in high-power devices or large-area displays [5], [6].…”