Flexible external light extraction in organic light-emitting diodes by porous PDMS film fabricated by high-pressure steam process

Abstract

In this study, a flexible porous film was proposed as a light-scattering layer for enhancing the external light extraction in organic light-emitting diodes (OLEDs) by a high-pressure steam process. The pore penetration depth and surface morphology of the flexible porous film were affected by the viscosity of the polydimethylsiloxane (PDMS) solution. Moreover, the porous structures influenced the total transmittance, external quantum efficiency (EQE), and view angle. Consequently, although the total transmittance decreased due to the porous structure, the EQE improved by 30% compared to that of OLEDs without the porous film. This improvement can be attributed to the scattering effect, resulting from the difference in refractive indices between the embedded air cavities and porous layer, which depends on the penetration depth and surface morphology. Furthermore, a flexible porous film based on PDMS presents an effective and a simple approach for achieving high efficiency in flexible OLEDs.