A facile route to efficient, low-cost flexible organic light-emitting diodes: utilizing the high refractive index and built-in scattering properties of industrial-grade PEN substrates.

An industrial-grade polyethylene naphthalate (PEN) substrate is explored as a simple, cost-effective platform for high-efficiency organic light-emitting diodes (OLEDs). Its high refractive index, combined with the built-in scattering properties inherent to the industrial-grade version, allows for a significant enhancement in outcoupling without any extra structuring or special optical elements. Flexible, color-stable OLEDs with efficiency close to 100 lm W(-1) are demonstrated.