Tailor-made nanostructures bridging chaos and order for highly efficient white organic light-emitting diodes

Abstract

Organic light-emitting diodes (OLEDs) suffer from notorious light trapping, resulting in only moderate external quantum efficiencies. Here, we report a facile, scalable, lithography-free method to generate controllable nanostructures with directional randomness and dimensional order, significantly boosting the efficiency of white OLEDs. Mechanical deformations form on the surface of poly(dimethylsiloxane) in response to compressive stress release, initialized by reactive ions etching with periodicity and depth distribution ranging from dozens of nanometers to micrometers. We demonstrate the possibility of independently tuning the average depth and the dominant periodicity. Integrating these nanostructures into a two-unit tandem white organic light-emitting diode, a maximum external quantum efficiency of 76.3% and a luminous efficacy of 95.7 lm W −1 are achieved with extracted substrate modes. The enhancement factor of 1.53 ± 0.12 at 10,000 cd m −2 is obtained. An optical model is built by considering the dipole orientation, emitting wavelength, and the dipole position on the sinusoidal nanotexture.

Recent advances in organic light-emitting diodes: toward smart lighting and displays

“…Most recently, an effective way to extract waveguide-mode light has been reported by Reineke and co-workers. 158 In their work, controllable quasiperiodic nano-microstructures with a broad periodicity and depth distribution in the range from tens of nanometers to micrometers are used, which are induced by reactive ion etching (RIE) on poly(dimethylsiloxane) (PDMS) surfaces (Fig. 10c).…”

Hydrophobic stretchable polydimethylsiloxane films with wrinkle patterns prepared via a metal‐assisted chemical etching process using a Si master mold

“…Micro/nanopatterned films are attractive because of their potential applications in various opto‐electronic, biomedical devices based on flexible electronics 1–3 . Various patterns can endow films with enhanced properties such as hydrophobicity or wettability, light scattering or focusing, and stretchability, which are all dependent on the formation of micro/nanoscale patterns 4–10 . Among these properties, hydrophobicity has attracted particular attention because it is highly demanded in various nanopatterning technologies to protect materials from water 11,12 .…”

Centimeter-scale hole diffusion and its application in organic light-emitting diodes for reducing efficiency roll-off and enhancing operation lifetime

“…perpendicular to the applied electric field). So far almost all studies of OLEDs are mainly focused on the carrier dynamics along the direction of electric field; namely the drifting of carriers perpendicular to the planar devices [25][26][27] . However, charge carriers can also diffuse in all directions, including perpendicular to the electric field, as carrier "diffusion" is driven by concentration gradient and is independent of the electric field [28] .…”