Enhanced light extraction efficiency of OLEDs with quasiperiodic diffraction grating layer

Abstract

We presented enhanced light extraction efficiency of organic light emitting diodes (OLEDs) cells with a nano-sized diffraction grating layer. Various diffraction gratings of different morphologies including linear, cubic, hexagonal and quasiperiodic patterns were fabricated by multiplexing light interference exposure on an azobenzene thin film. The effect of diffraction grating layer on device performances including luminous properties and quantum efficiency was investigated. In contrast to periodic grating patterns, the quasiperiodic structures leading broadband light extraction resulted in improved external quantum efficiency and power efficiency by 73% and 63%, respectively, compared to conventional OLED with flat surface of glass substrate.

Low-cost light manipulation coatings for polymer solar cell photocurrent increase under various incident angles

“…Previous studies suggest that quasi-random textures may produce stronger scattering than highly ordered ones [18]. As the computational method is based on pre-defined ideal structures, it cannot account for the quasirandomness which is relatively large for both nanoPDMS and microPDMS having dome diameter disperties of 0.43 and 0.53, respectively.…”

“…Furthermore, miscibility of the two polymers in the blends controls the quasi-randomness of pore diameter dispersity and higher dispersities are obtained for the less miscible P3HT:PMMA blends. Despite the fact that quasi-random textured surfaces are suspected to produce more efficient light manipulation than ideal structures [18], and that previous studies suggest that phase separated polymer thin films have a great potential for the fabrication of anti-reflective layers [14,15], so far there is no evidence that they can be successfully employed to enhance the performances of PSCs.…”

Photonics design theory enhancing light extraction efficiency in quantum dot light emitting diodes

“…where k 0 and θ are the wavenumber and exit angle of the light in free space, k wg is the waveguide vector and k G = 2π/d is the grating vector of period d [52]. This decrease in the wavenumber allows the light to escape into air.…”

Enhanced light out-coupling efficiency and reduced efficiency roll-off in phosphorescent OLEDs with a spontaneously distributed embossed structure formed by a spin-coating method

“…Therefore, many methods have been done around increasing the out-coupling efficiency of OLEDs, including: using microlens array, [18][19][20] large half sphere lens, 21 surface roughness at the glass/air interface, 22 periodic photonic crystal, [23][24][25] microcavity OLEDs, [26][27][28] high index substrates, 29 metal free OLED, 30 and spontaneously formed buckles. [31][32][33][34] Among all these techniques, introducing spontaneously formed buckles in OLEDs have been proved to be an effective approach because of the enhanced light extraction without introducing spectral changes and directionality. This means the color gamut does not alter along the viewing direction, which is important for information displays.…”

“…However, the spontaneously formed buckles were usually fabricated by the techniques such as multiplexing light interference 32 or nano-imprinting, 33,34 which require more complicated and expensive fabrication processes and thus are not costeffective for commercial applications. Thus, further studies are still required to increase out-coupling efficiency without spectral changes through a simple and cost-effective process.…”