High light extraction efficiency into glass substrate in organic light-emitting diodes by patterning the cathode in graded superlattice with dual periodicity and dual basis

Abstract

The newly discovered graded, superlattice photonic crystals with dual periodicity and dual basis present great opportunity for electromagnetic wave control in photonic devices. These graded superlattices can be holographically fabricated by eight beam interference lithography. We have computed, through electrodynamic simulation, the light extraction efficiency of planar, white organic light-emitting diodes where the Al cathode is patterned with the graded superlattice with dual basis. Two graded super-lattices with four-fold and two-fold symmetries are used to pattern the Al cathode. The decrease in power losses to surface plasmon and waveguide modes is explained by the varying plasmon path length and grating cycle, respectively, in the graded pattern. To the authors' best knowledge, the highest light extraction efficiency of 73.1% into the glass substrate in organic light-emitting diodes has been predicted through simulations.

Generation of over 1000 Diffraction Spots from 2D Graded Photonic Super-Crystals

“…The diffraction pattern indicates that GPSC can be formed with very high precision, and the GPSC structure show not only simple periodicity but also those with tens of different in size "atoms" or "molecules" in a unit cell. Simulations predicted a broadband light trapping enhancement in solar cells [16,27] or an enhanced broadband extraction efficiency in OLEDs [15,28] when solar cells or OLEDs are patterned in GPSC, respectively. These experimentally observed fractional diffraction orders help understand the mechanism of broadband enhancement in solar cells or OLEDs patterned in GPSC and promote GPSC applications in these devices.…”

“…GPSC has dual period and even dual symmetry: The square lattices in GPSC have a small period while graded regions have their own symmetry and period [12][13][14]. GPSCs can be used to enhance the broadband light trapping in an Si solar cell, broadband light extraction from organic light emitting diode, and to form a resonance cavity at the boundary of graded and less-graded regions [15][16][17]. By incorporating disorders in the location and radii of the holes in the 2D photonic crystal, topological properties appear in the photonic crystal [18,19].…”

Extraordinary Light-Trapping Enhancement in Silicon Solar Cell Patterned with Graded Photonic Super-Crystals

“…These detectors can collect signals in a large angle of up to 90 • , but it cannot collect the waveguide modes mentioned above. In our simulations of the light extraction in organic light emitting diode devices [32], the fraction of light power in the waveguide modes is also zero. We have assumed zero reflection from waveguide modes in this study.…”

Holographic Fabrication and Optical Property of Graded Photonic Super-Crystals with a Rectangular Unit Super-Cell

“…The second-generation photonic crystals have shown enhanced light-matter interactions [5,6]. Very recently, we have studied a new type of photonic crystals titled graded photonic super-crystals (GPSC) [7][8][9][10][11]. Although the lattices are grouped by the blue and red dots, the size of the basis is different in GPSC.…”

“…"Period 1" is the period for the traditional photonic crystal, while "Period 2" is the second period in the x-direction for the GPSC, as shown in Figure 1. The lattice described by "Period 1" have a square symmetry, while the lattice described by "Period 2" can have square, hexagonal, or five-fold symmetry [7][8][9][10][11]. Thus, the GPSC can have dual-periods and dual-symmetries.…”