Mode Dispersion in Photonic Crystal Organic Light-Emitting Diodes

Abstract

Similar to an electronic lattice determining the motion of electrons in solids, photonic crystals (PhCs) are periodic photonic nanostructures that determine the propagation of photons. By incorporating PhCs into organic light-emitting diodes (OLEDs), the device efficiency and emission spectra can be modified, which can be explained and predicted by the mode dispersion. In this work, we experimentally measure the mode dispersion of 1-D and 2-D PhC OLEDs at different azimuthal angles with angle-resolved electroluminescence spectra. The results are explained using an intuitive geometry approach, which shifts and slices the cone-shaped optical modes to obtain the mode dispersion of PhC OLEDs. We note that the weak cavity mode and a narrow photonic band gap are visible only after eliminating the intrinsic emitter spectrum in the air mode dispersion. In the end, we discuss the implication of mode dispersion on the OLED light extraction.

Cavity Engineering of Perovskite Distributed Feedback Lasers

“…Light with a larger k value is trapped inside the perovskite film forming the WG modes. This process can be illustrated by the dispersion of the optical modes in an energy-momentum space, where the z -axis is the photon energy ( h ν) and the k x – k y plane corresponds to k (Figure a) . From the diagram, the air mode forms a solid cone which defines the dispersion of the outcoupled light, while the transverse electric (TE) and transverse magnetic WG modes form hollow cones.…”

“…In the mode dispersion plot, this is represented by a shift of the WG cones by ±m × k G , leading to partial overlaps between the diffracted WG modes and the air cone (Figure 3b). 31 The part of the WG cones located in the air cone corresponds to the extracted WG modes by the DFB grating, which are manifested by two pairs of crossed stripes in the hν− k y plane (Figure 3c) and two pairs of arcs in the k x −k y plane (Figure 3d).…”

“…This process can be illustrated by the dispersion of the optical modes in an energy-momentum space, where the z-axis is the photon energy (hν) and the k x −k y plane corresponds to k (Figure 3a). 31 From the diagram, the air mode forms a solid cone which defines the dispersion of the outcoupled light, while the transverse electric (TE) and transverse magnetic WG modes form hollow cones. Because the perovskite film is isotropic in the k x −k y plane, the optical modes are all concentric circles with different radii: air < TM WG < TE WG.…”

27‐4: Organic Light‐Emitting Diodes with Directional Polarized Light Emission

“…In the normalized air mode dispersion pattern of the Ircomplex waveguide emission OLED, which eliminated the influence of the emitter spectrum and reveals the line-shape of the TE waveguide mode. [14] The spectral width of the extracted TE waveguide mode is 18 nm, much narrower than the spectral width of Ir(ppy) 3 , therefore the FWHM of the emitted light is significantly reduced. However, it also means a large portion of the emission spectrum does not contribute to the waveguide emission at a given angle.…”

Directional Polarized Light Emission from Thin‐Film Light‐Emitting Diodes

“…In Figure S9, Supporting Information, we plot the normalized air mode dispersion of the Ir‐complex waveguide emission OLED, which eliminated the influence of the emitter spectrum and reveals the line‐shape of the TE waveguide mode. [ 34 ] The spectral width of the extracted TE waveguide mode is 18 nm, much narrower than the spectral width of Ir(ppy) 3 ; therefore, the FWHM of the emitted light is significantly reduced. However, it also means a large portion of the emitter spectrum does not contribute to the waveguide emission at a given angle.…”