We demonstrate the highly effective extraction of waveguided light from the active region of organic light-emitting devices using a non-diffractive dielectric grid layer placed between the transparent anode and the substrate. The subanode grid couples out all waveguide mode power into the substrate without changing the device electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficacy for green phosphorescent organic light-emitting devices from 15 ± 1% and 36 ± 2 lm W -1 to 18 ± 1% and 43 ± 2 lm W -1 . These characteristics are further increased to 40 ± 2% and 95 ± 4 lm W -1 when all glass modes are also extracted. The use of a thick electron transport layer further reduces surface plasmon modes, resulting in an increase in the substrate and air modes by 50 ± 8% compared with devices lacking the grids. The sub-anode grid has minimal impact on organic light-emitting device emission wavelength and viewing angle, and is likely to prove beneficial for a broad range of display and lighting applications. E lectrophosphorescent organic light-emitting devices (PHOLEDs) can yield 100% internal quantum efficiency (η IQE ) 1,2 . This provides an external quantum efficiency (η EQE ) of ∼20% without outcoupling enhancement. The remaining emitted photons are trapped in the substrate due to total internal reflection at the glass-air interface 3 , are guided within the organic material layers and the transparent anode because of their high refractive indices compared to glass 4 , and are dissipated at the organic-cathode interface by exciting surface plasmon modes 5,6 .Numerous methods have been explored to solve the problem of inefficient optical extraction. To overcome total internal reflection at the glass substrate-air interface, microlens arrays 7,8 and microsphere scattering layers 9 have been used. These solutions are effective for coupling out the majority of substrate mode photons, but have no effect on optical power confined within the high-index organic and anode regions (waveguide modes) or at the metalorganic interface (surface plasmon modes). To extract the waveguided light, internal outcoupling structures can be categorized into two groups. One is to modulate the photon states to extract light via optical gratings or photonic crystals 10,11 . This method leads to emission properties that depend on both viewing angle and wavelength, making it incompatible with display and lighting applications. A second is to scatter the waveguided optical power using refractive index contrast or corrugated structures within the waveguide region itself. For example, high-index substrates 12,13 and outcoupling structures embedded in the organic layers have proven effective. High-index glass, however, is expensive, and raises concerns about toxicity and environmental impact 14 . Other implementations such as low-index grids 15,16 or surface corrugations 17 introduce unwanted modifications into the device active region which is already affecting the optimized optoelectronic performance...
Using a combination of Fourier transform infrared (FTIR) spectroscopy and physics-based degradation models, we find that the early aging of small molecular weight organic photovoltaic (OPV) cells is due to photochemical degradation of the C60acceptor layer.
Hybrid organic-inorganic polaritons are formed by the simultaneous strong coupling of two degenerate excitons and a microcavity photon at room temperature. Wannier-Mott and Frenkel excitons in spatially separated ZnO and 3,4,7,8-napthalene tetracarboxylic dianhydride (NTCDA) layers, respectively, placed in a single Fabry-Perot microcavity contribute to the interaction with the cavity. A Rabi splitting of (322±8) meV between the upper and middle branches of the three branch polariton energy-momentum dispersion is observed. This is compared to only (224±22) meV and (218±8) meV Rabi splittings for NTCDA-only and ZnO-only reference cavities, respectively, and indicates that the excitonic component of the polariton is a Frenkel-Wannier-Mott hybrid. Unlike previous reports of hybrid polaritons, the mixing of the organic and inorganic eigenstates occurs independently of angle due to their energetic degeneracy, and can be tailored by adjusting the optical field distribution within the cavity.
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