We demonstrate enhanced absorption in solar cells and enhanced light emission in OLEDs by light interaction with a periodically structured microlens array. We simulate n-i-p perovskite solar cells with a microlens at the air-glass interface, with rigorous scattering matrix simulations. The microlens focuses light in nanoscale regions within the absorber layer enhancing the solar cell. Optimal period of ~700 nm and microlens height of ~800-1000 nm, provides absorption (photocurrent) enhancement of 6% (6.3%). An external polymer microlens array on the air-glass side of the OLED generates experimental and theoretical enhancements >100%, by outcoupling trapped modes in the glass substrate.

A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor η out , which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase η out by fabricating OLEDs on novel flexible nanopatterned substrates that result in a >2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning η out ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed for blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost-effectively by direct room-temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome-shaped convex nanopatterns with height of ∼280-400 nm and pitch ∼750-800 nm were found to be optimal. Substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs. OLED Light Outcoupling

Organic solar cells have demonstrated rapidly increasing efficiencies, but typically absorb less than half of the incident solar spectrum. To increase broadband light absorption, we rigorously design experimentally realizable solar cell architectures based on dual photonic crystals using scattering matrix simulations. There is a polymer microlens on the glass coupled with a photonic-plasmonic crystal at the metal cathode on the back of the cell. The microlens focuses light on the periodic nanostructure that in turn strongly diffracts light. Waveguiding modes and surface plasmon modes enhance long wavelength absorption. The optimal architecture has a period of 500 nm for both arrays, resulting in absorption enhancement of 49% and photocurrent enhancement of 58% relative to the flat cell, for nearly lossless metal cathodes. The enhanced absorption approaches the Lambertian limit. Misalignment between the two photonic crystals leads to about 1% loss of performance. Simulations incorporating experimental dielectric functions for metal cathode and ITO, using a real space methodology find the enhancement of 38% for the photocurrent and 36% for the weighted absorption due to parasitic losses mainly in the metal cathode. This solar architecture is particularly amenable for fabrication since it does not require spin coating of organic layers on corrugated surfaces, but instead requires nanoimprinting an organic layer, followed by metal cathode deposition. This dual photonic crystal architecture has great potential to achieve >12% efficient single junction organic solar cells and to control photons by focusing light on nanostructures and plasmonic components.