Highly Uniform Colloidal Metasurfaces for the Photoluminescent Enhancement of Quantum Dot Active Layers

Colloidal metasurfaces are two-dimensional arrays of subwavelength resonators generally composed of a precious metal substrate and a deposited layer of colloidal metal nanoparticles, ultimately yielding a functional nanomaterial surface with a total thickness on the order of 100 nanometers. Colloidal metasurfaces, as like other metasurfaces, possess the ability to control and manipulate light in ways thatcannot be done using natural materials, yet have the added benefit of much faster, cheaper, and larger scale construction. The precise construction parameters of these colloidal metasurfaces allow for the tuning of an extreme, in-plane electromagnetic coupling phenomenon that is primarily localized within the metasurface “gap.” Placing active materials (such as nanocrystals, fluorophores, and others) into this gap can lead to a variety of interesting effects that are potentially useful for the construction of larger functional devices. Certain types of active materials have very poor absorption capabilities, making them very difficult and/or inefficient to use as sensing agents and light collectors. Here we show that these colloidal metasurface gaps can be use to enhance the single- and multi-photon absorption efficiencies and subsequent emission intensities of an active layer of semiconducting nanocrystals via the integration of these nanocrystals into the metasurface gap during the metasurface construction process. Colloidal metasurfaces used for active layer enhancement can subsequently be tuned to accommodate many different types of absorbing active layers