On the fabrication of disordered nanostructures for light extraction in corrugated OLEDs

Light scattering OLED substrates relying on disordered self-assemblies are fabricated by microsphere and polymer blend lithography and used for light extraction. We report on a device efficiency enhancement of up to 50 %

Light Management in Thin Film Solar Cells using Internal Scattering Layers made by Polymer Blend Lithography

We report on disordered nano-structured scattering layers fabricated by lateral phase separation of two immiscible polymers, and demonstrate a short-circuit current density enhancement of +13.5%rel in hydrogenated amorphous silicon solar cell

Light trapping in thin film silicon solar cells via phase separated disordered nanopillars

In this work, we have improved the absorption properties of thin film solar cells by introducing light trapping reflectors deposited onto self-assembled nanostructures. The latter consist of a disordered array of nanopillars and are fabricated by polymer blend lithography. Their broadband light scattering properties are exploited to enhance the photocurrent density of thin film devices, here based on hydrogenated amorphous silicon active layers. We demonstrate that these light scattering nanopillars yield a short-circuit current density increase of +33%rel with respect to equivalent solar cells processed on a planar reflector. Moreover, we experimentally show that they outperform randomly textured substrates that are commonly used for achieving efficient light trapping. Complementary optical simulations are conducted on an accurate 3D model to analyze the superior light harvesting properties of the nanopillar array and to derive general design rules. Our approach allows one to easily tune the morphology of the self-assembled nanostructures, is up-scalable and operated at room temperature, and is applicable to other photovoltaic technologies

Polymer blend lithography: a versatile approach for the fabrication of disordered light harvesting nanostructures (Conference Presentation)

Over the last couple of years, photonic materials with tailored -i.e. with deliberately introduced- structural disorder have attracted considerable interest in photovoltaics due to their extended spectral and angular range of effectiveness [1]. Notably, quasi-random nanostructures realized by e-beam lithography (EBL) have been integrated in solar cells as broadband light trapping elements, and have proved to approach the theoretical (Lambertian) limit [2]. Despite recent research efforts aiming at increasing the EBL writing speed [3], alternative routes based on self-assemblies still possess major advantages for an industrial implementation of disordered structures as they allow to rapidly process them over large areas (>>cm2). In this communication, we show that the up-scalable polymer blend lithography technique can be used as a versa-tile platform for fabricating 2D planar, disordered nanostructures that can be exploited in both top-down and bottom-up strategies. Tailored disorder is achieved here by adjusting the process parameters (polymer blend composition and deposition conditions), enabling to tune the morphology and the spatial distribution of the nanostructures produced, and in turn their light harvesting properties. We first use our approach to pattern a resist etching mask, which is employed for transferring disordered nanoholes into a thin hydrogenated amorphous silicon layer by dry etching (top-down route). We report an enhancement of its integrated absorption of +90% under normal incidence, and of up to +200% at large incident angles with respect to an unprocessed absorber [4]. In a second example, we demonstrate that similar structures can serve as a template in a bottom-up configuration, whereby copper indium diselenide nanocrystals are infiltrated into the disordered nano-holes formed in a resist layer. This route, paving the way to wet-processable "photonized" absorbers, is compared to a previous work relying on a serial writing process [5], and the optical properties of the resulting patterned absorbing layers are analysed. We finally elaborate on the significance of these findings for the reverse problem, namely for light extraction in broadband light-emitting diodes

Low- and high-index self-assembled nanopillars as light outcoupling elements in organic light emitting diodes

We report on the development of phase-separated, disordered nanopillars that are integrated as corrugated or as planarized light scattering layers for the outcoupling of waveguide and substrate modes in organic light emitting diodes