One of the most promising approaches to produce industrial-compatible Transparent Conducting Materials (TCMs) with excellent characteristics is the fabrication of TCO/metal/TCO multilayers. In this article, we report on the electro-optical properties of a novel high-performing TCO/metal/TCO structure in which the intra-layer is a micro-structured metallic grid instead of a continuous thin film. The grid is obtained by evaporation of Ag through a mask of polystyrene colloidal micro-spheres deposited by the Langmuir-Blodgett method and partially dry-etched in plasma. IZO/Ag grid/IZO structures with different thicknesses and mesh dimensions have been fabricated, exhibiting excellent electrical characteristics (sheet resistance below 10 Ω/□) and particularly high optical transmittance in the near-infrared spectral region as compared to planar (unstructured) TCM multilayers. Numerical simulations were also used to highlight the role of the Ag mesh parameters on the electrical properties.

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Photonic microstructures placed at the topside of photovoltaic cells are currently one of the preferred light management solutions to obtain efficiency enhancement due to the increment of the optical absorption produced in the active medium of the devices. Herein{,} we present the results concerning a practical{,} low-cost and scalable approach to integrate metal-oxide based light trapping microstructures on the front contact of amorphous silicon thin film solar cells. A colloidal lithography method was used to pattern the wavelength-sized pyramidal-like features composing the structures{,} made of two different transparent materials{,} TiO2 and IZO{,} allowing the detailed study of the influence of their geometrical parameters on the optoelectronic properties of the devices. These top coating structures are deposited as a post-process after the solar cell fabrication{,} thus facilitating and broadening their industrial applicability. Measurements of the light absorption{,} external quantum efficiency and I–V curves revealed that the structured coatings provide strong broadband improvements in the generated current{,} due to the suppression of reflected light at short wavelengths and the increment of the optical path length of the longer wavelengths (via light scattering){,} within the amorphous silicon layer. As a result{,} in the four types of structures analyzed in this study{,} remarkable increments were achieved in the cells’ efficiencies (up to 14.4%) and generated currents (up to 21.5%){,} with respect to the flat reference cells.

A novel generation of flexible opto-electronic smart applications is now emerging{,} incorporating photovoltaic and sensing devices driven by the desire to extend and integrate such technologies into a broad range of low cost and disposable consumer products of our everyday life and as a tool to bring together the digital and physical worlds. Several flexible polymeric materials are now under investigation to be used as mechanical supports for such applications. Among them{,} cellulose{,} the most abundant organic polymer on the Earth{,} commonly used in the form of paper{,} has attracted much research interest due to the advantages of being recyclable{,} flexible{,} lightweight{,} biocompatible and extremely low-cost{,} when compared to other materials. Cellulose substrates can be found in many forms{,} from the traditional micro-cellulose paper used for writing{,} printing and food/beverage packaging (e.g. liquid packaging cardboard){,} to the nano-cellulose paper which has distinct structural{,} optical{,} thermal and mechanical properties that can be tailored to its end use. The present article reviews the state-of-the-art related to the integration and optimization of photonic structures and light harvesting technologies on paper-based platforms{,} for applications such as Surface Enhanced Raman Scattering (SERS){,} supporting remarkable 107 signal enhancement{,} and photovoltaic solar cells reaching [similar]5% efficiency{,} for power supply in standalone applications. Such paper-supported technologies are now possible due to innovative coatings that functionalize the paper surfaces{,} together with advanced light management solutions (e.g. wave-optical light trapping structures and NIR-to-visible up-converters). These breakthroughs open the way for an innovative class of disposable opto-electronic products that can find widespread use and bring important added value to existing commercial products. By making these devices ubiquitous{,} flexible and conformable to any object or surface{,} will also allow them to become part of the core of the Internet of Things (IoT) revolution{,} which demands systems{'} mobility and self-powering functionalities to satisfy the requirements of comfort and healthcare of the users.

Optical solutions are promising for Perovskite solar cell (PSC) technology, not only to increase efficiency, but also to allow thinner absorber layers (higher flexibility) and improve stability. This work optimized the combined anti-reflection and scattering properties of two types of light trapping (LT) structures, based on TiO2 semi-spheroidal geometries with honeycomb periodicity, for application in PSCs with substrate configuration and different perovskite layer thicknesses. Their optically lossless material (TiO2) allows the structures to be patterned in the final processing steps, integrated in the cells’ top n contact, therefore not increasing the surface area of the PV layers and not degrading the electric performance via recombination. Therefore, this strategy circumvents the typical compromise of state-of-the-art LT approaches between optical improvements and electrical deterioration, which is particularly relevant for PSCs since their main recombination is caused by surface defects. When patterned on the cells’ front, the wave-optical micro-features composing the LT structures yield up to 21% and 27% photocurrent enhancement in PSCs with conventional (500 nm thick) and ultra-thin (250 nm) perovskite layers, respectively; which are improvements close to those predicted by theoretical Lambertian limits. In addition, such features are shown to provide an important encapsulation role, preventing the cells’ degradation from UV penetration.