Colloidal Self-assembled Nanosphere Arrays for Plasmon-enhanced Light Trapping in Thin Film Silicon Solar Cells

2014

To realize high-efficiency thin-film silicon solar cells it is crucial to develop light-trapping methods that can increase absorption of the near- bandgap light in the silicon material. That can be achieved using the far-field scattering properties of metal nanoparticles (MNP) sustaining surface plasmons. The MNPs should be inserted in the back of the cell, embedded in the transparent conductive oxide (TCO) layer which separates the rear mirror from the silicon layers. In this way, a plasmonic back reflector (PBR) is constructed that can redirect light at angles away from the incidence direction and thereby increase its path length in the cell material. In this work, a novel technique is pr…

Plasmonic nanostructures for light trapping in thin-film solar cells

2019

Abstract The optical properties of localized surface plasmon resonances (LSPR) sustained by self-assembled silver nanoparticles are of great interest for enhancing light trapping in thin film photovoltaics. First, we report on a systematic investigation of the structural and the optical properties of silver nanostructures fabricated by a solid-state dewetting process on various substrates. Our study allows to identify fabrication conditions in which circular, uniformly spaced nanoparticles are obtainable. The optimized NPs are then integrated into plasmonic back reflector (PBR) structures. Second, we demonstrate a novel procedure, involving a combination of opto-electronic spectroscopic tec…

Broadband photocurrent enhancement in a-Si:H solar cells with plasmonic back reflectors

2014

The authors acknowledge Francesco Ruffino for the AFM measurements. This work was funded by the EU FP7 Marie Curie Action FP7-PEOPLE-2010-ITN through the PROPHET project (Grant No. 264687), the bilateral CNR/AVCR project "Photoresponse of nanostructures for advanced photovoltaic applications", the MIUR project Energetic (Grant no. PON02_00355_3391233) and by the Portuguese Science Foundation (FCT-MEC) through the Strategic Project PEst-C/CTM/LA0025/2013-14 and the research project PTDC/CTM-ENE/2514/2012. Plasmonic light trapping in thin film silicon solar cells is a promising route to achieve high efficiency with reduced volumes of semiconductor material. In this paper, we study the enhance…

Photocurrent enhancement in thin a-Si:H solar cells via plasmonic light trapping

2014

Photocurrent enhancement in thin a-Si:H solar cells due to the plasmonic light trapping is investigated, and correlated with the morphology and the optical properties of the selfassembled silver nanoparticles incorporated in the cells' back reflector. © 2014 OSA.

Colloidal plasmonic back reflectors for light trapping in solar cells.

2014

A novel type of plasmonic light trapping structure is presented in this paper, composed of metal nanoparticles synthesized in colloidal solution and self-assembled in uniform long-range arrays using a wet-coating method. The high monodispersion in size and spherical shape of the gold colloids used in this work allows a precise match between their measured optical properties and electromagnetic simulations performed with Mie theory, and enables the full exploitation of their collective resonant plasmonic behavior for light-scattering applications. The colloidal arrays are integrated in plasmonic back reflector (PBR) structures aimed for light trapping in thin film solar cells. The PBRs exhib…

Quantifying the trade-off between useful and parasitic absorption of light for plasmonic light trapping in thin silicon films

2016

We apply a combination of photocurrent and photothermal spectroscopic techniques to experimentally quantify the trade-off between useful and parasitic absorption of light in thin hydrogenated microcrystalline silicon (?c-Si:H) films incorporating self-assembled silver nanoparticle arrays, located at the rear side, for improved light trapping via resonant plasmonic scattering. The photothermal technique is used to measure the total absorptance while the photocurrent spectroscopy accounts only for the photons absorbed in the ?c-Si:H layer (useful absorptance); therefore, the method allows for independent quantification of the useful and parasitic absorptance of the plasmonic (or any other) li…

Plasmonic nanostructures for light trapping in photovoltaic

Metallic nanoparticles (NPs), sustaining localized surface plasmon resonances, are currently of great interest for enhancing light trapping in thin film solar cells. To be directly applicable in the photovoltaic industry, the NPs fabrication needs to be simple, reliable, low-cost and scalable. As such, self-assembly processes are most commonly used, and Ag is the preferred material, due to its high radiative efficiency and low imaginary permittivity⁠. After exploring the correlation between structural and optical properties of Ag NPs fabricated by solid- state dewetting process on various substrates, we identified the fabrication conditions in which desirable NPs are obtained, but we also e…

Experimental quantification of useful and parasitic absorption of light in plasmon-enhanced thin silicon films for solar cells application

2016

AbstractA combination of photocurrent and photothermal spectroscopic techniques is applied to experimentally quantify the useful and parasitic absorption of light in thin hydrogenated microcrystalline silicon (μc-Si:H) films incorporating optimized metal nanoparticle arrays, located at the rear surface, for improved light trapping via resonant plasmonic scattering. The photothermal technique accounts for the total absorptance and the photocurrent signal accounts only for the photons absorbed in the μc-Si:H layer (useful absorptance); therefore, the method allows for independent quantification of the useful and parasitic absorptance of the plasmonic (or any other) light trapping structure. W…

Self-assembled silver nanoparticles for plasmon-enhanced solar cell back reflectors: correlation between structural and optical properties

2013

The spectra of localized surface plasmon resonances (LSPRs) in self-assembled silver nanoparticles (NPs), prepared by solid-state dewetting of thin films, are discussed in terms of their structural properties. We summarize the dependences of size and shape of NPs on the fabrication conditions with a proposed structural-phase diagram. It was found that the surface coverage distribution and the mean surface coverage (SC) size were the most appropriate statistical parameters to describe the correlation between the morphology and the optical properties of the nanostructures. The results are interpreted with theoretical predictions based on Mie theory. The broadband scattering efficiency of LSPR…

Direct measurement of optical losses in plasmon-enhanced thin silicon films (Conference Presentation)

2018

Plasmon-enhanced absorption, often considered as a promising solution for efficient light trapping in thin film silicon solar cells, suffers from pronounced optical losses i.e. parasitic absorption, which do not contribute to the obtainable photocurrent. Direct measurements of such losses are therefore essential to optimize the design of plasmonic nanostructures and supporting layers. Importantly, contributions of useful and parasitic absorption cannot be measured separately with commonly used optical spectrophotometry. In this study we apply a novel strategy consisting in a combination of photocurrent and photothermal spectroscopic techniques to experimentally quantify the trade-off betwee…

Broadband light trapping in thin film solar cells with self-organized plasmonic nano-colloids

2015

The intense light scattered from metal nanoparticles sustaining surface plasmons makes them attractive for light trapping in photovoltaic applications. However, a strong resonant response from nanoparticle ensembles can only be obtained if the particles have monodisperse physical properties. Presently, the chemical synthesis of colloidal nanoparticles is the method that produces the highest monodispersion in geometry and material quality, with the added benefits of being low-temperature, low-cost, easily scalable and of allowing control of the surface coverage of the deposited particles. In this paper, novel plasmonic back-reflector structures were developed using spherical gold colloids wi…

Light trapping by plasmonic nanoparticles

2020

Abstract Metallic nanoparticles sustaining localized surface plasmon resonances are of great interest for enhancing light trapping in thin film photovoltaics. In this chapter, we explore the correlation between the structural and optical properties of self-assembled silver nanostructures fabricated by a solid-state dewetting process on various substrates relevant for silicon photovoltaics and later integrated into plasmonic back reflectors. Our study allows us to optimize the performance of nanostructures by identifying the fabrication conditions in which desirable circular and uniformly spaced nanoparticles are obtained. Second, we introduce a novel optoelectronic spectroscopic method that…

Plasmonic and diffractive nanostructures for light trapping—an experimental comparison

2015

Metal nanoparticles and diffractive nanostructures are widely studied for enhancing light trapping efficiency in thin-film solar cells. Both have achieved high performance enhancements, but there are very few direct comparisons between the two. Also, it is difficult to accurately determine the parasitic absorption of metal nanoparticles. Here, we assess the light trapping efficiencies of both approaches in an identical absorber configuration. We use a 240 nm thick amorphous silicon slab as the absorber layer and either a quasi-random supercell diffractive nanostructure or a layer of self-assembled metal nanoparticles for light trapping. Both the plasmonic and diffractive structures strongly…