Polymer Brush Guided Formation of Conformal, Plasmonic Nanoparticle‐Based Electrodes for Microwire Solar Cells

Abstract

3958 wileyonlinelibrary.com conformal manner. [ 8 ] Conductive oxides such as ZnO or ITO are one attractive possibility. However, while ITO can be deposited in a relatively conformal manner on nanowires, the scarcity of indium in the earth crust has led researchers to seek alternative solutions. Such alternatives include graphene, [ 9 ] carbon nanotubes, [ 10,11 ] conductive polymers, [ 12,13 ] nanocellulose fi ber papers [ 14 ] or metal nanowire mesh. [15][16][17][18] While metal nanoarchitectures are potentially interesting electrode materials, their application on complex surfaces, such as, e.g., 3D structured solar cells, is a challenge. This contribution presents a scalable process that allows to fabricate silicon microwire-based solar cells modifi ed with a highly conformal silver or gold nanoparticle fi lm. It will be shown that these metal nanoparticle coatings perform a dual function and not only act as a conductive electrode layer but also enhance light capture due to the fact that the metal nanoparticles behave as plasmonic scattering elements. [19][20][21] The proposed process is outlined in Figure 1 and uses an ultrathin coating consisting of densely grafted polymer chains, which are tethered with one chain end to the surface, to guide the formation of a metal nanoparticle-based electrode layer. These surface-grafted polymer fi lms are often colloquially referred to as "polymer brushes." Polymer brush coatings can be fabricated in a bottom-up fashion via surface-initiated polymerization [ 22 ] and have already been successfully used as templates for the fabrication of thin inorganic [23][24][25][26] and metallic fi lms. [ 27 ] Surfaceinitiated polymerizations are attractive in that they allow to control the thickness of the metal nanoparticle fi lm by controlling the polymer brush thickness and are also compatible with photopatterning strategies, which potentially could allow access to microstructured metal nanoparticle coatings. Furthermore, being a bottom-up strategy, surface-initiated polymerizations also allow facile and controlled deposition of thin, conformal polymer coatings on complex, 3D structured substrates, such as, e.g., nano-or microwires or nano-or microporous materials, which is challenging to achieve using more conventional polymer fi lm forming methods such as spin-or drop-casting. The fabrication of the metal nanoparticle-based electrodes starts with modifi cation of the solar cell surface with an appropriate polymerization initiator, followed by surface-initiated polymerization to generate a thin polymer brush fi lm (Figure 1 ). In the present work, atom transfer radical polymerization (ATRP) was used to grow the polymer brushes. After that, the polymer This report explores the use of sacrifi cial thin polymer fi lms prepared by surface-initiated polymerization as a template for the fabrication of highly conformal metal nanoparticle solar cell electrodes. As a fi rst proof-of-principle, the use of this method is demonstrated to prepare top electrodes on planar and microwire-based ...

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

“…Most often, the templates that are used to produce metal nanoparticles are carboxylic acid side chain functionalized brushes (such as PHEMA postfunctionalized with succinic anhydride) ,, or basic brushes such as PDMAEMA, ,,,, its quaternized analogue PMETAC ,, or P4VP. ,, The metallic precursors are typically introduced into the brushes by impregnating them with an aqueous solution of metallic salt. Nanoparticles will be formed after chemical reduction of the metallic salt.…”

Degrafting of Poly(poly(ethylene glycol) methacrylate) Brushes from Planar and Spherical Silicon Substrates

“…Preparation of ATRP Initiator-Modified Surface S5. 49 Silicon oxide wafers were first sonicated in ethanol, water, acetone, and ethanol (5 min each). The wafers were then dried under a flow of nitrogen and exposed to oxygen plasma for 15 min.…”

Tungsten-Coated Silicon Nanopillars as Ultra-Broadband and Thermally Robust Solar Harvesting Materials

“…With the rapid exhaustion of fossil fuels and depletion of the ozone layer, solar radiation has been supposed as a promising replacement energy source to meet the ever-increasing power demand due to its cleanness and abundance. Thus, broadband solar harvesting devices have attracted increasing attention in real-life optical applications, including photodetection, − photocatalysis, − solar energy harvesting and conversion, − and solar thermophotovoltaic (STPV). − Correspondingly, a variety of light-absorbing structures have been extensively studied for decades to harvest solar energy much more efficiently. , Recently, metamaterial perfect absorbers based on plasmonic noble metals, such as gold and silver, have exhibited excellent and versatile capabilities in controlling the electromagnetic response. Extreme optical absorption performance can be achieved by adjusting the nanostructure design on the top surface due to the localized surface plasmon resonance effects. − However, this outstanding optical absorption only occurs within a narrow bandwidth for a certain nanopattern design.…”