Poly(methyl methacrylate) Films with High Concentrations of Silicon Quantum Dots for Visibly Transparent Luminescent Solar Concentrators

Abstract

Silicon quantum dots (Si QDs) are attractive, nontoxic luminophores for luminescent solar concentrators (LSCs). Here, we produced Si QD/poly(methyl methacrylate) (PMMA) films on glass by doctor-blading polymer solutions and achieved films with low light scattering at an order of magnitude higher Si QD weight fraction than has been achieved previously in the bulk. We suggest that the fast solidification rate of films as compared to slow bulk polymerization is an enabling factor in avoiding large agglomerates within the nanocomposites. Scanning electron microscopy confirmed that ∼100 nm or larger QD agglomerates exist in light-scattering films, and photoluminescence intensity measurements show that light scattering, if present, significantly reduces waveguiding efficiencies for LSCs. Nonscattering films fabricated in this work exhibit high ultraviolet absorption (>80%) paired with high visible transmission (>87%) and minimal visible haze (∼1%), making them well suited for semitransparent coatings for LSCs realized as solar harvesting windows.

Luminescent Solar Collectors: Quo Vadis?

“…Quick solidification of PMMA leads to low light-scattering films with an order of magnitude higher QD weight fraction than previously reported nonscattering bulk-polymerized Si QD/PMMA nanocomposites. [164] 3D macroporous photonic crystals have been proposed for the fabrication of efficient photon reflectors for QD-coated LSCs. Characterization of a 2.8 × 1.5 × 0.1 cm device with an integrating sphere showed that adapting the reflection band to the emission profile of the QD emitter improves the light-trapping efficiency from 73.3% to 95.1%.…”

“…[167] The toxicity of classical QDs containing metals such as Cd or Pb has triggered the search for alternative nanomaterials as emitters. Besides the already discussed silicon QDs, [158,160,163,164] several groups have investigated CDs as possible nontoxic emitters. [161,[168][169][170][171][172][173][174][175][176] Zhou et al prepared CDs modified by a treatment with oleylamine in order to reduce absorption in long wavelengths, and thus, SA.…”

Review on Colloidal Quantum Dots Luminescent Solar Concentrators

“…Hill et al. investigated the performance of an LSC based on bare silicon QDs [166] . Si QDs of varying concentrations were embedded in PMMA and doctor bladed with various thicknesses onto glass to form LSC prototypes.…”

“…Although large scattering effects were noticeable even with a QD loading of 0.15 wt%, increasing the solidification rate decreased QD agglomerations and improved waveguide efficiency. A 1 % solidified LSC exhibited a high UV absorption>80 % and visible transmission>87 % with haze<1 % [166] . High light scattering of incident light off the nanoparticle's surface is an important factor for high absorption efficiency.…”

The Hidden Potential of Luminescent Solar Concentrators

“…[ 3,11,14,15 ] Device efficiencies tend to be modest, with values of 7.1% [ 16 ] for a device employing GaAs photovoltaics (PVs) and 4.2% using silicon PV [ 17 ] being among the highest reported. Some other notable examples of conventional LSC design deployments include noise barriers, [ 13,18 ] artworks, [ 19,20 ] greenhouses, [ 21 ] roofing elements, [ 22 ] urban furniture, [ 23 ] and bicycle sheds, [ 23,24 ] and, in the more transparent state, building windows, [ 25,26 ] among others.…”