Abstract
In this study, we report the use of Al2O3 nanoparticles in combination with fluorine doped tin oxide (F:SnO2, aka FTO) thin films to form hazy Al2O3-FTO nanocomposites. In comparison to previously reported FTO-based nanocomposites integrating ZnO and sulfur doped TiO2 (S:TiO2) nanoparticles (i.e., ZnO-FTO and S:TiO2-FTO nanocomposites), the newly developed Al2O3-FTO nanocomposites show medium haze factor HT of about 30%, while they exhibit the least loss in total transmittance Ttot. In addition, Al2O3-FTO nanocomposites present a low fraction of large-sized nanoparticle agglomerates with equivalent radius req > 1 μm; effectively 90% of the nanoparticle agglomerates show req < 750 nm. The smaller feature size in Al2O3-FTO nanocomposites, as compared to ZnO-FTO and S:TiO2-FTO nanocomposites, makes them more suitable for applications that are sensitive to roughness and large-sized features. With the help of a simple optical model developed in this work, we have simulated the optical scattering by a single nanoparticle agglomerate characterized by bottom radius r0, top radius r1, and height h. It is found that r0 is the main factor affecting the HT(λ), which indicates that the haze factor of Al2O3-FTO and related FTO nanocomposites is mainly determined by the total surface coverage of all the nanoparticle agglomerates present.
Highlights
Transparent Conductive Oxides (TCOs) constitute a unique class of thin film materials that simultaneously exhibit high optical transparency as well as good electrical conductivity
We have successfully identified the influence of the shape parameters of the agglomerates on the optical scattering and established a direct correlation between morphological and optical properties common to Al2O3-FTO and related FTO nanocomposites
Among the three series of nanocomposites, Al2O3-FTO nanocomposites appear most favorable to be integrated in solar devices that are highly sensitive to TCO roughness and large feature sizes
Summary
Transparent Conductive Oxides (TCOs) constitute a unique class of thin film materials that simultaneously exhibit high optical transparency as well as good electrical conductivity. The obtained ZnO-FTO and S:TiO2-FTO nanocomposites exhibit superior haze factor (HT) of more than 60% Using these nanocomposites as electrodes in thin film solar cells, the transmitted light could undergo scattering and travel longer paths in the subsequent absorber layer. The optical absorption in the active layer is expected to be higher, the conversion efficiency could be potentially improved [12,13,14] Both nanocomposites showed decreased total transmittance (Ttot); and S:TiO2-FTO nanocomposites were reported to exhibit large-sized nanoparticle agglomerates. These factors may eventually jeopardize the performance of final photovoltaics devices. For the first time, a comprehensive study of the structure-property relations for such type of FTO-based nanocomposites, which provides significant guidelines for designing and controlling the properties of hazy TCO nanocomposites for versatile applications
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