Browsing by Author "Wong, T. K. S."

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    Effect of shell thickness on small-molecule solar cells enhanced by dual plasmonic gold-silica nanorods
    (AIP Publishing, 2014-09-19) Xu, X.; Du, Q.; Peng, B.; Xiong, Q.; Hong, L.; Demir, Hilmi Volkan; Wong, T. K. S.; Kyaw, A. K. K.; Sun, X. W.
    Chemically synthesized gold (Au)-silica nanorods with shell thickness of 0 nm-10 nm were incorporated into the bulk heterojunction of a small-molecule organic solar cell. At optimal (1 wt. %) concentration, Au-silica nanorods with 5 nm shell thickness resulted in the highest power conversion efficiency of 8.29% with 27% relative enhancement. Finite-difference time-domain simulation shows that the localized electric field intensity at the silica shell-organic layer interface decreases with the increase of shell thickness for both 520 nm and 680 nm resonance peaks. The enhanced haze factor for transmission/reflection of the organic layer is not strongly dependent on the shell thickness. Bare Au nanorods yielded the lowest efficiency of 5.4%. Light intensity dependence measurement of the short-circuit current density shows that the silica shell reduces bimolecular recombination at the Au surface. As a result, both localized field intensity and light scattering are involved in efficiency enhancement for an optimized shell thickness of 5 nm.
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    Enhanced efficiency of solution-processed small-molecule solar cells upon incorporation of gold nanospheres and nanorods into organic layers
    (Royal Society of Chemistry, 2014) Xu, X.; Kyaw, A. K. K.; Peng, B.; Du, Q.; Hong, L.; Demir, Hilmi Volkan; Wong, T. K. S.; Xiong, Q.; Sun, X. W.
    The significantly enhanced performance upon incorporation of Au nanoparticles in solution-processed small-molecule solar cells is demonstrated. Simultaneously incorporating Au nanospheres into the hole transport layer and Au-silica nanorods into the active layer results in superior broadband absorption improvement in the device with a power conversion efficiency of 8.72% with 31% enhancement.
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    Influence of gold-silica nanoparticles on the performance of small-molecule bulk heterojunction solar cells
    (Elsevier BV * North-Holland, 2015) Xu, X.; Kyaw, A. K. K.; Peng, B.; Xiong, Q.; Demir, Hilmi Volkan; Wang Y.; Wong, T. K. S.; Sun, X. W.
    Light trapping by gold (Au)-silica nanospheres and nanorods embedded in the active layer of small-molecule (SM) organic solar cell has been systematically compared. Nanorod significantly outperforms nanosphere because of more light scattering and higher quality factor for localized surface plasmon resonance (LSPR) triggered by nanorods. The optimum concentration of nanorod was characterized by charge carrier transport and morphology of the active layers. At optimum nanorod concentration, almost no change in the morphology of the active layer reveals that LSPR and scattering effects rather than the morphology are mainly responsible for the enhanced power conversion efficiency. In addition, the preliminary lifetime studies of the SM solar cells with and without Au-silica nanorods were conducted by measuring the current density-voltage characteristics over 20 days. The results show that plasmonic device with nanorods has no adverse impact on the device stability