We report a comparative study on the growth of InAs quantum dots (QDs) on GaAs by metalorganic chemical vapor deposition using triethylgallium (TEGa) and trimethylgallium (TMGa) for the GaAs cap layer. QDs exhibit 1.3μm photoluminescence (PL) at room temperature, as the GaAs cap layer is directly grown on the QDs. The PL emission can be extended to 1.49μm when an In0.25Ga0.75As overgrown layer is inserted between the cap layer and the InAs QDs. The use of TMGa or TEGa for the growth of the GaAs cap layer is essential for a further increase in the emission wavelength of the InAs QDs. Strong PL emission at 1.55μm with a linewidth of 28meV can be obtained as the GaAs cap layer is grown by TEGa, while the optical properties degrade severely when using TMGa.
This paper presents a scheme for the enhancement of silicon solar cells in terms of luminescent emission band and photovoltaic performance. The proposed devices are coated with an luminescent down-shifting (LDS) layer comprising three species of europium (Eu)-doped phosphors mixed within a silicate film (SiO2) using a spin-on film deposition. The three species of phosphor were mixed at ratios of 0.5:1:1.5, 1:1:1, or 1.5:1:0.5 in weight percentage (wt %). The total quantity of Eu-doped phosphors in the silicate solution was fixed at 3 wt %. The emission wavelengths of the Eu-doped phosphors were as follows: 518 nm (specie-A), 551 nm (specie-B), and 609 nm (specie-C). We examined the extended luminescent emission bands via photoluminescence measurements at room temperature. Closely matching the luminescent emission band to the high responsivity band of the silicon semiconductor resulted in good photovoltaic performance. Impressive improvements in efficiency were observed in all three samples: 0.5:1:1.5 (20.43%), 1:1:1 (19.67%), 1.5:1:0.5 (16.81%), compared to the control with a layer of pure SiO2 (13.80%).
Performances of textured crystalline-silicon (c-Si) solar cells enhanced by silver nanoparticles (Ag-NPs) and indium nanoparticles (In-NPs) plasmonic effects are experimentally demonstrated and compared. Plasmonic nanoparticles integrated into textured c-Si solar cells can further increase the absorption and enhance the short-circuit current density (Jsc) of the solar cell. To examine the profile of the proposed metallic particles, the average diameter and coverage of the In-NPs (Ag-NPs) at 17.7 nm (19.07 nm) and 30.5% (35.1%), respectively, were obtained using scanning electron microscopy. Optical reflectance and external quantum efficiency response were used to measure plasmonic light scattering at various wavelengths. Compared to a bare reference cell, the application of In-NPs increased the Jsc of the cells by 8.64% (from 30.32 to 32.94 mA/cm2), whereas the application of Ag-NPs led to an increase of 4.71% (from 30.32 to 31.75 mA/cm2). The conversion efficiency of cells with embedded In-NPs (14.85%) exceeded that of cells with embedded Ag-NPs (14.32%), which can be attributed to the broadband plasmonic light scattering of the In-NPs.
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