Can plasmonic Al nanoparticles improve absorption in triple junction solar cells?

Abstract

Plasmonic nanoparticles located on the illuminated surface of a solar cell can perform the function of an antireflection layer, as well as a scattering layer, facilitating light-trapping. Al nanoparticles have recently been proposed to aid photocurrent enhancements in GaAs photodiodes in the wavelength region of 400–900 nm by mitigating any parasitic absorption losses. Because this spectral region corresponds to the top and middle sub-cell of a typical GaInP/GaInAs/Ge triple junction solar cell, in this work, we investigated the potential of similar periodic Al nanoparticles placed on top of a thin SiO2 spacer layer that can also serve as an antireflection coating at larger thicknesses. The particle period, diameter and the thickness of the oxide layers were optimised for the sub-cells using simulations to achieve the lowest reflection and maximum external quantum efficiencies. Our results highlight the importance of proper reference comparison, and unlike previously published results, raise doubts regarding the effectiveness of Al plasmonic nanoparticles as a suitable front-side scattering medium for broadband efficiency enhancements when compared to standard single-layer antireflection coatings. However, by embedding the nanoparticles within the dielectric layer, they have the potential to perform better than an antireflection layer and provide enhanced response from both the sub-cells.

Nanoparticle Scattering for Multijunction Solar Cells: The Tradeoff Between Absorption Enhancement and Transmission Loss

“…Although front side NP arrays have been shown to improve in III-V solar cells in the past [8,9], these examples were benchmarked against devices with non-optimal antireflection, as opposed to the optimised double layer ARC used as comparison here. It has already been shown that Al NPs are unlikely to lead to an improved anti-reflection compared to an optimised ARC [17]. We add to this by demonstrating clearly the limitations of enhancing the photocurrent of highefficiency solar cells using Al or AlInP NP arrays on the front face, even in the case where the absorbing layer is extremely thin and requires absorption enhancement via oblique photon scattering.…”

“…All other layer thicknesses are as in the experimental Sample Set 1. To simplify the study, only the performance of the In 0.01 GaAs middle cell is monitored, since the difficulty of achieving good anti-reflection in both upper subcells simultaneously has already been investigated by Yang [17]. We choose not to use a drift-diffusion model here, but instead make the simplifying assumption that all photogenerated carriers in the middle cell are extracted as current.…”

“…A more recent computational study has shown that Al NP arrays embedded in a single-layer ARC exhibit transmission losses compared to a Nanoparticle scattering for multi-junction solar cells: the trade-off between absorption enhancement and transmission loss Alexander Mellor, Nicholas P. Hylton, Hubert Hauser, Tomos Thomas, Kan-Hua Lee, Yahya AlSaleh, Vincenzo Giannini, Avi Braun, Josine Loo, Dries Vercruysse, Pol Van Dorpe, Benedikt Bläsi, Stefan A. Maier, N. J. Ekins-Daukes W double-layer ARC, but that these losses can be very small [17]. Motivated by these results, we investigate cylindrically-shaped Al NPs embedded in a double-layer ARC.…”

Enhanced Conversion Efficiency of III–V Triple-junction Solar Cells with Graphene Quantum Dots

“…To further increase the conversion efficiency it is necessary to enhance light absorption, increase carrier collection, or reduce the energy loss due to thermalization. Several strategies have been proposed to increase the conversion efficiency in III–V multi-junction solar cells3456. For example, a new material engineering technique has been developed for maintaining high thermal homogeneity at the wafer surface, which expands the bandgap engineering possibilities for improving the efficiency in III–V multi-junction solar cells4.…”

“…For example, a new material engineering technique has been developed for maintaining high thermal homogeneity at the wafer surface, which expands the bandgap engineering possibilities for improving the efficiency in III–V multi-junction solar cells4. Also, metal nanoparticles have been introduced on the illuminated surface of III–V multi-junction solar cells for producing strong light scattering and light trapping, which is beneficial for carrier generation in the absorbing region56. A 15% increase of conversion efficiency has been implemented by introducing Au nanoclusters on top of the III–V multi-junction solar cells5.…”