TY - JOUR
T1 - Strongly enhanced upconversion in trivalent erbium ions by tailored gold nanostructures: Toward high-efficient silicon-based photovoltaics
AU - Christiansen, Jeppe
AU - Vester-Petersen, Joakim
AU - Roesgaard, Søren
AU - Møller, Søren H.
AU - Christiansen, Rasmus E.
AU - Sigmund, Ole
AU - Madsen, Søren Peder
AU - Balling, Peter
AU - Julsgaard, Brian
PY - 2020
Y1 - 2020
N2 - Upconversion of sub-band-gap photons constitutes a promising way for improving the efficiency of silicon-based solar cells beyond the Shockley-Queisser limit. 1500 nm to 980 nm upconversion by trivalent erbium ions is well-suited for this purpose, but the small absorption cross section hinders real-world applications. We employ tailored gold nanostructures to vastly improve the upconversion efficiency in erbium-doped TiO thin films. The nanostructures are found using topology optimization and parameter optimization and fabricated by electron beam lithography. In qualitative agreement with a theoretical model, the samples show substantial electric-field enhancements inside the upconverting films for excitation at 1500 nm for both s- and p-polarization under a wide range of incidence angles and excitation intensities. An unprecedented upconversion enhancement of 913 ± 51 is observed at 1.7 W cm−2. We derive a semi-empirical expression for the photonically enhanced upconversion efficiency, valid for all excitation intensities. This allows us to determine the upconversion properties needed to achieve significant improvements in real-world solar-cell devices through photonic-enhanced upconversion.
AB - Upconversion of sub-band-gap photons constitutes a promising way for improving the efficiency of silicon-based solar cells beyond the Shockley-Queisser limit. 1500 nm to 980 nm upconversion by trivalent erbium ions is well-suited for this purpose, but the small absorption cross section hinders real-world applications. We employ tailored gold nanostructures to vastly improve the upconversion efficiency in erbium-doped TiO thin films. The nanostructures are found using topology optimization and parameter optimization and fabricated by electron beam lithography. In qualitative agreement with a theoretical model, the samples show substantial electric-field enhancements inside the upconverting films for excitation at 1500 nm for both s- and p-polarization under a wide range of incidence angles and excitation intensities. An unprecedented upconversion enhancement of 913 ± 51 is observed at 1.7 W cm−2. We derive a semi-empirical expression for the photonically enhanced upconversion efficiency, valid for all excitation intensities. This allows us to determine the upconversion properties needed to achieve significant improvements in real-world solar-cell devices through photonic-enhanced upconversion.
KW - Upconversion of sub-band gap photons
KW - High-efficient photovoltaics
KW - Photonic enhancement
KW - Topology optimization
U2 - 10.1016/j.solmat.2020.110406
DO - 10.1016/j.solmat.2020.110406
M3 - Journal article
SN - 0927-0248
VL - 208
JO - Solar Energy Materials and Solar Cells
JF - Solar Energy Materials and Solar Cells
M1 - 110406
ER -