Strongly enhanced upconversion in trivalent erbium ions by tailored gold nanostructures: Toward high-efficient silicon-based photovoltaics

Abstract

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 2 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 an excitation intensity of 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.

Compact 200 line MATLAB code for inverse design in photonics by topology optimization: tutorial

“…In recent work [28], it was demonstrated that using a refractive index and extinction cross-section-based non-linear material interpolation yielded significantly improved results when designing Au, Ag, and Cu nano-particles for localized field enhancement, with recent applications to enhanced upconversion [29], thermal emission [30], and Raman scattering [31]. This interpolation function avoids artificial resonances in connection with the transition from positive to negative ε values and reads Fig.…”

Inverse design in photonics by topology optimization: tutorial

“…The reader may solve the problem in Eq. (19), using a continuation of the β values, by executing the study named Continuation in the model MetalensCase3.mph. Hereby the field,ξ(r), shown in Fig.…”

“…Besides the above change to the FOM, the optimization problem being solved remains the same as in Eq. (19). The reader may solve the new problem by executing the study named Continuation in the model MetalensCase4.mph.…”

“…Indeed, the main challenge when applying TopOpt is often to limit the design freedom offered by the method, in a way that conforms with fabrication constraints. Within photonics and plasmonics, TopOpt has received increasing attention over the last two decades [8,10] with recent examples of applicationss including the design of dielectric multiplexers [11], dielectric metalenses [12][13][14], extreme dielectric confinement structures [15,16], plasmonic nano-antennas [17], and plasmonic nanoparticles for solar cell 0740-3224/21/020496-14 Journal © 2021 Optical Society of America applications [18,19] and for enhanced thermal emission [20] and Raman scattering [21], to name but a few.…”

Synthesis of upconversion TiO2:Er3+-Yb3+ nanoparticles and deposition of thin films by spin coating technique

“…Application of upconversion luminescent nanoparticles composed of lanthanide ions doped inorganic host material as spectrum modifier have attracted great interest due to their outstanding luminescent properties, which are potentially used in laser materials, medical [1] and photovoltaic [2] applications. In recent years, semiconductor metal oxides (TiO 2 , SnO 2 , ZnO, In 2 O 3 ) have been widely used as host materials due to their high thermal and chemical stability, and suitability in many applications such as photocatalysis [3], sensor devices [4], and optical devices [5].…”