Photon energy upconversion through thermal radiation with the power efficiency reaching 16%

Abstract

The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb 3 þ -doped ZrO 2 . By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

Near-Infrared Emission and Photon Energy Upconversion of Two-Dimensional Copper Silicates

“…Practically both processes could occur under laser excitation, and thus the two mechanisms are not easily distinguishable from the emission spectra. Since the emission spectra can be successfully fitted by the law of black body radiation, it is reasonable to suggest that laser driven thermal radiation may be dominating, especially under high powder laser excitation.To evaluate the efficiency of white light generation, we have made a systematical comparison of the efficiency for the copper silicates and other compounds reported to show highly efficiency white light thermal radiation (such as ZrO 2 :Yb 3+ and Yb 2 O 3 )16,33 . As shown inFig.…”

Efficient upconversion luminescence from Ba5Gd8Zn4O21:Yb3+, Er3+ based on a demonstrated cross-relaxation process

“…In view of the unique optical properties, UC luminescence (UL) materials doped with rare earth (RE) ions have been utilized in potential applications, such as biological diagnosis, data storage, solar cells, solid display technique, solid-state lasers, and sensor technology23456789101112. However, one outstanding roadblock still exists: most of the UL materials fail to produce strong optical emission under low excitation power, which greatly limits the practical application in different fields.…”

“…Paradoxically, further increasing the laser power may cause marked overheating effects, which can lead to possible scalding of animal tissue upon continuous irradiation89. Moreover, infrared solar photons with wavelength greater than 1 μm are unabsorbed by solar cells working in the visible and near-infrared regions, thus UL materials provide a solving method by turning infrared solar photons into visible photons, leading to increased photoelectric conversion efficiency of the solar cells in theory1112. However, sun-light is usually not sufficiently strong to activate the UC process.…”

Transition Metal‐Involved Photon Upconversion

“…There is another distinct UC process of thermal radiation when sensitised by TM ions in Cu 2+ ‐ or Cr 3+ ‐doped ZrO 2 54. This is a type of UC process that absorbs NIR sunlight or laser energy, resulting in a temperature increase of the material's body through multiphonon relaxation, followed by release via thermal radiation, such as the blackbody radiation, as illustrated in Figure 15 .…”