The potential of transparent sputtered NaI:Tm2+, CaBr2:Tm2+, and CaI2:Tm2+thin films as luminescent solar concentrators

Autor: Maarten P. Plokker, Evert P.J. Merkx, Erik van der Kolk
Rok vydání: 2021
Předmět:
Zdroj: Solar Energy Materials and Solar Cells. 223:110944
ISSN: 0927-0248
DOI: 10.1016/j.solmat.2020.110944
Popis: The parameters governing the performance of a luminescent solar concentrator (LSC) are determined for sputtered thin-films of NaI:Tm 2 + , CaBr 2 :Tm 2 + , and CaI 2 :Tm 2 + . These parameters are determined by using six gradient thin film material libraries, combinatorially sputtered from metallic and pressed powder targets. These films show strong 4 f 13 → 4 f 12 d 1 absorption of maximally 752 cm − 1 at.% − 1 for NaI:Tm 2 + , 31 cm − 1 at.% − 1 for CaBr 2 :Tm 2 + , and 473 cm − 1 at.% − 1 for CaI 2 :Tm 2 + . This absorption covers the entire visible spectrum and does not overlap with the infrared 4f-4f emission at 1140 nm. Decay measurements are used to estimate the quantum yields of the thin-films. These quantum yields can be as high as 44 % for NaI:Tm 2 + , when doped with 0.3 at.% Tm. Even at doping percentages as low as 0.3 at.%, the films appear to show luminescence quenching. The concentration-dependent absorption and quantum yield are combined with the index of refraction, resolved from transmission measurements, to simulate the optical efficiency of a thin film Tm 2 + -doped halide LSC. These simulations show that LSCs based on Tm 2 + can display excellent color rendering indices of up to 99 %, and neutral color temperatures, between 4500K and 6000K. Under optimal conditions, thin-films constrained to a thickness of 10 μ m and 80 % transmission of the visible spectrum, would be able to display optical efficiencies of 0.71 %. This optical efficiency compares favorably to the maximally achievable 3.5 % under these constraints. This efficiency is largely independent of the size of LSC itself.
Databáze: OpenAIRE
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