resumo
YbIII-doped phosphors are promising near-infrared (NIR) emitters for telecommunications and energy conversion. The quantum cutting mechanism, where one high-energy photon yields two (or more) lower-energy photons, is often used to improve the YbIII luminescence. While YbIII quantum cutting has mainly been studied in matrices such as oxides, this work aims to investigate its contribution to molecular systems. For that, the 1D coordination polymer [Ln(tfa)3(mu-dppeo)]n (tfa- = trifluoroacetylacetonate, dppeo = [(diphenylphosphoryl)ethyl](diphenyl)phosphine oxide, Ln = YbIII/TbIII) was synthesized. Luminescence was investigated by varying the TbIII/YbIII ratio, analysing emission under different excitation powers, and modelling excited-state dynamics. The materials exhibit visible TbIII luminescence (quantum yield: 45%) and NIR YbIII emission (quantum yield: similar to 1%). Upon ligand excitation, TbIII-to-YbIII energy transfer (ET) competes with ligand-to-YbIII ET to populate the YbIII 2F5/2 level, favouring its luminescence. The sub-unit slope in the log-log dependence of the YbIII emission intensity on the excitation power, supported by simulations, indicates a two-photon emission process. This behaviour aligns with a cooperative quantum cutting mechanism, which competes with the conventional downshifting luminescence driven by ligand-to-YbIII ET. The quantum cutting contribution is initiated by the ligand-centred absorption, followed by ET to TbIII and subsequently to two YbIII centres. These findings offer insights into enhancing YbIII luminescence in complexes and provide a design framework for advanced materials aimed at energy conversion.
categoria
Materials Science; Physics
autores
Bispo-Jr, AG; Saraiva, LF; Neto, ANC; Coelho, SFN; Mazali, IO; Carlos, LD; Sigoli, FA
nossos autores
Albano Neto Carneiro Neto
Investigador Júnior
Luís Carlos
Professor CatedráticoProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
The authors are thankful to FAPESP 2021/06326-1; 2021/0811-2 and INCT/INOMAT-National Institute of Science Technology in Complex Functional Materials (CNPq: 465452/2014-0 and FAPESP: 2014/50906-9). AGBJ thanks the Support Program for New Faculty at USP from PRPI-USP. FAS thanks to CNPq (304807/2022-2 and 304564/2018-4). AGBJ also thanks FAPESP (2019/23763-6 and 2021/09755-0) for the award of a postdoctoral scholarship. LFS also thanks FAPESP (2023/05718-9) for the award of a doctorate scholarship. This work was partially developed under the project CICECO-Aveiro Institute of Materials UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by funds through the FCT/MEC (PIDDAC). Professor Lazaro Aurelio Padilha Junior is acknowledge for his assistance in measuring the pump power dependency of the emission spectra. Photonic Materials Laboratory of Institute of Chemistry-UNESP-is acknowledged for the assistance with the PLQY measurements.