Banca de DEFESA: LEONARDO CLEMENTE EMIDIO DE BARROS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LEONARDO CLEMENTE EMIDIO DE BARROS
DATE: 26/07/2023
TIME: 09:30
LOCAL: Defesa Remota - https://meet.google.com/kev-wvwi-jri
TITLE:

NaYF 4 nanoparticles co- and tri-doped as UV/visible to infrared light converters targeting use in solar cells

KEY WORDS:

Nanoparticles. Rare-earth ions. Silicon solar cells.

PAGES: 69
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

The urgent need for clean and sustainable energy sources has driven research into the
development of technologies that generate energy from renewable sources, as in the case
of solar cells (SCs) that convert sunlight into electrical energy. However, the efficiency of
these types of devices is still relatively low, as occurs in silicon-based SCs, in which the
region where they are most efficient (infrared-IR) the solar emission is lower, when
compared to the emissions of the Sun that occur in the UV-visible. Thus, the objective of
this study was to investigate combinations of ions, mainly rare earth (REs), capable of
converting high energy photons (UV-Visible) into low energy photons (in the IR region,
around 980 nm) in order to increase the efficiency of silicon solar cells. Therefore, the main
objective was to investigate the luminescent properties of nanoparticles (NPs) doped with
REs and other ions and their potential to convert photons from UV-Visible to IR. In this
study, the following ions were used: Yb 3+ (Ytterbium), Er 3+ (Erbium), Nd 3+ (Neodymium), Ce 3+
(Cerium), Gd 3+ (Gadolinium), Mn 3+ (Manganese) and Tm 3+ (Thulium). The optical
characterizations of the synthesized NPs occurred by obtaining excitation and emission
spectra. NPs doped with two and three ions were used. The idea was to find which ions
could absorb photons with wavelengths in the UV-visible region and transfer their energy to
Yb 3+ ion, thus generating emissions in the IR (~980 nm). As results, in general, it was
obtained that the codoped NPs (X 3+ ,Yb 3+ ) presented efficient energy transfers (ETs) between
the chosen X 3+ ions and the Yb 3+ . However, in the sample co-doped with Mn 3+ and Yb 3+ , ET
was not evidence, although Mn 3+ had shown intense absorption in the desired region.
Regarding the tridoped samples doped (X 3+ ,Nd 3+ ,Yb 3+ ), the inclusion of the Nd 3+ ion as an
intermediary for the ET between some chosen X 3+ ion and the Yb 3+ , did not prove to be
advantageous, since it resulted in a decrease in the Yb 3+ emission. However, when Nd 3+ was
combined with Ce 3+ and Yb 3+ ions, the system showed a wide absorption region within the
desired spectrum (300 to 600 nm), proving to be an interesting system for future studies. In
short, the results obtained here indicate that NPs doped with RE 3+ ions have the potential to
improve the efficiency of silicon SCs, however, this possibility still needs to be thoroughly
investigated.

BANKING MEMBERS:
Presidente - 1545463 - CARLOS JACINTO DA SILVA
Interno(a) - 1695829 - ANDRE DE LIMA MOURA
Externo(a) ao Programa - 092.012.634-06 - TASSO DE OLIVEIRA SALES - UFAL
Externo(a) ao Programa - 2579019 - WAGNER FERREIRA DA SILVA
Externo(a) à Instituição - ANDRESSA NOVATSKI