Banca de DEFESA: LEONARDO JOSÉ QUINTERO DA CUNA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LEONARDO JOSÉ QUINTERO DA CUNA
Date: 26/11/2026
TIME: 14:00
LOCAL: Santo André
TITLE:

Synthesis and Physical Properties Study of Halides Perovskites and Vanadium Oxides for Energy Applications

PAGES: 100
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUBÁREA: Física da Matéria Condensada
SPECIALTY: Estruturas Eletrônicas e Propriedades Elétricas de Superfícies; Interf. e Partículas
SUMMARY:

The development of semiconductor materials for solar-energy conversion depends on understanding and controlling their structural, optical, and electronic properties, as well along with the process involved in charge separation and transport. This work investigates two complementary families of materials: halide perovskites and vanadium oxides. For halide perovskites, the study examined how dimensionality (3D, 2D, and 1D) affects their optical and charge-transport properties. It also investigated lead-free Cs3Sb2X9 compounds and the interactions between CsPb(Br,I)3 quantum dots and silver nanoparticles. Alongside this work, vanadate bismuth (BiVO4) thin films were investigated as photoanodes for photoelectrochemical water oxidation, focusing on surface modification and the incorporation of metallic nanoparticles.

The first part focuses on BiVO4 thin-film photoanodes modified through surface fluorination followed by the incorporation of silver nanoparticles (AgNPs) using a layer-by-layer approach. The treatment preserved the monoclinic BiVO4 structure and improved its photoelectrochemical response under simulated solar irradiation. The optimized BiVO4_F_AgNPs electrode achieved a photocurrent density of approximately 0.64 mA cm-2 at 0.6 V versus Ag/AgCl, nearly twice that of the unmodified film. Electrochemical measurements and first-principles calculations provided complementary evidence of favorable interfacial energetics and electron extraction at the BiVO4/Ag interface.

The second part examines three-dimensional and two-dimensional hybrid halide perovskites, with particular attention to how the thin film morphology influence charge transport. The results point to the role of structural features in shaping transport pathways, particularly under low-bias conditions. The third part investigates the lead-free halide series Cs3Sb2Br9-xClx (x = 0, 3, 6, 9) using temperature-dependent neutron diffraction and optical spectroscopy. Neutron diffraction revealed preferential halide occupation at terminal and bridging sites, differences in structural behavior across the series, and changes in atomic displacements and lattice dynamics with composition and temperature. The optical measurements showed broad emission with large Stokes shifts, consistent with self-trapped exciton emission. Taken together, these results help establish links between local halide distribution, lattice dynamics, and excited-state relaxation. Finally, the interaction between CsPb(Br,I)3 quantum dots and AgNPs was studied using optical spectroscopy and theoretical calculations. Photoluminescence quenching varied with halide composition and excitation wavelength. The calculations also showed that interfacial coupling depends on the chemical termination of the nanocrystals. Overall, this work studies how composition, structural organization, surface chemistry, and interfacial interactions influence the properties of semiconductor materials relevant to solar-energy conversion.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Titular - Examinador(a) Interno ao Programa - 2249395 - THIAGO BRANQUINHO DE QUEIROZ
Membro Titular - Examinador(a) Externo ao Programa - 1939561 - FERNANDO HEERING BARTOLONI
Membro Titular - Examinador(a) Externo à Instituição - ARIANO DE GIOVANNI RODRIGUES - UFSCAR
Membro Titular - Examinador(a) Externo à Instituição - SUELEN DE CASTRO - UNIFEI - UNI
Membro Suplente - Examinador(a) Interno ao Programa - 1671599 - MARCOS DE ABREU AVILA
Membro Suplente - Examinador(a) Interno ao Programa - 1671688 - ANDRE SARTO POLO
Membro Suplente - Examinador(a) Externo à Instituição - MARCELOS LIMA PERES - UNIFEI - UNI