Banca de DEFESA: ELIANE APARECIDA MORAIS
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : ELIANE APARECIDA MORAIS
DATE: 29/05/2025
TIME: 09:30
LOCAL: Auditório 801 no 8º andar do Bloco B do Campus de Santo André da Universidade Federal do ABC
TITLE:
Anion-exchange and reducing dimensionality in halide perovskites towards UV emission
PAGES: 100
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUBÁREA: Física da Matéria Condensada
SPECIALTY: Prop. Óticas e Espectrosc. da Mat. Condens; Outras Inter. da Mat. com Rad. e Part.
SUMMARY:
Metal halide perovskites are promising candidates for application in photovoltaic devices and light-emitting diodes (LEDs). They have excellent optoelectronic properties, including high photoluminescence quantum yield (PLQY) and tunable direct bandgaps. The light-emitting device using this perovskite family with high efficiency could be used in interdisciplinary fields. For instance, UV light has been used to inactivate germs such as bacteria and viruses and has a significant effect on disinfecting surfaces. The biggest challenge nowadays is to synthesize these materials with emission in the UV region through size effect, doping, or changing dimensionality. Thus, in this thesis, we have systematically studied two semiconducting families of halide perovskites: (1) all inorganic 3D quantum dots and (2) 2D layered Ruddlesden-Popper. In the first part the all inorganic CsPbX3 halide perovskites in the form of quantum dots (QDs) with X = I-, Br-, Cl-, and F- were investigated. The importance of this study consists in the systematic method to evaluate the optoelectronic properties by using the anion exchange strategy. Structural and morphological characterizations indicated that all the QDs samples were successfully synthesized through hot injection routes. As Cl- ions are introduced into the perovskite structure, the unit cell volume and lattice parameters decrease, the band gap energy increases, and a blue shift is observed in the photoluminescence spectrum. Further addition of F- ions, which have higher electronegativity and smaller ionic radius, leads to an improvement in PLQY, but the UV shift is not observed. In the second part of the thesis, we present the results of the 2D (M)2MAn-1PbnX3n+1 halide perovskites counterparts, with X = I-, Br-, Cl-; MA+ = methylammonium and M = n-butylammonium, phenylethylamine, and phenylmethylamine. The organic molecules (M) act as a spacer between n [PbX6]4- octahedral layers. The results indicate that the inorganic layers show a strong quantum confinement effect, enlarging the band gap energy and shifting the PL emission peak to UV region. In this context, a systematic study involving the synthesis and physical properties is presented for these 2D materials. By varying the halide anion from I- to Br- and Cl- in (BA)2PbX4, we observe a UV shift, where the perovskite (BA)2PbCl4 showed emission at 357 nm. Most important, it was observed an unusual phenomenon in the latter compound. This BA-based perovskite displays conduction band spin-splitting which gives rise to the Rashba effect. As a result, the photoluminescence emission is almost extinguished, and a very slow PLQY is observed. Such a discovery limits this material from being applied as a light emitter. In the last part of the thesis, a study of PLQY correlated with temperature is presented for the perovskite (BA)2PbBr4, where it was observed that by increasing the temperature during the synthesis, the PLQY of this sample increases. The results described in this thesis represent a new perspective for the scientific community of semiconductors and will pave the way for a new route towards the relationship between structural and optical properties, providing a better understanding for application in optoelectronic devices.
COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Titular - Examinador(a) Externo ao Programa - 3420345 - CARLOS AUGUSTO MERA ACOSTA
Membro Titular - Examinador(a) Externo ao Programa - 1864481 - HUEDER PAULO MOISES DE OLIVEIRA
Membro Titular - Examinador(a) Externo à Instituição - MARCELOS LIMA PERES - UNIFEI - UNI
Membro Titular - Examinador(a) Externo à Instituição - MARCIO PERON FRANCO DE GODOY - UFSCAR
Membro Suplente - Examinador(a) Interno ao Programa - 1707133 - ISELI LOURENCO NANTES
Membro Suplente - Examinador(a) Interno ao Programa - 1671275 - DERVAL DOS SANTOS ROSA
Membro Suplente - Examinador(a) Externo à Instituição - FELIX GUILLERMO GONZALEZ HERNANDEZ - USP