Banca de DEFESA: ARIANY BONADIO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ARIANY BONADIO
DATE: 06/11/2023
TIME: 13:30
LOCAL: Santo André
TITLE:

Advances in Hybrid Halide Perovskites: Structural Phase Control, Dimensionality/Morphology Changes, and 2D Perovskite Integration towards Solar Cell Applications

PAGES: 120
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:

Methylammonium lead iodide (MAPbI₃) is an important light-harvesting semiconducting material with excellent optical and electronic properties to be used in optoelectronic devices. We have worked on three important scientific aspects involving MAPbI₃: (1) a study of structural phase transition on three-dimensional (3D) MAPbI₃ and stabilization of cubic phase below room temperature; (2) the water-assisted dissolution-recrystallization process of MAPbI₃ involving change in morphology/dimensionality and also a magnetic doping strategy; and (3) study of two-dimensional (2D) perovskites and application in perovskite-based solar cell devices. First, we produced MAPbI₃ via a facile solution method. Electrical resistivity measurements suggest that the conduction mechanism in perovskites is governed by mixed electronic and ionic species, including iodine interstitials or interstitial hydrogen impurities. To address the challenge of mixed electronic-ionic charge carriers that can lead to material degradation, a strategy was suggested to shift the structural phase transition and stabilization of the high-symmetry cubic phase below room temperature through long thermal annealing. The high-entropy disordered organic molecules are quenched and become kinetically trapped in the cubic phase. We propose a new phase diagram for this important MAPbI₃ system combining different structural phases as a function of temperature with annealing time. Our results provide a unique opportunity to evaluate the physical properties of both cubic and tetragonal phases of MAPbI₃ at the same temperature eliminating phonon effects. Besides higher electrical resistivity, the perovskite cubic phase presents a faster charge carrier lifetime than the tetragonal phase and partial PL quenching, pointing toward increased trap-assisted nonradiative recombination.

            Second, we study the dissolution-recrystallization process of MAPbI₃ that leads to the conversion of cuboid-shaped (3D) to microwire (1D) morphology. A 1D monohydrate microwire formed first during this process present a monoclinic structure with 1D chains of [PbI₆]^4- octahedra. Importantly, these microwires can be reversed to MAPbI₃ crystal structure through heat treatment or in an evacuated atmosphere. The 1D chains are formed by the iodide ions shared by the edges of the [PbI₆]^4- ions and are stabilized by the presence of both water and MA, forming big channels between chains. We have used this alternative self-assembly process as a strategy for introducing magnetic Fe³⁺/Fe²⁺ ions into the perovskite structure, opening new avenues for doping and potential applications in magneto-electronic devices. From first principles calculations, we determined that Fe²⁺ ions are localized in the interstitial site while Fe³⁺ ones are substitutional on Pb sites. The very high mobility and static dielectric constant, achieved by photogenerated charge carriers in MAPbI₃, are suppressed with Fe doping. These results are discussed based on a non-radiative recombination process assisted by phonons that is activated by the inclusion of the Fe ions leading to a quenching of the photoluminescence emission peak.

            Third, the study extends to the synthesis of highly stable 2D perovskites based on π-conjugated ligands and their influence on 2D/3D perovskite heterostructures, particularly for applications in perovskite solar cells. A novel 2D perovskite, (TP-TEA)₂MA_n-1Pb_nI_3n+1, is synthesized using π-conjugated thieno-pyrrole molecule as a ligand. This new ligand enhances the stability of 2D perovskites, offering long-term protection against ion mobility and moisture. We also fabricated 2D/3D heterostructures, demonstrating more efficient interface charge transfer and reduced nonradiative recombination rates, which enhance the stability and performance of perovskite solar cells.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Titular - Examinador(a) Externo ao Programa - 1939561 - FERNANDO HEERING BARTOLONI
Membro Titular - Examinador(a) Externo ao Programa - 1652541 - LETICIE MENDONCA FERREIRA
Membro Titular - Examinador(a) Externo à Instituição - ADILSON JESUS APARECIDO DE OLIVEIRA
Membro Titular - Examinador(a) Externo à Instituição - CARLOS FREDERICO DE OLIVEIRA GRAEFF - UNESP
Membro Suplente - Examinador(a) Interno ao Programa - 1544341 - WENDEL ANDRADE ALVES
Membro Suplente - Examinador(a) Interno ao Programa - 1671275 - DERVAL DOS SANTOS ROSA
Membro Suplente - Examinador(a) Interno ao Programa - 1671688 - ANDRE SARTO POLO
Membro Suplente - Examinador(a) Externo ao Programa - 3066318 - JULIAN ANDRES MUNEVAR CAGIGAS
Membro Suplente - Examinador(a) Externo à Instituição - MARCELOS LIMA PERES - UNIFEI - UNI