Banca de DEFESA: FERNANDO VELCIC MAZIVIERO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : FERNANDO VELCIC MAZIVIERO
DATE: 18/03/2026
TIME: 15:00
LOCAL: Auditório do CCET
TITLE:

Halogenated Perovskites for Photovoltaic Applications: Compositional Investigation, Doping, and Development of Lead-Free Materials.

KEY WORDS:

Halide Perovskites; Solar Cells; Structural Synthesis and Modification; Optoelectronic Proprieties

PAGES: 129
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Físico Química Inorgânica
SUMMARY:

Halide perovskites have been considered one of the most important classes of materials for photovoltaic applications, showing significant advances over the last decades in terms of power conversion efficiency, optoelectronic properties, and compositional versatility, which enables the tuning of structural and electronic parameters for applications in solar devices. In this context, this thesis addresses in an integrated manner the theoretical foundations, literature review, and experimental development of perovskites applied to solar cells. Initially, the fundamental concepts related to electronic structure, optical properties, and the physical mechanisms involved in the operation of photovoltaic devices are discussed, providing the basis for the interpretation of the subsequent results. Subsequently, an overview of the evolution of perovskites in solar cells is presented, encompassing hybrid organic–inorganic systems, fully inorganic lead-containing compositions, and, more recently, lead-free alternatives, with emphasis on the challenges associated with stability and toxicity. In the experimental and theoretical context, bismuth doping at the B-site of CsPbI3 and CsPbBr3 perovskites was investigated through calculations based on Density Functional Theory (DFT), in which the computational study was employed to predict the band structure of the materials and subsequently validated by experimental characterizations. Bi incorporation promoted a significant reduction in the bandgap, reaching values of 1.79 eV, corresponding to a decrease of up to 30% compared to the undoped perovskites, in addition to expanding the absorption range in the UV–Vis spectrum. The doping also resulted in tolerance factor values closer to unity, indicating greater structural stability of the cubic phase. In the case of CsPbI3, the presence of the dopant contributed to the stabilization of the black phase in thin films for up to 60 min under high humidity conditions (>50%), indicating improved structural stability of the material. Structural modifications as well as the electronic and optical properties of the obtained materials were also evaluated. Finally, the development of the fully inorganic and lead-free perovskite CsMnBr2I as a photoabsorber material is explored. The compound exhibited a bandgap of 1.83 eV and evidence of phase mixing involving CsMnBr3 and CsMnI3 in approximately 10% of the crystalline fraction. Spectroscopic analysis indicated an octahedral splitting ΔO of 5778 cm-1 for the [MnX6]4- crystal field, characteristic of a weak crystal field and confirming the nephelauxetic effect associated with the covalent character of the Mn–X bond. The material was employed as a photoabsorbing layer in a photovoltaic device, resulting in a power conversion efficiency (PCE) of 0.77% in tests performed under a solar simulator. The results obtained contribute to a deeper understanding of the relationships between composition, structure, and properties in halide perovskites and support the development of more stable and environmentally suitable alternatives for solar applications.

COMMITTEE MEMBERS:
Presidente - 349770 - DULCE MARIA DE ARAUJO MELO
Interna - 2140775 - LIVIA NUNES CAVALCANTI
Externo ao Programa - 3491716 - ANGELO ANDERSON SILVA DE OLIVEIRA - UFRNExterna à Instituição - ARUZZA MABEL DE MORAIS ARAUJO - UFRN
Externo à Instituição - RODOLFO LUIZ BEZERRA DE ARAÚJO MEDEIROS - UFRN
Externa à Instituição - SILVIA LETICIA FERNANDES - UNESP