Understanding Photoluminescence Quantum Yield In Cesium Lead Tribromide Nanocrystals

Semiconducting nanoparticles have played a pivotal role in advancing optoelectronic technologies. The photoluminescence quantum yield (PLQY), which measures emitted photons relative to absorbed photons, stands as a critical performance metric for these materials, directly influencing device performance. In the case of CsPbX3 (X = Cl^-1, Br^-1 , I^-1 ) nanocrystals (NCs), the electronic structure is determined through the interactions of molecular orbitals within the PbX6^-1 repeating unit. The most prevalent crystal defect in these materials is halide vacancies, which can locally confine excited carriers, resulting in carrier relaxation through non-radiative recombination mechanisms. This dissertation focuses on understanding the formation of electronic traps within CsPbBr3 NCs and designing effective strategies to mitigate their impact and occurrence. Chapter 2 introduces two precise PLQY measurement methods for colloidal solutions: one compares emission spectra to a reference standard, and the other outlines a custom integrating sphere setup. This chapter provides comprehensive guidance for accurate PLQY measurement, with a particular focus on CsPbBr3 NCs, given that their absorption and emission properties influence PLQY measurement design. Chapter 3 delves into the design of saturated ligand solutions (SLSs), which I propose as a better solvent system for CsPbBr3 NCs. This endeavor involves a series of iterations with the SLSs formulation to identify specific ligand species conducive to optimal surface trap passivation. Our unique approach to the SLS preparation process enables the introduction of substantial quantities of ligands, previously unachievable through direct ligand addition. Concurrently, the SLSs facilitate continuous dilution of the colloidal solution without compromising the structural and optoelectronic quality of the NCs, addressing a significant field limitation. These methods present novel opportunities to gain insights into ligand interactions within perovskite systems and offer tailored solutions designed for perovskite materials. Lastly, Chapter 4 demonstrates the potential to limit the impact of electronic trap states in CsPbBr3 NCs when they are incorporated into solution-phase superlattices. Superlattices enable enhanced interparticle electronic coupling interactions due to the close proximity of individual NCs. This results in a more delocalized electronic structure and improved radiative recombination efficiency, offering insights into strategies for enhancing radiative recombination and outcompeting the kinetics of non-radiative electronic processes.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemistry

Grantor

Texas A&M University

Year dc:date.issued

2023

Author dc:creator

• Mireles Villegas, Noel

Advisor dc:contributor.advisor

• Sheldon, Matthew T

Committee members dc:contributor.committeemember

• Banerjee, Sarbajit
• Yan, Xin
• Belyanin, Alexey

• Nanocrystals
• Perovskite
• Photoluminescence Quantum Yield
• Surface Chemistry
• Materials Characterization
• Optoelectronic
• Superlattices

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/1969.1/203081

OAI record oai:identifier

https://oaktrust.library.tamu.edu/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aoaktrust.library.tamu.edu%3A1969.1%2F203081