Charge Carrier Dynamics in Interconnected Halide Perovskite Quantum Dot Networks

• Autores: David Otto Tiede
• Directores de la Tesis: Hernán Ruy Míguez García (dir. tes.), Juan Francisco Galisteo López (dir. tes.)
• Lectura: En la Universidad de Sevilla ( España ) en 2024
• Idioma: inglés
• Número de páginas: 182
• Enlaces
  • Tesis en acceso abierto en: Idus
• Resumen

  • Semiconductor materials are integral to modern technology, with their usage predicted to increase significantly. This rise in demand, coupled with resource scarcity and the need for optimized energy usage, necessitates more efficient optoelectronic devices. Understanding charge carrier dynamics in semiconductors is crucial for addressing these challenges. Perovskite quantum dot (QD) solids are emerging as promising semiconductor materials due to their excellent optoelectronic properties, nanostructuring advantages, and quantum confinement effects, making them ideal for next-generation devices. However, the isolation needed for quantum confinement contrasts with the need for charge injection or extraction in many optoelectronic devices. This interplay between confinement and transport effects on carrier recombination in QD networks involve significant experimental and fundamental challenges, which hinders systematic studies. This thesis aims to comprehensively study charge carrier cooling, trapping, and recombination dynamics in perovskite QD solids over time scales from femtoseconds to milliseconds, with varying connectivity. We developed a method using macroscopic time-resolved spectroscopy to distinguish between local (isolated) and global (connected) recombination dynamics. This method allows the application of density-dependent recombination models to complex material systems, accounting for time-dependent effects like diffusion. Through this characterization, we analyzed how QD connectivity affects macroscopic optoelectronic properties such as emission yield and emission linewidth. Our findings indicate that different degrees of connectivity are optimal for different applications, providing a roadmap for screening material parameters for specific optoelectronic devices. We also investigated charge carrier relaxation processes in connected QD solids, showing that interparticle coupling significantly influences relaxation pathways and that multiparticle effects like Auger reheating can slow cooling dynamics. We found that Auger effects depend not only on nanocrystal size but also on the surrounding environment. In ligand-free QD solids, we observed that excitonic species interact strongly with a continuum of unbound states, indicating a hybrid of excitonic and free carrier behavior. In ligand-based colloidal QDs, which are well separated, we demonstrated energy transport mediated through dipole coupling on various length scales. On a few nanometer scale, exciton-exciton interaction tuning in closely packed QDs enables dipole-mediated diffusion, quenching fast intradot Auger processes while enhancing interdot Auger processes through diffusion. On a macroscopic scale, dipole coupling with optical resonators in microcavities causes exciton-polariton formation, leading to delocalized recombination dynamics. We showed that strong light-matter coupling in a confined optical potential can achieve exciton-polariton condensation, marking the first demonstration of room-temperature condensation in QD solids. This discovery lays the groundwork for a new technology platform with significant implications for polariton-driven applications. In conclusion, this thesis enhances the understanding of charge carrier dynamics in interconnected QD solids. We hope it provides valuable insights for efficiently exploiting this promising material system in various optoelectronic devices.