Energy Conversion at the Nanoscale

Abundant renewable energy is essential to maintain adequate living standards for a growing global population. This thesis explores how semiconductor nanocrystals can harvest sunlight and convert it into useful forms of energy, such as electricity, light, and chemical fuels. The thesis is structured as follows. Chapter 1 elaborates on the motivation for this research, and Chapter 2 provides the background necessary to understand the following research-based chapters. Chapters 3 and 4 present the longest study to date of semiconductor nanocrystals in luminescent solar concentrators (LSCs), a photovoltaic technology that can reconcile urban constructions and energy generation in the same space. Specifically, Chapter 3 analyzes the outdoor performance of five LSCs over a full year, and Chapter 4 investigates the second year of data and the post-mortem analysis of the LSCs. Notably, CuInS₂- and InP-based nanocrystals withstand outdoor exposure successfully due to a synergistic effect with the embedded photoactive polymer. Chapter 5 dives deeper into the stability of InP-based QDs, systematically studying how the photon flux, photon energy, and the atmospheric composition influence their luminescence. The results indicate that traces of oxygen are sufficient to cause irreversible photodarkening of the QDs, a process determined by the cumulative photon dose absorbed. Chapter 6 focuses on resolving the excited-state dynamics of heavy-metal-free Cu₂₋ₓ/CuInS₂ heteronanocrystals, a necessary step for assessing their potential for light-harvesting applications. The findings highlight both the promise (µs-lived excited state) and the challenges (traps) present in Cu₂₋ₓ/CuInS₂ heteronanocrystals as well as single-composition Cu₂₋ₓ and CuInS₂ nanocrystals. Chapters 7-10 summarize the main findings and discuss the future prospects of the research line in English, Dutch, Catalan, and Spanish.