Energy Harvesting Applications and Spectroscopy of Nanocrystals

This dissertation discusses the optoelectronic properties and applications of two types of nanoparticles. In particular, photoluminescence characteristics and energy harvesting applications.;In the first part, time-resolved photoluminescence (TRPL) measurement technique is used to study the photoluminescence (PL) of a novel type of colloidal nanoparticles (core/shell quantum dots). One of the unique features of these quantum dots is that, unlike conventional type of core/shell quantum dots in which the change of the potential from the core region to shell region follows a step function, these quantum dots have a smoothly varied potential profile. One of the main purposes of having the smooth confinement potential is to reduce the Auger recombination rate in the quantum dots, which will in turn increase the PL efficiency. Time-resolved photoluminescence data of the smooth potential sample is presented with the comparison of the data from control sample which has the conventional step potential. Analysis of the TRPL data shows samples of two different types of potentials behave different. The data suggests that, firstly, besides Auger recombination, there can be defects emission in the step potential sample, which can be the reason of a lower quantum efficiency; secondly, a possible intraband Auger effect suppression can be observed in the smooth potential sample that can potentially lead to higher quantum efficiency.;In the second part, we investigate the application of rare-earth element based upconversion nanoparticles (UCNP) in organic/inorganic hybrid perovskite solar cells. The perovskite solar cells have many advantages over other types of solar cells, it is a promising candidate for the next generation commercial solar cells. Due the possession of unique energy levels, rare-earth element based upconversion nanoparticles have the ability of simultaneously absorbing near-IR photons and converting them to higher energy photons. We demonstrate the possibility of using upconversion nanoparticles to improve the power conversion efficiency of the perovskite solar cells by increasing their spectral response in the near-IR wavelength range. We show different approaches of incorporating the UCNP into the perovskite solar cell structure and their results. We also show a straightforward method of tuning the perovskite film morphology by controlling the ratio of different lead salts in the precursor solution. Maximum PCE of 9.5% of the perovskite solar cell devices fabricated by the mixed lead salt precursors is achieved.