Transferência de energia ressonante entre pontos quânticos, zinco ftalocianina e praseodímio

Abstract

In the present work the energy transfer processes between semiconductor quantum dots (QDs) were investigated through computer simulations and microluminescence surface scan technique (MSST) measurements. It was simulated, and measurements were performed in cadmium selenide covered with zinc sulfide (CdSe/ZnS) quantum dots. Initially, it was written the Hamiltonian for two and three quantum dots coupled through Förster potential. The Förster potential describes the energy transfer through a dipole interation, without charge transfer, since the two particles have energy levels in resonance. It was simulated the average occupation of each state of the Hamiltonian, using the average occupation simulations it was found the values of energy laser, laser power and quantum dots detunning that favor the population of each Hamiltonian state. Using the found values it was also possible to simulate the Hamiltonian time evolution, in the simulations where a continuous wavelength (cw) laser or a pulsed laser excites the system. In the experimental section it was studied the energy diffusion of QD-QD, QD-Zinc phthalocyanine (ZnPc) systems, and between praseodymium ions. For this purpose, photoluminescence, optical absorption, and microluminescence scan surface were applied. The MSST allows the direct measurement of energy diffusion length, alternatively to time resolved measurements. The simulations had shown the best set of parameters, such as laser and quantum dots detunning increase the population of each Hamiltonian state. For the system consisting of a linear chain of three quantum dots was possible to find the best set of parameters for maximum energy migration along the chain. In the experimental section it was observed the dependence of the diffusion length with the concentration of QDs, an evidence of FRET couppling, the same observation also on praseodymium samples. It also noted the energy transfer between QDs of different sizes.