CAREER: Plasmon-mediated photo-absorption and carrier recombination dynamics in semiconductor/metal hybrid nano-systems

University Of North Carolina At Charlotte, Charlotte NC

Investigators

Abstract

In this project, funded by the Chemistry Division's Macromolecular, Supramolecular and Nanochemistry Program, Marcus Jones from the University of North Carolina at Charlotte is investigating how the interactions between nano-sized quantum dots and metal particles in the presence of light can be used to enhance the function of optoelectronic devices such as solar cells and light-emitting diodes (LEDs). Quantum dots are tiny semiconductors whose color depends on their size: larger particles appear redder than smaller ones. Metal nanoparticles can act as miniature antennas that channel light energy into or out of the quantum dots. This research program aims to unravel the complex interplay between nanoscale metals and semiconductors that could potentially enable technological advances such as thinner, more efficient solar cells and brighter LEDs. This work is also being integrated into a teaching and outreach program, which, in collaboration with the Charlotte Teachers' Institute, aims to educate local schoolteachers about the amazing world of nanoscale science and facilitates their participation in short term projects where they can do cutting-edge research for themselves. Inspired by the activities of the NSF ADVANCE initiative at UNC Charlotte, Marcus is also organizing a seminar series at UNC Charlotte, aimed at improving the retention of women in science, at which female science professionals are invited to discuss the challenges and rewards of being a woman in science. This research program aims to develop our understanding of the photo-absorption and emission effects caused by resonant coupling between excitons in quantum dots and surface plasmon modes in nanostructured metals. Acting like local antennae, surface plasmon resonances can enable efficient coupling of electromagnetic energy into or out of a chromophore. This can manifest as increased photoluminescence intensity, which is ascribed to either increased photo-absorption, or radiative recombination. The ability of coupled surface plasmon modes to capture and concentrate electromagnetic energy presents a tremendous opportunity to enhance the role of quantum dots in light harvesting or LED applications by improving multi-exciton generation yields, increasing biexciton emission efficiencies and eliminating fluorescence blinking. Unlike previous studies, this work is primarily focused towards understanding the effects of plasmonic coupling on the photo-absorption and carrier recombination rates of multi-excited quantum dots. A combination of single particle and newly developed ensemble techniques is being used to distinguish multi-exciton fluorescence dynamics occurring in fabricated hybrid nanosystems that have been designed to enable good control over exciton-plasmon interactions. Successful completion of the proposed research tasks will (i) establish the dependence of photo-absorption and radiative recombination rates on the distance between semiconductor and metal nanoparticles; (ii) resolve effects due to changes in quantum dot size, shape and composition; and (iii) identify the differences between photo-absorption and emission enhancements induced in single exciton versus charged and multi-exciton states.