(262h) Exciton Dissociation and Charge Carrier Generation At Core/Shell Heterojunction in Quantum Dots

Electron-hole pairs (excitons) are generated by photoexcitation of electrons to excited electronic states. Exciton dissociation and generation of free charge carriers is central for light-harvesting applications of photoactive nanoparticles. This talk will focus on computational investigation of effect of heterojunctions on exciton dissociation in core/shell quantum dots. It has been shown in various experimental studies that presence of heterojunctions in nanocrystals can greatly facilitate exciton dissociation. This study will present the following four computed properties: (1) exciton binding energy, (2). electron-hole recombination probability (3). electron-hole separation distance and (4).electron-hole pair density as metrics for analyzing effect of core/shell structures in nanocrystals. Results for CdSe/ZnS core/shell quantum dots will be presented for a series of dots sizes. Effect of dot size and thickness of the shell of exciton dissociation will be presented and comparison with experimental results will be discussed. The electron-hole interaction energy is quantified by calculating the exciton binding energy and the spatial distribution of the charge carrier in the quantum dot is analyzed by electron-hole pair density functions. The local environment of the electron and hole quasiparticles in the quantum dot is probed using the average electron-hole separation distance and the electron-hole recombination probability. Exciton dissociation is a complex process and the four metrics mentioned above provide a multi-faceted description of this phenomenon.