Time Dependent Study of Multiple Exciton Generation in Nanocrystal Quantum Dots

Progress in Non-equilibrium Green's Functions

Damtie, Fikeraddis A.^1 ; Wacker, Andreas^1

Mathematical Physics, Lund University, Sweden^1

关键词: Conservation of momentum;    Excitation parameters;    Experimental conditions;    High-energy excitons;    Multiple exciton generations;    Nanocrystal quantum dots;    Quantum rate equations;    Recombination process;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/696/1/012012/pdf
DOI  :  10.1088/1742-6596/696/1/012012

来源: IOP

【 摘 要 】

We study the exciton dynamics in an optically excited nanocrystal quantum dot. Multiple exciton formation is more efficient in nanocrystal quantum dots compared to bulk semiconductors due to enhanced Coulomb interactions and the absence of conservation of momentum. The formation of multiple excitons is dependent on different excitation parameters and the dissipation. We study this process within a Lindblad quantum rate equation using the full many-particle states. We optically excite the system by creating a single high energy exciton ESXin resonance to a double exciton EDX. With Coulomb electron-electron interaction, the population can be transferred from the single exciton to the double exciton state by impact ionisation (inverse Auger process). The ratio between the recombination processes and the absorbed photons provide the yield of the structure. We observe a quantum yield of comparable value to experiment assuming typical experimental conditions for a 4 nm PbS quantum dot.