Spectroscopic properties of semiconductor nanoparticles (NPs) exhibit a strong dependence on the shape and size of the NPs. At finite temperatures, the NPs exists in an ensemble of structures and inclusion of these structures is essential for accurate theoretical investigation of the optical properties of these materials. However, performing ensemble-averaged calculations using conventional electronic structure theories prohibitive because of steep computational cost. In this work, we present a random matrix based statistical mechanical procedure for ensemble-averaged calculations of optical properties of semiconductor NPs. This approach is based on deriving an effective fluctuating operator (EFO) for the NPs to account for the thermal fluctuations in the system. The method was applied to a series of CdSe quantum dots (Cd20Se20-Cd515Se515) and was used for calculation of ensemble-averaged excitonic properties including quasiparticle gap, optical gap, exciton binding energies, and electron-hole recombination probabilities. Statistical analysis of the results reveals that some excitonic properties are more sensitive to structural deformation than others. The EFO method was also used to study the effect of temperature and solvents on the NP properties, and a discussion of these results will be presented. The results from these calculations highlight the importance of ensemble averaging and demonstrate the limitations of using a single optimized NP structure for computational prediction of optical properties of NPs.

When a single structure is not sufficient: Effect of thermal deformation on excitonic properties of semiconductor nanoparticles

253rd National Meeting (2017)

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