This work presents a computational investigation of the impact of semiconductor type and quantum confinement on the inverse photoemission spectra of nanoparticles. Inverse photoemission occurs when an incident electron is captured by a material in one of the high energy unoccupied states which then subsequently de-excites to the LUMO state by emitting a photon. Using the kinetic energy of the captured electron and the energy of the generated photon, one can back-calculate the information about the unoccupied states. Inverse photoemission allows for direct spectroscopic investigation of the conduction band and is used in surface characterization of solids. In this work we have used many-body perturbation theory (MBPT) to calculate electron affinities, electron-capture cross-sections, inverse photoemission energies, and inverse photoemission oscillator strengths for a series of PbS, PbSe, CdS, and CdSe quantum dots. The results from this study show that the quantities related to the electron capture process and the photoemission process follow different scaling laws with respect to increasing dot size. The dependency electronic affinity energies versus dot size were found to be strongly impacted by electron-electron correlation interactions. Analysis of the electron-capture cross-sections showed that low-energy electrons with energies with energies less than or equal to 5 eV are suitable for studying unoccupied levels photoemission process possess appropriate overlap with the density of states. The results from this study open doors for using inverse photoemission as a spectroscopic technique for studying unoccupied energy levels and the density of states of the conduction band in nanomaterials and highlights the need for new controllable low-energy electron sources.

Inverse photoemision energies and oscillator strengths in PbS, PbSe, CdSe, and CdS quantum dots

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.