To improve optical properties, typical passivating ligands such as trimethyl-phosphine oxide, phosphine oxide, and hydrazine are used to cap PbSe quantum dots (QDs). Using Density Functional Theory (DFT) and Time Dependent DFT (TDDFT), we calculated the geometric and electronic structure of PbSe QDs partially and completely passivated by these ligands.   We found that all ligands interact very strongly with the QD surface with the largest binding of phosphine-oxide ligands. Ligand-ligand interactions were observed and QD-ligand binding energy was lowered. For passivated QDs, ligand orbitals (MOs) appeared deep within the valence and conduction bands. Most of the ligand-associated orbitals demonstrated a hybridized character and were spread over the QD and ligand atoms. Surface reconstruction of the bare and partially passivated QD resulted in semi-dark strongly red-shifted transitions (with low oscillator strength), whereas the full passivation led to much brighter and blue-shifted transitions in the absorption spectra of QDs.

Effect of capping ligands on optical properties of PbSe quantum dots

245th National Meeting (2013)

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