Effects of Lead Halide Bridging of 2D Nanoplates on Excited State Relaxation Dynamics

PbSe Nanoplates (NPLs) – the 2-D nanostructures – are promising alternatives to quantum dots because it permits better controls on surface effects while holding all benefits of the electronic and optical properties resulted from the confinement. A Pb halide bridged self-assembled 2D PbSe NPL synthesized as reported by Koh et al¹, show efficient carrier multiplication, enhance conductivity, and stimulated emission with a narrow width. These properties make NPLs promising materials for solar cell and lighting technologies. However, an impact of the interplay between 1D-confinement and Pb halide-originated defects, as well as effects of different halide molecule on relaxation dynamics are still unclear. We apply DFT based non-adiabatic dynamics combined with a simplified trajectory surface hopping (TSH) method to produce relaxation dynamics of charge carriers in Pb-halide bridged PbSe NPL. The electronic structure calculation shows that almost symmetric valance and conduction bands, while PbCl₂ contributes to deeper valance band states, which could have effects on relaxation mechanisms of the hot carriers. Our calculation predicts about a twice faster relaxation of hot holes (< 1 ps), compared to the hot electron.

(1) Koh, W. et al. J. Am. Chem. Soc. 2017 DOI: 10.1021/jacs.6b11945.