English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report on systematic numerical study of carrier multiplication (CM)processes in spherically symmetric nanocrystal (NC) and bulk forms of PbSe andPbS representing the test bed for understanding basic aspects of CM dynamics.The adopted numerical method integrates our previously developed InterbandExciton Scattering Model (IESM) and the effective mass based electronicstructure model for the lead chalocogenide semiconductors. The analysis of theIESM predicted CM pathways shows complete lack of the pathway interferenceduring the biexciton photogeneration. This allows us to interpret the biexcitonphotogeneration as a single impact ionization (II) event and to explain majorcontribution of the multiple II events during the phonon-induced populationrelaxation into the total quantum efficiency (QE). We investigate the role ofquantum confinement on QE, and find that the reduction in the biexciton densityof states (DOS) overruns weak enhancement of the Coulomb interactions leadingto lower QE values in NCs as compared to the bulk on the absolute photon energyscale. However, represented on the photon energy scale normalized bycorresponding band gap energies the trend in QE is opposite demonstrating theadvantage of NCs for photovoltaic applications. Comparison to experiment allowsus to interpret the observed features and to validate the applicability rangeof our model. Modeling of QE as a function of pulse duration shows weakdependence for the gaussian pulses. Finally, comparison of the key quantitiesdetermining QE in PbSe and PbS demonstrates the enhancement of II rate in thelatter materials. However, the fast phonon-induced carrier relaxation processesin PbS can lead to the experimentally observed reduction in QE in NCs ascompared to PbSe NCs.

Numerical analysis of carrier multiplication mechanisms in nanocrystal and bulk forms of PbSe and PbS