The nature of photoexcitations and carrier multiplication in low-dimensional semiconductors

Doctoral thesis (2019)

Authors

A. Kulkarni ChemE/Opto-electronic Materials - AS
Research Group
ChemE/Opto-electronic Materials (AS) (TU Delft)
Copyright: © 2019 A. Kulkarni
DOI: https://doi.org/10.4233/uuid:32a7a099-94c3-45f7-955b-b14628996011
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Published Date

2019

Language

English

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Faculty

Applied Sciences

Department

ChemE/Chemical Engineering

Research Group

ChemE/Opto-electronic Materials

Abstract

The aim of this thesis is to study the nature of photoexcitations and carrier multiplication in low-dimensional semiconductors using ultrafast spectroscopy techniques. Ongoing from a macroscopic scale to a nanoscale, the electronic and
optical properties of a material become size dependent, and differ significantly from their bulk counterpart due to quantum confinement, and the surrounding dielectric environment. Electrons and holes in nano-semiconductors can attract each other to form neutral bound electron-hole pairs known as excitons. Stable robust excitons are useful to achieve optical gain and lasing. The Coulomb interaction between electrons and holes in nano-semiconductors is enhanced due to quantum confinement, which can lead to the creation of multiple electron-hole pairs per single absorbed photon via a process called carrier multiplication (CM). CM is beneficial to achieve a power conversion efficiency in a solar cell beyond the Shockley-Quiesser limit.

Files

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