Charge Transfer Dynamics in Cadmium Chalcogenide Quantum Dots based Heterostructures

Quantum confinement effects in semiconductor nanocrystals or quantum dots (QDs) give rise to unusual electronic properties such as, size dependent bandgaps, high molar absorptivities and in some cases, hot carrier extraction and multi-exciton generation, which makes them suitable to harvest solar energy. Competition between charge transfer and electron-hole recombination determines the efficiency of charge separation and thus the performance of QDs based electronic devices. Compared to the bulk semiconductors, surface of QDs significantly affects the optoelectronic properties of QDs due to high surface to volume ratios. The difference in the chemical environment of the surface atoms with that of bulk results in mid-gap states which can trap photoexcited charge carriers. This dissertation explores the role of these surface states in charge transfer and draws comparisons with charge transfer from band edge states. Mesoporous titanium oxide (TiO2) is often used as the electron extracting component in dyesensitized and QDs based solar cells. CdSe QDs were assembled on TiO2 nanoparticles (NPs) using linker assisted assembly (LAA) approach and electron transfer was studied from band edge and surface states of CdSe QDs to TiO2 NPs using steady-state and time-resolved spectroscopy. Electron transfer was found to be 2-3 times faster from band edge states as compared to surface states, consistent with driving force dependent electron transfer. Well passivated core/shell CdSe/ZnS QDs showed improved electron transfer performance to TiO2 despite the presence of a spatial and energetic barrier of ZnS shell.

Grantor dc:publisher

State University of New York at Buffalo

Year dc:date.issued

2018

Author dc:creator

• Chauhan, Saurabh

Contributors dc:contributor

• Watson, David
• Chemistry

• chemistry
• materials science
• alternative energy

Statement dc:rights

• Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.
• Copyright retained by author.

Language dc:language

eng

Handle dc:identifier

http://hdl.handle.net/10477/78076

OAI record oai:identifier

https://ubir.buffalo.edu/oai/request?verb=GetRecord&metadataPrefix=qdc&identifier=oai%3Aubir.buffalo.edu%3A10477%2F78076