Limits...
Electron relaxation in the CdSe quantum dot - ZnO composite: prospects for photovoltaic applications

View Article: PubMed Central - PubMed

ABSTRACT

Quantum dot (QD)-metal oxide composite forms a “heart” of the QD-sensitized solar cells. It maintains light absorption and electron-hole separation in the system and has been therefore extensively studied. The interest is largely driven by a vision of harvesting the hot carrier energy before it is lost via relaxation. Despite of importance of the process, very little is known about the carrier relaxation in the QD-metal oxide composites. In order to fill this gap of knowledge we carry out a systematic study of initial electron dynamics in different CdSe QD systems. Our data reveal that QD attachment to ZnO induces a speeding-up of transient absorption onset. Detailed analysis of the onset proves that the changes are caused by an additional relaxation channel dependent on the identity of the QD-ZnO linker molecule. The faster relaxation represents an important factor for hot carrier energy harvesting, whose efficiency can be influenced by almost 50%.

No MeSH data available.


Absorption characterization of the studied samples.Left: Scaled absorption spectra of bare QDs, QD-ZnO (2.5x) and QD-SiO2 (14.2x). Spectrum of QD-ZnO was corrected for scattering contribution. Right: Absorption edge of ZnO in the QD-ZnO sample (upper right panel); scattering contribution and the original QD-ZnO spectrum (lower right panel).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5384232&req=5

f1: Absorption characterization of the studied samples.Left: Scaled absorption spectra of bare QDs, QD-ZnO (2.5x) and QD-SiO2 (14.2x). Spectrum of QD-ZnO was corrected for scattering contribution. Right: Absorption edge of ZnO in the QD-ZnO sample (upper right panel); scattering contribution and the original QD-ZnO spectrum (lower right panel).

Mentions: The three studied samples are schematically depicted in the insets of Figure 1. QDs dispersed in ethanol (black color) are the simplest system, as they consist of individual non-interacting QDs. Pronounced excitonic features, which can be clearly resolved, imply a narrow distribution of QD sizes in the sample. From position of the lowest excitonic peak 2.12 eV (586 nm) we can estimate the QD size to about 4 nm18.


Electron relaxation in the CdSe quantum dot - ZnO composite: prospects for photovoltaic applications
Absorption characterization of the studied samples.Left: Scaled absorption spectra of bare QDs, QD-ZnO (2.5x) and QD-SiO2 (14.2x). Spectrum of QD-ZnO was corrected for scattering contribution. Right: Absorption edge of ZnO in the QD-ZnO sample (upper right panel); scattering contribution and the original QD-ZnO spectrum (lower right panel).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384232&req=5

f1: Absorption characterization of the studied samples.Left: Scaled absorption spectra of bare QDs, QD-ZnO (2.5x) and QD-SiO2 (14.2x). Spectrum of QD-ZnO was corrected for scattering contribution. Right: Absorption edge of ZnO in the QD-ZnO sample (upper right panel); scattering contribution and the original QD-ZnO spectrum (lower right panel).
Mentions: The three studied samples are schematically depicted in the insets of Figure 1. QDs dispersed in ethanol (black color) are the simplest system, as they consist of individual non-interacting QDs. Pronounced excitonic features, which can be clearly resolved, imply a narrow distribution of QD sizes in the sample. From position of the lowest excitonic peak 2.12 eV (586 nm) we can estimate the QD size to about 4 nm18.

View Article: PubMed Central - PubMed

ABSTRACT

Quantum dot (QD)-metal oxide composite forms a “heart” of the QD-sensitized solar cells. It maintains light absorption and electron-hole separation in the system and has been therefore extensively studied. The interest is largely driven by a vision of harvesting the hot carrier energy before it is lost via relaxation. Despite of importance of the process, very little is known about the carrier relaxation in the QD-metal oxide composites. In order to fill this gap of knowledge we carry out a systematic study of initial electron dynamics in different CdSe QD systems. Our data reveal that QD attachment to ZnO induces a speeding-up of transient absorption onset. Detailed analysis of the onset proves that the changes are caused by an additional relaxation channel dependent on the identity of the QD-ZnO linker molecule. The faster relaxation represents an important factor for hot carrier energy harvesting, whose efficiency can be influenced by almost 50%.

No MeSH data available.