Revealing Trap States in Lead Sulphide Colloidal Quantum Dots by Photoinduced Absorption Spectroscopy

Kahmann S, Sytnyk M, Schrenker N, Matt G, Spiecker E, Heiß W, Brabec C, Loi MA (2017)


Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2017

Journal

Publisher: Blackwell Publishing Ltd

DOI: 10.1002/aelm.201700348

Abstract

Due to their large surface to volume ratio, colloidal quantum dots (CQDs)
are often considered to exhibit a significant amount of surface defects. Such
defects are one possible source for the formation of in-gap states (IGS), which
can enhance the recombination of excited carriers, i.e., work as electrical traps.
These traps are investigated for lead sulphide CQDs of different size, covered
with different ligands using a mid-infrared photoinduced absorption (PIA)
technique. The obtained PIA spectra reveal two distinct absorption bands,
whose position depends on the particle size, i.e., the electronic confinement
in the CQDs. Smaller particles exhibit deeper traps. The chemical nature of
the capping ligand does not affect the resulting position other than due to its
change in confinement, but better passivating species lead to smaller signals.
Furthermore, ligand specific narrow lines observed are superimposed on the
broad electronic background of the PIA spectra, which is attributed to Fano
resonances caused by the interplay of the narrow molecular vibrations and the
continuum of trap states. Mid-infrared photoinduced absorption represents a
valuable tool to unravel distributions of IGS in CQDs and allows for an assessment
of the quality of ligand exchanged films. These findings have implications
for understanding the performances of CQD-based (opto-) electronic
devices, such as solar cells, transistors, or quantum dot light emitting diodes,
which are limited by frequent carrier trapping events.

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How to cite

APA:

Kahmann, S., Sytnyk, M., Schrenker, N., Matt, G., Spiecker, E., Heiß, W.,... Loi, M.A. (2017). Revealing Trap States in Lead Sulphide Colloidal Quantum Dots by Photoinduced Absorption Spectroscopy. Advanced Electronic Materials. https://dx.doi.org/10.1002/aelm.201700348

MLA:

Kahmann, Simon, et al. "Revealing Trap States in Lead Sulphide Colloidal Quantum Dots by Photoinduced Absorption Spectroscopy." Advanced Electronic Materials (2017).

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