In Situ Spectroelectrochemical Determination of Energy Levels and Energy Level Offsets in Quantum-Dot Heterojunctions

Simon C. Boehme, Daniël Vanmaekelbergh, Wiel H. Evers, Laurens D A Siebbeles, Arjan J. Houtepen

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ. Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ.
Original languageEnglish
Pages (from-to)5164-5173
Number of pages10
JournalJournal of Physical Chemistry C
Volume120
Issue number9
DOIs
Publication statusPublished - 17 Mar 2016

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heterojunctions
energy levels
quantum dots
surface defects
charge transfer
trends
defects

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Boehme, Simon C. ; Vanmaekelbergh, Daniël ; Evers, Wiel H. ; Siebbeles, Laurens D A ; Houtepen, Arjan J. / In Situ Spectroelectrochemical Determination of Energy Levels and Energy Level Offsets in Quantum-Dot Heterojunctions. In: Journal of Physical Chemistry C. 2016 ; Vol. 120, No. 9. pp. 5164-5173.
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abstract = "Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ. Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ.",
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In Situ Spectroelectrochemical Determination of Energy Levels and Energy Level Offsets in Quantum-Dot Heterojunctions. / Boehme, Simon C.; Vanmaekelbergh, Daniël; Evers, Wiel H.; Siebbeles, Laurens D A; Houtepen, Arjan J.

In: Journal of Physical Chemistry C, Vol. 120, No. 9, 17.03.2016, p. 5164-5173.

Research output: Contribution to JournalArticleAcademicpeer-review

TY - JOUR

T1 - In Situ Spectroelectrochemical Determination of Energy Levels and Energy Level Offsets in Quantum-Dot Heterojunctions

AU - Boehme, Simon C.

AU - Vanmaekelbergh, Daniël

AU - Evers, Wiel H.

AU - Siebbeles, Laurens D A

AU - Houtepen, Arjan J.

PY - 2016/3/17

Y1 - 2016/3/17

N2 - Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ. Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ.

AB - Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ. Charge transfer in semiconductor heterojunctions is largely governed by the offset in the energy levels of the constituent materials. Unfortunately, literature values for such energy level offsets vary widely and are usually based on energy levels of the individual materials rather than of actual heterojunctions. Here we present a new method to determine absolute energy levels and energy level offsets in situ for films containing CdSe and PbSe quantum dots. Using spectroelectrochemistry, we find a type I offset at the CdSe-PbSe heterojunction. Whereas the energy level offset follows the expected size-dependent trend, the absolute positions of the 1Se level in the individual CdSe or PbSe quantum dots does not. This level varies by more than 0.5 eV, depending on film composition and surface defect concentration. Rather than extrapolating energy level offsets from measurements on pure CdSe or PbSe quantum-dot films, we suggest measuring energy level offsets in heterojunctions in situ.

U2 - 10.1021/acs.jpcc.5b12016

DO - 10.1021/acs.jpcc.5b12016

M3 - Article

VL - 120

SP - 5164

EP - 5173

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7455

IS - 9

ER -