Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Solar cells sensitized with type-II ZnSe-CdS core/shell colloidal quantum dots
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
KTH, School of Biotechnology (BIO).ORCID iD: 0000-0002-2442-1809
Show others and affiliations
2011 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 5, 1536-1538 p.Article in journal (Refereed) Published
Abstract [en]

Type-II quantum dots (QDs) were applied for QDs-sensitized solar cells for the first time and showed prominent absorbed photon to current conversion efficiency.

Place, publisher, year, edition, pages
2011. Vol. 47, no 5, 1536-1538 p.
Keyword [en]
SELF-ASSEMBLED LAYERS, SEMICONDUCTOR NANOCRYSTALS, TIO2 NANOSTRUCTURES, ELECTRON INJECTION, SHAPE CONTROL
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-30262DOI: 10.1039/c0cc03401kISI: 000286389500042Scopus ID: 2-s2.0-78751549134OAI: oai:DiVA.org:kth-30262DiVA: diva2:399378
Funder
Swedish e‐Science Research Center
Note

QC 20110222

Available from: 2011-02-22 Created: 2011-02-21 Last updated: 2016-12-21Bibliographically approved
In thesis
1. Rational design of nanoparticles for biomedical imaging and photovoltaic applications
Open this publication in new window or tab >>Rational design of nanoparticles for biomedical imaging and photovoltaic applications
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis aims to rationally design nanoparticles and promote their applications in biomedical imaging and photovoltaic cells.

Quantum dots (QDs) are promising fluorescent probes for biomedical imaging. We have fabricated two types of MSA capped QDs: CdTe/ZnSe core/shell QDs synthesized via an aqueous method and CdTe QDs via a hydrothermal method. They present high quantum yields (QYs), narrow emission band widths, high photo- and pH-stability, and low cytotoxicity. QD-IgG probes were produced and applied for labeling breast cancer marker HER2 proteins on MCF-7 cells.

For the purpose of single molecule tracking using QDs as fluorescent probes, we use small affibodies instead of antibodies to produce QD-affibody probes. Smaller QD-target protein complexes are obtained using a direct immunofluorescence approach. These QD-affibody probes are developed to study the dynamic motion of single HER2 proteins on A431 cell membranes.

Fluorescence blinking in single QDs is harmful for dynamic tracking due to information loss. We have experimentally studied the blinking phenomenon and the mechanism behind. We have discovered an emission bunching effect that two nearby QDs tend to emit light synchronously. The long-range Coulomb potential induced by the negative charge on the QD surface is found to be the major cause for the single QD blinking and the emission bunching in QD pairs.

We have studied the in vitro cytotoxicity of CdTe QDs to human umbilical vein endothelial cells (HUVECs). The QDs treatment increases the intracellular reactive oxygen species (ROS) level and disrupts the mitochondrial membrane potential. The protein expression levels indicate that the mitochondria apoptosis is the main cause of HUVCEs apoptosis induced by CdTe QDs.

Gold nanorods (GNRs) are scattering probes due to their tunable surface plasmon resonance (SPR) enhanced scattering spectrum. In order to control the yield and morphology of GNRs, we have systematically studied the effects of composition and concentration in the growth solution on the quality of the GNRs produced via a seed-mediated method. The aspect ratios of GNRs were found to be linearly depended on the concentration ratio of silver ions and CTAB. The high quality GNRs obtained were adsorbed to COS-7 cell membranes for dark field imaging.

We have rationally designed two types of QDs by wave function engineering so as to improve the efficiency of QD-sensitized solar cells. A reversed type-I CdS/CdSe QD confines excitons in the shell region, whereas a type-II ZnSe/CdS QD separates electrons in the shell and holes in the core. Their absorbed photon-to-current efficiencies (APCE) are as high as 40% and 60% respectively.

In conclusion, rationally designed nanoparticles are proven a high potential for applications as probes in biomedical labeling, imaging and molecule tracking, and as sensitizers for photovoltaic cells.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-33346 (URN)978-91-7415-973-8 (ISBN)
Public defence
2011-05-24, FB52, AlbaNova, Roslagstullsbacken, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20110511Available from: 2011-05-11 Created: 2011-05-03 Last updated: 2011-05-11Bibliographically approved
2. The Study of II-VI Semiconductor Nanocrystals Sensitized Solar Cells
Open this publication in new window or tab >>The Study of II-VI Semiconductor Nanocrystals Sensitized Solar Cells
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductor nanocrystals, also referred to as quantum dots (QDs), have been the focus of great scientific and technological efforts in solar cells, as a result of their advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties. Due to the multi-electron generation effect, the theoretically maximum efficiency of quantum dots-sensitized solar cells (QDSCs) is as high as 44%, which is much higher than that of dye-sensitized solar cells (DSCs). Thus QDSCs have a clear potential to overtake the efficiency of all other kinds of solar cells.

In recent years, the efficiency of QDSCs has been improved very quickly to around 5%. It is however still much lower than that of DSCs. The low efficiency is mostly caused by the high electron loss between electrolyte and electrodes and the lack of an efficient electrolyte. In this thesis, we have been working to enhance the performance of QDSCs with II-VI group nanocrystals by increasing the electron injection efficiency from QDs to TiO2 and developing new redox couples in electrolyte.

To increase the electron injection, firstly, colloidal ZnSe/CdS type-II QDs were synthesized and applied for QDSCs for the first time, whose photoelectron and photohole are located on CdS shell and ZnSe core, respectively. The spatial separation between photoelectron and photohole can effectively enhance the charge extraction efficiency, facilitating electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to the high photon to current conversion efficiency. Furthermore, a comparison between the performances of ZnSe/CdS and CdS/ZnSe QDs shows that the electron distribution is important for the electron injection of the QDs in QDSCs. Secondly, colloidal CdS/CdSe quantum rods (QRs) were applied to a quantum rod-sensitized solar cell (QRSCs) that showed a higher electron injection efficiency than analogous QDSCs. It is concluded that reducing the carrier confinement dimensions of nanocrystals can improve electron injection efficiency of nanocrystal sensitized solar cells.

In this thesis, two types of organic electrolytes based McMT-/BMT and TMTU/TMTU-TFO were used for QDSCs. By reducing the charge recombination between the electrolyte and counter electrode, fill factor (FF) of these QDSCs was significantly improved. At the same time, the photovoltages of the QDSCs were remarkably increased. As a result, the overall conversion efficiency of QDSCs based on the new electrolytes was much higher than that with a commonly used inorganic electrolyte.

In addition, CdS QDSCs on NiO photoelectrode were studied which shows a n-type photovoltaic performance. This performance is attributed to the formation of a thin Cd metal film before CdS QDs formation on NiO. Since the CB edge of CdS sits between the Fermi level and the CB edge of Cd metal, a much strong electron transfer between Cd and CdS QD is obtained, resulting in the observed n-type photovoltaic performance of these CdS/NiO QDSCs.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 41 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2012:5
Keyword
quantum dots, quantum rods, nanocrytals, solar cells, colloidal, type-II, electron injection, organic electrolyte.
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-93752 (URN)
Presentation
2012-04-27, RB15, AlbaNova Universitetscentrum, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120425Available from: 2012-04-25 Created: 2012-04-25 Last updated: 2012-04-25Bibliographically approved
3. Development of Nanoparticle Sensitized Solar Cells
Open this publication in new window or tab >>Development of Nanoparticle Sensitized Solar Cells
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, I have been working with the development of nanoparticle sensitized solar cells. In the subarea of quantum dot sensitized solar cells (QDSCs), I have investigated type-II quantum dots (QDs), quantum rods (QRs) and alloy QDs, and developed novel redox couples as electrolytes. I have also proposed upconversion nanoparticles as energy relay materials for dye-sensitized solar cells (DSCs).

Colloidal ZnSe/CdS type-II QDs were applied for QDSCs for the first time. The interesting features of those refer to that their photoelectrons and photoholes are located on the different parts of the dot, namely in the CdS shell and in the ZnSe core, respectively. That spatial separation between photoelectrons and photoholes can so effectively enhance the charge extraction efficiency, thus facilitating the electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to a high photon to current conversion efficiency. Furthermore, a comparison between the photovoltaic performance of ZnSe/CdS and CdS/ZnSe QDSCs shows that the electron distribution is important for the electron injection of the QDs.

Colloidal CdS/CdSe QRs were applied to quantum rod-sensitized solar cells (QRSCs). They showed a higher electron injection efficiency than the analogous QDSCs. It is concluded that reduction of the carrier confinement dimensions of the nanoparticles can improve the electron injection efficiency of the nanoparticle sensitized solar cells.

Two types of organic electrolytes based on the redox couples of McMT-/BMT (OS1) and TMTU/TMTU-TFO (OS2) were used for the QDSCs. By reducing the charge recombination between the electrolyte and the counter electrode, the fill factor and the photovoltage of these QDSCs were significantly improved, resulting in a higher efficiency for the studied solar cells than that with a commonly used inorganic electrolyte.

Ternary-alloy PbxCd1-xS QDs used as photosensitizers for QDSCs were found to improve the photocurrent compared to the corresponding CdS and PbS QDs. By considering the effect of different ratios of Pb to Cd in thePbxCd1-xS QDs on the photovoltaic performance it was discovered that the photocurrent increases and the photovoltage decreases with the increase of the ratio in a certain range.

Upconversion (UC) nanoparticles provide a strategy to develop panchromatic solar cells. Three types of UC nanoparticles employed by DSCs were confirmed to work as energy relay materials for effectively extending the light-harvesting spectrum to the near-infrared (NIR) region. They were also found to play a role as scattering centers to enhance the photovoltaic performance of the solar cells.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 70 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2013:16
Keyword
quantum dots, quantum rods, nanoparticles, solar cells, colloidal, type-II, electron extraction, alloy, organic electrolyte, energy relay, upconversion.
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-129382 (URN)978-91-7501-862-1 (ISBN)
Public defence
2013-10-24, FB42, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20131002

Available from: 2013-10-02 Created: 2013-09-28 Last updated: 2013-10-02Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Fu, YingSun, LichengÅgren, Hans

Search in DiVA

By author/editor
Ning, ZhijunTian, HainingYuan, ChunzeFu, YingQin, HaiyanSun, LichengÅgren, Hans
By organisation
Theoretical Chemistry (closed 20110512)Organic ChemistrySchool of Biotechnology (BIO)
In the same journal
Chemical Communications
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 193 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf