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
Study of quantum dots on solar energy applications
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. (Nanoparticles for 3rd generation solar cells)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis studies p-i-n GaAs solar cells with self-assembled InAs quantum dots (QDs) inserted. The values of this work lie in three aspects. First, by comparing the cell performance with QDs in the i-region and the n-region, the photocurrent (PC) production from QDs by thermal activation and/or intermediate band (IB) absorption is proved to be much lower in efficiency than tunneling. Second, the efficiency of PC production from QDs, characterized by PC spectrum, is helpful to design QD-based photodetectors. Third, closely spaced InAs QD layers allow a strong inter-layer tunneling, leading to an effective PC production from QD deep states, potential for solar cell application. Fourth, from the temperature-dependent PC spectra the minority photohole thermal escape is found to be dominant on PC production from QDs in the n-region. The thermal activation energy reflects the potential variations formed by electron filling in QDs.

Apart from InAs QDs, this thesis also explores the blinking correlation between two colloidal CdSe QDs. For QD distance of 1 µm or less, there is a bunched correlation at delay τ = 0, meaning that the two QDs blink synchronously. Such correlation disappears gradually as QD distance increases. The correlation is possibly caused by the stimulated emission between the two nearby QDs.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xii, 60 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2012:12
Keyword [en]
Epitaxial InAs quantum dot solar cell
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:kth:diva-94021ISBN: 978-91-7501-352-7 (print)OAI: oai:DiVA.org:kth-94021DiVA: diva2:525075
Public defence
2012-06-04, FA32, AlbaNova Universitetscentrum, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20120507Available from: 2012-05-07 Created: 2012-05-04 Last updated: 2012-05-07Bibliographically approved
List of papers
1. Effect of built-in electric field in photovoltaic InAs quantum dot embedded GaAs solar cell
Open this publication in new window or tab >>Effect of built-in electric field in photovoltaic InAs quantum dot embedded GaAs solar cell
Show others...
2011 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 103, no 2, 335-341 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, three p-i-n GaAs solar cells were grown and characterized, one with InAs quantum dot (QD) layers embedded in the depletion region (sample A), one with QD layers embedded in the n (-) base region (B), and the third without QDs (control sample C). QD-embedded solar cells (samples A and B) show broad photoluminescence spectra due to QD multi-level emissions but have lower open-circuit voltages V (oc) and lower photovoltaic (PV) efficiencies than sample C. On the other hand, the short-circuit current density J (sc) in sample A is increased while it is decreased in sample B. Theoretical analysis shows that in sample B where the built-in electric field in QDs is zero, electrons tend to occupy QDs and strong potential variations exist around QDs which deteriorate the electron mobility in the n (-) base region so that J (sc) in sample B is decreased. Hole trapping and electron-hole recombination in QDs are also enhanced in sample B, resulting in a reduced V (oc) and thus a worse PV effect. In sample A, a strong built-in field exists in QD layers, which facilitates photo-carrier extraction from QDs and thus J (sc) is increased. However, QDs in the depletion region in sample A act also as recombination-generation centers so that the dark saturated current density is drastically increased, which reduces V (oc) and the total PV effect. In conclusion, a nonzero built-in electric field around QDs is vital for using QDs to increase the PV effect in conventional p-i-n GaAs solar cells.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-33251 (URN)10.1007/s00339-010-6152-8 (DOI)000289558900013 ()2-s2.0-79955852769 (Scopus ID)
Note
QC 20110504Available from: 2011-05-04 Created: 2011-05-02 Last updated: 2017-12-11Bibliographically approved
2. Quantum-dot-induced optical transition enhancement in InAs quantum-dot-embedded p-i-n GaAs solar cells
Open this publication in new window or tab >>Quantum-dot-induced optical transition enhancement in InAs quantum-dot-embedded p-i-n GaAs solar cells
Show others...
2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 11, 113514- p.Article in journal (Refereed) Published
Abstract [en]

Photocurrents (PCs) of three p-i-n GaAs solar cells, sample A with InAs quantum dots (QDs) embedded in the depletion region, B with QDs in the n region, and C without QDs, were studied experimentally and theoretically. Above GaAs bandgap, the PC of A is increased, while B is decreased with respect to C, since in A, the QD-induced reflection of hole wave function increases its overlap with electron wave function so that the optical transition rate is enhanced, while carrier mobility in B is reduced due to QD-induced potential variations. Moreover, A and B have increased PCs in the sub-GaAs-bandgap range due to QD optical absorptions.

Keyword
Well Infrared Photodetector, Photocurrent, Efficiency
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-42371 (URN)10.1063/1.3638488 (DOI)000295034400089 ()2-s2.0-80053190661 (Scopus ID)
Note
QC 20111010Available from: 2011-10-10 Created: 2011-10-10 Last updated: 2017-12-08Bibliographically approved
3. Photocarrier extraction from closely stacked InAs quantum dot layers em-bedded in GaAs solar cells
Open this publication in new window or tab >>Photocarrier extraction from closely stacked InAs quantum dot layers em-bedded in GaAs solar cells
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-94083 (URN)
Note
QS 2012Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2012-05-07Bibliographically approved
4. Observation of bunched blinkings from individual colloidal CdSe/CdS andCdSe/ZnS quantum dots
Open this publication in new window or tab >>Observation of bunched blinkings from individual colloidal CdSe/CdS andCdSe/ZnS quantum dots
Show others...
(English)Article in journal (Other academic) Submitted
National Category
Biological Sciences
Identifiers
urn:nbn:se:kth:diva-94089 (URN)
Note
QS 2012Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2012-05-07Bibliographically approved

Open Access in DiVA

XiangjunShang_thesis(3986 kB)3120 downloads
File information
File name FULLTEXT01.pdfFile size 3986 kBChecksum SHA-512
7a60a531605d36464b3037a77b0650cee3b1c76ad66d7558d33fb3d9209fe9668e1981626ea03150673b0159048bf1158c12a3161551137672da23d706b58ccc
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Shang, Xiangjun
By organisation
Theoretical Chemistry and Biology
Nano Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 3120 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 477 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