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Use of Quantum Dots for Intermediate Band Solar Cells. Peter Matheu EE 235 – “Nanoscale Fabrication” Professor Connie Chang-Hasnain. March 17, 2008. Outline. Introduction to quantum dots (QDs) as absorbers MEG, minibands, high Voc Motivation behind QW or QD absorbers for solar cells

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Peter matheu ee 235 nanoscale fabrication professor connie chang hasnain

Use of Quantum Dots for Intermediate Band Solar Cells

Peter Matheu

EE 235 – “Nanoscale Fabrication”

Professor Connie Chang-Hasnain

March 17, 2008


Outline
Outline

  • Introduction to quantum dots (QDs) as absorbers

    • MEG, minibands, high Voc

  • Motivation behind QW or QD absorbers for solar cells

    • Theoretical limit

  • The intermediate band (IB)

  • Experimental results and verification

H.Henry, J. Appl. Phys., 51, 4494 (1980)

Peter Matheu


Quantum dots are hot and cool
Quantum Dots are Hot (and Cool)

Quantum dot absorbers exhibit confinement such that absorption of a photon of energy ≥ 2*Egap can lead to either

(a) Hot carriers increasing the Voc

or

(b) Multiple Exciton Generation (MEG)

A. Luque, A. Martie, and A. Nozik, MRS Bulletin, 32, 2007.

Peter Matheu


Meg verification
MEG Verification

Peter Matheu


Self assembly of qds
Self-Assembly of QDs

Periodic QDs in close proximity causes the formation of ‘mini-bands’ much like a superlattice of quantum wells.

A. Luque, A. Martie, and A. Nozik, MRS Bulletin, 32, 2007.

Peter Matheu


The intermediate band
The Intermediate Band

  • Restrict the intermediate band physically in the middle of a p-i-n style solar cell

    • Mitigates reduction in Voc

  • “2 photon” absorption (VB  IB, IB  CB) for intermediate process

  • Theoretical limit for IBSC approximately 47% - 63% (depending on concentration)

Peter Matheu


Schematic example
Schematic Example

MBE or epi-style thin film growth utilizing the S-K method for self assembly of quantum dots

Peter Matheu


Experimental results
Experimental Results

A. Luque, A. Martie, and A. Nozik, MRS Bulletin, 32, 2007.

Peter Matheu


Experimental results1
Experimental Results

A. Martí, et. al., PRL, 97, 247701, 2006.

Peter Matheu


Experimental results2
Experimental Results

R. B. Laghumavarapu, et. al., APL, 90, 173215, 2007.

Peter Matheu


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