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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. 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

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  1. Use of Quantum Dots for Intermediate Band Solar Cells Peter Matheu EE 235 – “Nanoscale Fabrication” Professor Connie Chang-Hasnain March 17, 2008

  2. 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

  3. 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

  4. MEG Verification Peter Matheu

  5. 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

  6. 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

  7. Schematic Example MBE or epi-style thin film growth utilizing the S-K method for self assembly of quantum dots Peter Matheu

  8. Experimental Results A. Luque, A. Martie, and A. Nozik, MRS Bulletin, 32, 2007. Peter Matheu

  9. Experimental Results A. Martí, et. al., PRL, 97, 247701, 2006. Peter Matheu

  10. Experimental Results R. B. Laghumavarapu, et. al., APL, 90, 173215, 2007. Peter Matheu

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