Enhanced Electron Lifetime of CdSe/CdS Quantum Dot (QD) Sensitized Solar Cells Using ZnSe Core-Shell Structure with Efficient Regeneration of Quantum Dots

Rasin Ahmed; Long Zhao; Attila J. Mozer; Geoffrey Will; John Bell; Hongxia Wang

doi:10.1021/jp510339z

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Enhanced Electron Lifetime of CdSe/CdS Quantum Dot (QD) Sensitized Solar Cells Using ZnSe Core-Shell Structure with Efficient Regeneration of Quantum Dots

Journal article

Peer reviewed

Enhanced Electron Lifetime of CdSe/CdS Quantum Dot (QD) Sensitized Solar Cells Using ZnSe Core-Shell Structure with Efficient Regeneration of Quantum Dots

Rasin Ahmed, Long Zhao, Attila J. Mozer, Geoffrey Will, John Bell and Hongxia Wang

The Journal of Physical Chemistry Part C, Vol.119(5), pp.2297-2307

2015

DOI: https://doi.org/10.1021/jp510339z

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Abstract

coating materials

layers

oxides

quantum dots

solar cells

Research on development of efficient passivation materials for high performance and stable quantum dot sensitized solar cells (QDSCs) is highly important. While ZnS is one of the most widely used passivation material in QDSCs, an alternative material based on ZnSe which was deposited on CdS/CdSe/TiO2 photoanode to form a semi-core/shell structure has been found to be more efficient in terms of reducing electron recombination in QDSCs in this work. It has been found that the solar cell efficiency was improved from 1.86% for ZnSe0 (without coating) to 3.99% using 2 layers of ZnSe coating (ZnSe2) deposited by successive ionic layer adsorption and reaction (SILAR) method. The short circuit current density (J(sc)) increased nearly 1-fold (from 7.25 mA/cm(2) to13.4 mA/cm(2)), and the open circuit voltage (V-oc) was enhanced by 100 mV using ZnSe2 passivation layer compared to ZnSe0. Studies on the light harvesting efficiency (eta(LHE)) and the absorbed photon-to-current conversion efficiency (APCE) have revealed that the ZnSe coating layer caused the enhanced eta(LHE) at wavelength beyond 500 nm and a significant increase of the APCE over the spectrum 400550 nm. A nearly 100% APCE was obtained with ZnSe2, indicating the excellent charge injection and collection process in the device. The investigation on charge transport and recombination of the device has indicated that the enhanced electron collection efficiency and reduced electron recombination should be responsible for the improved J(sc) and V-oc of the QDSCs. The effective electron lifetime of the device with ZnSe2 was nearly 6 times higher than ZnSe0 while the electron diffusion coefficient was largely unaffected by the coating. Study on the regeneration of QDs after photoinduced excitation has indicated that the hole transport from QDs to the reduced species (S2-) in electrolyte was very efficient even when the QDs were coated with a thick ZnSe shell (three layers). For comparison, ZnS coated CdS/CdSe sensitized solar cell with optimum shell thickness was also fabricated, which generated a lower energy conversion efficiency (eta = 3.43%) than the ZnSe based QDSC counterpart due to a lower V-oc and FF. This study suggests that ZnSe may be a more efficient passivation layer than ZnS, which is attributed to the type II energy band alignment of the core (CdS/CdSe quantum dots) and passivation shell (ZnSe) structure, leading to more efficient electron-hole separation and slower electron recombination.

Details

Title: Enhanced Electron Lifetime of CdSe/CdS Quantum Dot (QD) Sensitized Solar Cells Using ZnSe Core-Shell Structure with Efficient Regeneration of Quantum Dots
Authors: Rasin Ahmed (Author) - Queensland University of Technology
Long Zhao (Author) - ARC Centre of Excellence for Electromaterials Science
Attila J. Mozer (Author) - ARC Centre of Excellence for Electromaterials Science
Geoffrey Will (Author) - Queensland University of Technology
John Bell (Author) - Queensland University of Technology
Hongxia Wang (Corresponding Author) - Queensland University of Technology
Publication details: The Journal of Physical Chemistry Part C, Vol.119(5), pp.2297-2307
Publisher: American Chemical Society
DOI: 10.1021/jp510339z
ISSN: 1932-7455
Grant note: Queensland University of Technology FT120100674 / Australian Research Council (ARC)
Organisation Unit: School of Science, Technology and Engineering
Language: English
Record Identifier: 99737873802621
Output Type: Journal article

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Collaboration types: Domestic collaboration
Web Of Science research areas: Chemistry, Physical; Materials Science, Multidisciplinary; Nanoscience & Nanotechnology

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