Journal
ACS NANO
Volume 9, Issue 11, Pages 11286-11295Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.5b04917
Keywords
quantum dot-sensitized solar cells; copper-indium-selenide; ZnS overlayers; heavy metal-free; recombination control
Categories
Funding
- Global Frontier R&D Program on Center for Multiscale Energy System - National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea [2012M3A6A7054856]
- Technology Development Program to Solve Climate Changes - National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea [2015M1A2A2056824]
- KIST
- Research Center Program of Institute for Basic Science in Korea [IBS-R006-D1]
- National Research Foundation of Korea [2015M1A2A2056824, 2012M3A6A7054856] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Copper-indium-selenide (CISe) quantum dots (QDs) are a promising alternative to the toxic cadmium- and lead-chalcogenide QDs generally used in photovoltaics due to their low toxicity, narrow band gap, and high absorption coefficient. Here, we demonstrate that the photovoltaic performance of CISe QD-sensitized solar cells (QDSCs) can be greatly enhanced simply by optimizing the thickness of ZnS overlayers on the QD-sensitized TiO2 electrodes. By roughly doubling the thickness of the overlayers compared to the conventional one, conversion efficiency is enhanced by about 40%. Impedance studies reveal that the thick ZnS overlayers do not affect the energetic characteristics of the photoanode, yet enhance the kinetic characteristics, leading to more efficient photovoltaic performance. In particular, both interfacial electron recombination with the electrolyte and nonradiative recombination associated with QDs are significantly reduced. As a result, our best cell yields a conversion efficiency of 8.10% under standard solar illumination, a record high for heavy metal-free QD solar cells to date.
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