3 years ago

Highly Stable Colloidal “Giant” Quantum Dots Sensitized Solar Cells

Highly Stable Colloidal “Giant” Quantum Dots Sensitized Solar Cells
François Vidal, Xin Tong, Haiguang Zhao, Federico Rosei, Daniele Benetti, David Barba, Yufeng Zhou, Fabiola Navarro-Pardo, Zhiming M. Wang, Gurpreet S. Selopal
Colloidal quantum dots (QDs) are widely studied due to their promising optoelectronic properties. This study explores the application of specially designed and synthesized “giant” core/shell CdSe/(CdS)x QDs with variable CdS shell thickness, while keeping the core size at 1.65 nm, as a highly efficient and stable light harvester for QD sensitized solar cells (QDSCs). The comparative study demonstrates that the photovoltaic performance of QDSCs can be significantly enhanced by optimizing the CdS shell thickness. The highest photoconversion efficiency (PCE) of 3.01% is obtained at optimum CdS shell thickness ≈1.96 nm. To further improve the PCE and fully highlight the effect of core/shell QDs interface engineering, a CdSexS1−x interfacial alloyed layer is introduced between CdSe core and CdS shell. The resulting alloyed CdSe/(CdSexS1−x)5/(CdS)1 core/shell QD-based QDSCs yield a maximum PCE of 6.86%, thanks to favorable stepwise electronic band alignment and improved electron transfer rate with the incorporation of CdSexS1−x interfacial layer with respect to CdSe/(CdS)6 core/shell. In addition, QDSCs based on “giant” core/CdS-shell or alloyed core/shell QDs exhibit excellent long-term stability with respect to bare CdSe-based QDSCs. The giant core/shell QDs interface engineering methodology offers a new path to improve PCE and the long-term stability of liquid junction QDSCs. The “giant” alloyed CdSe/(CdSexS1−x)5/(CdS)1 core/shell quantum dots (QDs) show superior optoelectronic properties, such as broader absorption spectrum, and better carrier separation and transfer rate with respect to CdSe/(CdS)6 core/shell QDs. The alloyed core/shell QDs sensitized solar cells (QDSCs) exhibit a photoconversion efficiency of 6.86% and excellent long-term stability, and offer a new path for liquid junction QDSCs technology.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adfm.201701468

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