Lead Telluride Quantum Dot Solar Cells Displaying External Quantum Efficiencies Exceeding 120%

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• 作者：Marcus L. B枚hm ; Tom C. Jellicoe ; Maxim Tabachnyk ; Nathaniel J. L. K. Davis ; Florencia Wisnivesky-Rocca-Rivarola ; Caterina Ducati ; Bruno Ehrler ; Artem A. Bakulin ; Neil C. Greenham
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：15
• 期：12
• 页码：7987-7993
• 全文大小：384K
• ISSN：1530-6992

文摘

Multiple exciton generation (MEG) in semiconducting quantum dots is a process that produces multiple charge-carrier pairs from a single excitation. MEG is a possible route to bypass the Shockley-Queisser limit in single-junction solar cells but it remains challenging to harvest charge-carrier pairs generated by MEG in working photovoltaic devices. Initial yields of additional carrier pairs may be reduced due to ultrafast intraband relaxation processes that compete with MEG at early times. Quantum dots of materials that display reduced carrier cooling rates (e.g., PbTe) are therefore promising candidates to increase the impact of MEG in photovoltaic devices. Here we demonstrate PbTe quantum dot-based solar cells, which produce extractable charge carrier pairs with an external quantum efficiency above 120%, and we estimate an internal quantum efficiency exceeding 150%. Resolving the charge carrier kinetics on the ultrafast time scale with pump鈥損robe transient absorption and pump鈥損ush鈥損hotocurrent measurements, we identify a delayed cooling effect above the threshold energy for MEG.