Lead Telluride Quantum Dot Solar Cells Displaying External Quantum Efficiencies Exceeding 120%.
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-probe transient absorption and pump-push-photocurrent measurements, we identify a delayed cooling effect above the threshold energy for MEG.
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Marcus L
ML
Böhm
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Tom C
TC
Jellicoe
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Maxim
M
Tabachnyk
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Nathaniel J L K
NJ
Davis
Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge, CB3 0FS, United Kingdom.
Florencia
F
Wisnivesky-Rocca-Rivarola
Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge, CB3 0FS, United Kingdom.
Caterina
C
Ducati
Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG, Amsterdam, The Netherlands.
Bruno
B
Ehrler
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Artem A
AA
Bakulin
Cavendish Laboratory, University of Cambridge , J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom.
Neil C
NC
Greenham
Lead telluride quantum dots; multiple exciton generation; pump−push photocurrent spectroscopy; solar cells