Photoexcited Carrier Dynamics of Cu2S Thin Films.
Copper sulfide is a simple binary material with promising attributes for low-cost thin film photovoltaics. However, stable Cu2S-based device efficiencies approaching 10% free from cadmium have yet to be realized. In this Letter, transient absorption spectroscopy is used to investigate the dynamics of the photoexcited state of isolated Cu2S thin films prepared by atomic layer deposition or vapor-based cation exchange of ZnS. While a number of variables including film thickness, carrier concentration, surface oxidation, and grain boundary passivation were examined, grain structure alone was found to correlate with longer lifetimes. A map of excited state dynamics is deduced from the spectral evolution from 300 fs to 300 μs. Revealing the effects of grain morphology on the photophysical properties of Cu2S is a crucial step toward reaching high efficiencies in operationally stable Cu2S thin film photovoltaics.
§Materials Science Division and ‡Nanoscience and Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
Shannon C
SC
Riha
§Materials Science Division and ‡Nanoscience and Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
Richard D
RD
Schaller
§Materials Science Division and ‡Nanoscience and Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
David J
DJ
Gosztola
§Materials Science Division and ‡Nanoscience and Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
Gary P
GP
Wiederrecht
§Materials Science Division and ‡Nanoscience and Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
Alex B F
AB
Martinson
Cu2S thin films; atomic layer deposition; photophysical properties; photovoltaics; thin film solar cell; transient absorption spectroscopy