Photon upconversion employing semiconductor nanocrystals (NCs) makes use of their large and tunable absorption to harvest light in the near-infrared (NIR) wavelengths as well as their small gap between singlet and triplet excited states to reduce energy losses. Here, we report the highest QY (11.8%) thus far for the conversion of NIR to yellow photons by improving the quality of the PbS NC. This high QY was achieved by using highly purified lead and thiourea precursors. This QY is 2.6 times higher than from NCs prepared with commercially available lead and sulfide precursors. Transient absorption spectroscopy reveals two reasons for the enhanced QY: longer intrinsic exciton lifetimes of PbS NCs and the ability to support a longer triplet lifetime for the surface-bound transmitter molecule. Overall, this results in a higher efficiency of triplet exciton transfer from the PbS NC light absorber to the emitter and thus a higher photon upconversion QY.
|Number of pages||4|
|Journal||Journal of the American Chemical Society|
|State||Published - Jun 26 2019|
Bibliographical noteFunding Information:
M.L.T. acknowledges the Alfred P. Sloan foundation. The U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Solar Photochemistry Program Award Numbers DE-FG02-12ER16347 to T.L and DE-SC0018969 to M.L.T supported this work. Z.L. and K.R.G. contributed the XPS measurements under work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences and the EPSCoR program, under Award Number DE-SC0018208.
Copyright © 2019 American Chemical Society.
ASJC Scopus subject areas
- Chemistry (all)
- Colloid and Surface Chemistry