CdS/ZnS core-shell nanocrystal photosensitizers for visible to UV upconversion
Journal article, 2017

Herein we report the first example of nanocrystal (NC) sensitized triplet-triplet annihilation based photon upconversion from the visible to ultraviolet (vis-to-UV). Many photocatalyzed reactions, such as water splitting, require UV photons in order to function efficiently. Upconversion is one possible means of extending the usable range of photons into the visible. Vis-to-UV upconversion is achieved with CdS/ZnS core-shell NCs as the sensitizer and 2,5-diphenyloxazole (PPO) as annihilator and emitter. The ZnS shell was crucial in order to achieve any appreciable upconversion. From time resolved photoluminescence and transient absorption measurements we conclude that the ZnS shell affects the NC and triplet energy transfer (TET) from NC to PPO in two distinct ways. Upon ZnS growth the surface traps are passivated thus increasing the TET. The shell, however, also acts as a tunneling barrier for TET, reducing the efficiency. This leads to an optimal shell thickness where the upconversion quantum yield (Phi(UC)') is maximized. Here the maximum Phi(UC)' was determined to be 5.2 +/- 0.5% for 4 monolayers of ZnS shell on CdS NCs.

Author

Victor Gray

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

P. Xia

University of California

Z. Y. Huang

University of California

E. Moses

University of California

A. Fast

University of California at Irvine (UCI)

D. A. Fishman

University of California at Irvine (UCI)

V. I. Vullev

University of California

Maria Abrahamsson

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry, Physical Chemistry

Kasper Moth-Poulsen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

M. L. Tang

University of California

Chemical Science

2041-6520 (ISSN) 2041-6539 (eISSN)

Vol. 8 8 5488-5496

Subject Categories

Atom and Molecular Physics and Optics

DOI

10.1039/c7sc01610g

More information

Latest update

5/17/2018