3 years ago

Ultrafast Carrier Trapping in Thick-Shell Colloidal Quantum Dots

Ultrafast Carrier Trapping in Thick-Shell Colloidal Quantum Dots
Pawel Hawrylak, Edward H. Sargent, Ankit Jain, Marek Korkusinski, Oleksandr Voznyy
It has previously been found that Auger processes can lead to femtosecond carrier trapping in quantum dots, limiting their performance in optoelectronic applications that rely on radiative recombination. Using atomistic simulations, we investigate whether a shell can protect carriers from Auger-assisted trapping. For these studies we investigate CdSe/CdS core–shell quantum dots having total diameters reaching up to 10 nm. We find trapping lifetimes as fast as 1 ps for 2 nm shells, and we report that shells as thick as 6 nm are required to suppress trapping fully. The most efficient recombination mechanism is found to proceed through shallow empty traps, suggesting it can be suppressed by filling the traps through doping or external electrochemical potential. Our findings suggest that to achieve efficient light emission, surface traps have to be completely eliminated, even in thick-shell quantum dots.

Publisher URL: http://dx.doi.org/10.1021/acs.jpclett.7b01503

DOI: 10.1021/acs.jpclett.7b01503

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