jz7b01503_si_001.pdf (30.91 kB)
Ultrafast Carrier Trapping in Thick-Shell Colloidal Quantum Dots
journal contribution
posted on 2017-06-21, 00:00 authored by Ankit Jain, Oleksandr Voznyy, Marek Korkusinski, Pawel Hawrylak, Edward H. SargentIt 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.