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Increased carrier mobility and lifetime in CdSe quantum dot thin films through surface passivation and doping



Daniel Straus, E. D. Goodwin, E. A. Gaulding, Shinichiro Muramoto, Murray B. Christopher, Cherie R. Kagan


Passivating surface defects and controlling the carrier concentration and mobility in quantum dot (QD) thin films is a prerequisite to designing electronic and optoelectronic devices. We investigate the effect of introducing indium in CdSe QD thin films on the dark mobility and the photogenerated carrier mobility and lifetime using field-effect transistor (FET) and time-resolved microwave conductivity (TRMC) measurements. We uniformly evaporate films of indium ranging from 1 nm to 11 nm in thickness on top of approximately 40 nm thick, thiocyanate-capped, CdSe QD thin films and anneal the samples at 300 oC, to densify the film by decomposing the thiocyanate to sulfide and drive diffusion of indium through the QD film thickness. The introduction of indium passivates surface states, dopes the QD thin films, and preserves quantum confinement, compared to QD thin films annealed in the absence of indium. As the amount of indium used to dope the film increases, the FET and TRMC mobilities and the TRMC lifetime increase. Films doped with 9 nm and 11 nm of indium are degenerately n-doped. The increase in mobility and lifetime is consistent with increased indium passivating mid-gap and band-tail trap states and doping the films, shifting the Fermi energy closer to and into the conduction band.
Journal of Physical Chemistry Letters


Straus, D. , Goodwin, E. , Gaulding, E. , Muramoto, S. , Christopher, M. and Kagan, C. (2015), Increased carrier mobility and lifetime in CdSe quantum dot thin films through surface passivation and doping, Journal of Physical Chemistry Letters, [online], (Accessed April 23, 2024)
Created November 3, 2015, Updated October 12, 2021