Identifying and Eliminating Emissive Sub-bandgap States in Thin Films of PbS Nanocrystals.

Hwang, Gyu Weon; Kim, Donghun; Cordero, Jose M; Wilson, Mark W B; Chuang, Chia-Hao M; Grossman, Jeffrey C; Bawendi, Moungi G · Adv Mater · 2015

basic_science · Level V

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Abstract

Chemical oxidation of under-charged Pb atoms reduces the density of trap states by a factor of 40 in films of colloidal PbS quantum dots for devices. These emissive sub-bandgap states are a byproduct of several standard ligand-exchange procedures. X-ray photoelectron spectro-scopy measurements and density function theory simulations demonstrate that they are associated with under-charged Pb.