title: Near-unity quantum yields from chloride treated CdTe colloidal quantum dots.
abstract: Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. This process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours.
authors.affiliation: FRS, School of Chemistry, University of Manchester, Manchester, M13 9PL, UK.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Page
authors.forename: Daniel
authors.initials: D
authors.lastname: Espinobarro-Velazquez
authors.forename: Marina A
authors.initials: MA
authors.lastname: Leontiadou
authors.forename: Charles
authors.initials: C
authors.lastname: Smith
authors.forename: Edward A
authors.initials: EA
authors.lastname: Lewis
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Haigh
authors.forename: Chen
authors.initials: C
authors.lastname: Li
authors.forename: Hanna
authors.initials: H
authors.lastname: Radtke
authors.forename: Atip
authors.initials: A
authors.lastname: Pengpad
authors.forename: Federica
authors.initials: F
authors.lastname: Bondino
authors.forename: Elena
authors.initials: E
authors.lastname: Magnano
authors.forename: Igor
authors.initials: I
authors.lastname: Pis
authors.forename: Wendy R
authors.initials: WR
authors.lastname: Flavell
authors.forename: Paul
authors.initials: P
authors.lastname: O'Brien
authors.forename: David J
authors.initials: DJ
authors.lastname: Binks
keywords: colloidal quantum dots; nanocrystalline materials; passivation; photoelectron spectroscopy; photoluminescence; transmission electron microscopy