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Charge dynamics at heterojunctions for PbS/ZnO colloidal quantum dot solar cells probed with time-resolved surface photovoltage spectroscopy
Author(s) -
Ben F. Spencer,
Marina A. Leontiadou,
Pip C. J. Clark,
Andrew I. Williamson,
Mathieu G. Silly,
Fausto Sirotti,
Simon M. Fairclough,
Shik Chi Edman Tsang,
Darren C. J. Neo,
Hazel E. Assender,
Andrew A. R. Watt,
Wendy R. Flavell
Publication year - 2016
Publication title -
applied physics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 442
eISSN - 1077-3118
pISSN - 0003-6951
DOI - 10.1063/1.4943077
Subject(s) - heterojunction , surface photovoltage , quantum dot , materials science , spectroscopy , substrate (aquarium) , optoelectronics , photoconductivity , charge carrier , depletion region , photoemission spectroscopy , band gap , laser , x ray photoelectron spectroscopy , semiconductor , analytical chemistry (journal) , chemistry , optics , physics , oceanography , nuclear magnetic resonance , quantum mechanics , chromatography , geology
Time-resolved laser-pump X-ray-photoemission-probe spectroscopy of a ZnO (101¯0) substrate with and without PbSquantum dots(QDs) chemically linked to the surface is performed, using laser photonenergies resonant with and below the band gapenergy of the substrate (λ = 372 and 640 nm, hν = 3.33 and 1.94 eV). Charge injection from the photoexcitedQDs to ZnO is demonstrated through the change in the surface photovoltage of the ZnO substrate observed when the heterojunction is illuminated with 1.94 eV radiation. The measured carrier dynamics are limited by the persistent photoconductivity of ZnO, giving dark carrier lifetimes of the order of 200 μs in a depletion layer at the interface. The chemical specificity of soft X-rays is used to separately measure the charge dynamics in the quantum dots and the substrate, yielding evidence that the depletion region at the interface extends into the PbSQD layer

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