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Title: Quantum funneling in blended multi-band gap core/shell colloidal quantum dot solar cells

Multi-band gap heterojunction solar cells fabricated from a blend of 1.2‚ÄČeV and 1.4‚ÄČeV PbS colloidal quantum dots (CQDs) show poor device performance due to non-radiative recombination. To overcome this, a CdS shell is epitaxially formed around the PbS core using cation exchange. From steady state and transient photoluminescence measurements, we understand the nature of charge transfer between these quantum dots. Photoluminescence decay lifetimes are much longer in the PbS/CdS core/shell blend compared to PbS only, explained by a reduction in non-radiative recombination resulting from CdS surface passivation. PbS/CdS heterojunction devices sustain a higher open-circuit voltage and lower reverse saturation current as compared to PbS-only devices, implying lower recombination rates. Further device performance enhancement is attained by modifying the composition profile of the CQD species in the absorbing layer resulting in a three dimensional quantum cascade structure.
Authors:
; ;  [1] ; ; ;  [2]
  1. Department of Materials, University of Oxford, 16 Parks Road, OX1 3PH Oxford (United Kingdom)
  2. Department of Physics, Clarendon Laboratory, Parks Road, OX1 3PU Oxford (United Kingdom)
Publication Date:
OSTI Identifier:
22482060
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CADMIUM SULFIDES; EPITAXY; HETEROJUNCTIONS; ION EXCHANGE; LEAD SULFIDES; PASSIVATION; PHOTOLUMINESCENCE; QUANTUM DOTS; SATURATION; SOLAR CELLS; SURFACES