Charge dynamics at heterojunctions for PbS/ZnO colloidal quantum dot solar cells probed with time-resolved surface photovoltage spectroscopy

• DOI: 10.1063/1.4943077
• Publication Date: 2016-03-01T18:00:27Z
• Authors: B. F. Spencer; M. A. Leontiadou; P. C. J. Clark; A. I. Williamson; M. G. Silly; F. Sirotti; S. M. Fairclough; S. C. E. Tsang; D. C. J. Neo; H. E. Assender; A. A. R. Watt; W. R. Flavell
• Keywords: Surface Photovoltage; Photoconductivity; Charge carrier; Depletion region

Time-resolved laser-pump X-ray-photoemission-probe spectroscopy of a ZnO (101¯0) substrate with and without PbS quantum dots (QDs) chemically linked to the surface is performed, using laser photon energies resonant below band gap energy (λ = 372 640 nm, hν 3.33 1.94 eV). Charge injection from photoexcited QDs demonstrated through change in photovoltage observed when heterojunction illuminated eV radiation. The measured carrier dynamics are limited by persistent photoconductivity ZnO, giving dark lifetimes order 200 μs depletion layer at interface. chemical specificity soft X-rays used separately measure charge substrate, yielding evidence that region interface extends into QD layer.