Surface Band Bending and Carrier Dynamics in Colloidal Quantum Dot Solids

Pip Clark, Nathan Lewis, Jack Ke, Ruben Ahumada-Lazo, Qian Chen, Darren Neo, E. Gaulding, Gregory Pach, Igor Pis, Mathieu Silly, Wendy Flavell

Research output: Contribution to journalArticlepeer-review

4 Scopus Citations


Band bending in colloidal quantum dot (CQD) solids has become important in driving charge carriers through devices. This is typically a result of band alignments at junctions in the device. Whether band bending is intrinsic to CQD solids, i.e. is band bending present at the surface-vacuum interface, has previously been unanswered. Here we use photoemission surface photovoltage measurements to show that depletion regions are present at the surface of n and p-type CQD solids with various ligand treatments (EDT, MPA, PbI2, MAI/PbI2). Using laser-pump photoemission-probe time-resolved measurements, we show that the timescale of carrier dynamics in the surface of CQD solids can vary over at least 6 orders of magnitude, with the fastest dynamics on the order of microseconds in PbS-MAI/PbI2 solids and on the order of seconds for PbS-MPA and PbS-PbI2. By investigating the surface chemistry of the solids, we find a correlation between the carrier dynamics timescales and the presence of oxygen contaminants, which we suggest are responsible for the slower dynamics due to deep trap formation.

Original languageAmerican English
Pages (from-to)17793-17806
Number of pages14
Issue number42
StatePublished - 14 Nov 2021

Bibliographical note

Publisher Copyright:
© The Royal Society of Chemistry.

NREL Publication Number

  • NREL/JA-5K00-81149


  • band bending
  • carriers
  • lead sulfide
  • ligands
  • PbS
  • perovskites
  • quantum dots
  • surface chemistry
  • XPS


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