Surface band bending and carrier dynamics in colloidal quantum dot solids

Philippa Clark, Nathan Lewis, Jack Chun-Ren Ke, Ruben Ahumada Lazo, Qian Chen, Darren Neo, E. Ashley Gaulding, Gregory F. Pach, Igor Pis, Mathieu G. Silly, Wendy Flavell

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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 languageEnglish
Publication statusPublished - 19 Oct 2021

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  • Photon Science Institute


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