Optimizing surface chemistry of PbS colloidal quantum dot for highly efficient and stable solar cells via chemical binding

Long Hu, Qi Lei, Xinwei Guan, Robert Patterson, Jianyu Yuan, Chun-Ho Lin, Jiyun Kim, Xun Geng, Adnan Younis, Xianxin Wu, Xinfeng Liu, Tao Wan, Dewei Chu, Tom Wu*, Shujuan Huang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
1 Downloads (Pure)

Abstract

The surface chemistry of colloidal quantum dots (CQD) play a crucial role in fabricating highly efficient and stable solar cells. However, as-synthesized PbS CQDs are significantly off-stoichiometric and contain inhomogeneously distributed S and Pb atoms at the surface, which results in undercharged Pb atoms, dangling bonds of S atoms and uncapped sites, thus causing surface trap states. Moreover, conventional ligand exchange processes cannot efficiently eliminate these undesired atom configurations and defect sites. Here, potassium triiodide (KI3) additives are combined with conventional PbX2 matrix ligands to simultaneously eliminate the undercharged Pb species and dangling S sites via reacting with molecular I2 generated from the reversible reaction KI3 ⇌ I2 + KI. Meanwhile, high surface coverage shells on PbS CQDs are built via PbX2 and KI ligands. The implementation of KI3 additives remarkably suppresses the surface trap states and enhances the device stability due to the surface chemistry optimization. The resultant solar cells achieve the best power convention efficiency of 12.1% and retain 94% of its initial efficiency under 20 h continuous operation in air, while the control devices with KI additive deliver an efficiency of 11.0% and retains 87% of their initial efficiency under the same conditions.

Original languageEnglish
Article number2003138
Pages (from-to)1-9
Number of pages9
JournalAdvanced Science
Volume8
Issue number2
Early online date27 Nov 2020
DOIs
Publication statusPublished - 20 Jan 2021

Bibliographical note

Copyright the Author(s) 2020. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • chemical binding
  • PbS colloidal quantum dots
  • solar cells
  • surface chemistry

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