Unprecedentedly Large Photocurrents in Colloidal PbS Quantum-Dot Solar Cells Enabled by Atomic Layer Deposition of Zinc Oxide Electron Buffer Layer

Hyemin Jo, Jai Kyeong Kim, Junghwan Kim, Tae Yeon Seong, Hae Jung Son, Jeung Hyun Jeong, Hyeonggeun Yu

Research output: Contribution to journalArticlepeer-review

Abstract

Due to the excitonic nature, colloidal PbS quantum-dot solar cells have suffered from lower photocurrent densities than expected from the absorber band gap. The heterojunction between solution-processed ZnO and PbS quantum-dots has been predominantly explored for photovoltaic applications. However, the deeper conduction band minimum of typical PbS quantum-dots than that of solution-processed ZnO imposes a high electron barrier, limiting the short-circuit current densities of the resulting solar cells mostly below 30 mA/cm2. Here, we report that atomic layer deposition (ALD) of ZnO buffer at a low temperature can favor the interfacial band alignment and boost the photocurrent density over 35 mA/cm2 at PbS quantum-dot band gap of 1.18 eV. From our band structure analysis, the electron barrier with ALD-ZnO can be 0.55 eV lower compared to that with sol-gel ZnO. Furthermore, photoactivation of shallow gap states formed by hydroxyl species in ALD-ZnO induces band bending and efficient electron tunneling from PbS to ZnO. Due to the improved band alignment, the device with ALD-ZnO exhibits a significantly enhanced lifetime compared to that with sol-gel ZnO upon constant illumination at 1-sun.

Original languageEnglish
Pages (from-to)13776-13784
Number of pages9
JournalACS Applied Energy Materials
Volume4
Issue number12
DOIs
Publication statusPublished - 2021 Dec 27

Keywords

  • atomic layer deposition
  • colloidal quantum dot
  • photoactivation
  • solar cell
  • zinc oxide

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Electrical and Electronic Engineering
  • Materials Chemistry

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