A Facet-Specific Quantum Dot Passivation Strategy for Colloid Management and Efficient Infrared Photovoltaics

Younghoon Kim, Fanglin Che, Jea Woong Jo, Jongmin Choi, F. Pelayo García de Arquer, Oleksandr Voznyy, Bin Sun, Junghwan Kim, Min Jae Choi, Rafael Quintero-Bermudez, Fengjia Fan, Chih Shan Tan, Eva Bladt, Grant Walters, Andrew H. Proppe, Chengqin Zou, Haifeng Yuan, Sara Bals, Johan Hofkens, Maarten B.J. RoeffaersSjoerd Hoogland, Edward H. Sargent*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Colloidal nanocrystals combine size- and facet-dependent properties with solution processing. They offer thus a compelling suite of materials for technological applications. Their size- and facet-tunable features are studied in synthesis; however, to exploit their features in optoelectronic devices, it will be essential to translate control over size and facets from the colloid all the way to the film. Larger-diameter colloidal quantum dots (CQDs) offer the attractive possibility of harvesting infrared (IR) solar energy beyond absorption of silicon photovoltaics. These CQDs exhibit facets (nonpolar (100)) undisplayed in small-diameter CQDs; and the materials chemistry of smaller nanocrystals fails consequently to translate to materials for the short-wavelength IR regime. A new colloidal management strategy targeting the passivation of both (100) and (111) facets is demonstrated using distinct choices of cations and anions. The approach leads to narrow-bandgap CQDs with impressive colloidal stability and photoluminescence quantum yield. Photophysical studies confirm a reduction both in Stokes shift (≈47 meV) and Urbach tail (≈29 meV). This approach provides a ≈50% increase in the power conversion efficiency of IR photovoltaics compared to controls, and a ≈70% external quantum efficiency at their excitonic peak.

Original languageEnglish
Article number1805580
JournalAdvanced Materials
Volume31
Issue number17
DOIs
StatePublished - 25 Apr 2019

Keywords

  • colloidal quantum dots
  • facet-specific passivation
  • infrared solar cells
  • narrow bandgap
  • sodium acetate

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