Ligand Exchange at a Covalent Surface Enables Balanced Stoichiometry in III-V Colloidal Quantum Dots

Min Jae Choi, Laxmi Kishore Sagar, Bin Sun, Margherita Biondi, Seungjin Lee, Amin Morteza Najjariyan, Larissa Levina, F. Pelayo García De Arquer, Edward H. Sargent

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

III-V colloidal quantum dots (CQDs) are promising semiconducting materials for optoelectronic applications; however, their strong covalent character requires a distinct approach to surface management compared with widely investigated II-VI and IV-VI CQDs-dots, which by contrast are characterized by an ionic nature. Here we show stoichiometric reconstruction in InAs CQDs by ligand exchange. In particular, we find that indium-carboxylate ligands, which passivate as-synthesized InAs CQDs and are responsible for In-rich surfaces, can be replaced by anionic ligands such as thiols. This enables the production of inks consisting of balanced-stoichiomety CQDs; this is distinct from what is observed in II-VI and IV-VI CQDs, in which thiols replace carboxylates. The approach enables the implementation of InAs CQD solids as the active layer in photodiode detectors that exhibit an external quantum efficiency of 36% at 930 nm and a photoresponse time of 65 ns, which is 4 times shorter than that of reference PbS CQD devices.

Original languageEnglish
Pages (from-to)6057-6063
Number of pages7
JournalNano Letters
Volume21
Issue number14
DOIs
StatePublished - 28 Jul 2021

Keywords

  • covalent surface
  • III-V colloidal quantum dots
  • ligand exchange
  • photodetector
  • stoichiometry

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