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Acid-Assisted Ligand Exchange Enhances Coupling in Colloidal Quantum Dot Solids
- Acid-Assisted Ligand Exchange Enhances Coupling in Colloidal Quantum Dot Solids
- Jo, Jea Woong; Choi, Jong Min; de Arquer, F. Pelayo Garcia; Seifitokaldani, Ali; Sun, Bin; Kim, Younghoon; Ahn, Hyung Ju; Fan, James; Quintero-Bermudez, Rafael; Kim, Jung Hwan; Choi, Min Jae; Baek, Se Woong; Proppe, Andrew H.; Walters, Grant; Nam, Dae-Hyun; Kelley, Shana; Hoogland, Sjoerd; Voznyy, Oleksandr; Sargent, Edward H.
- DGIST Authors
- Kim, Younghoon; Nam, Dae-Hyun
- Issue Date
- Nano Letters, 18(7), 4417-4423
- Article Type
- Author Keywords
- Colloidal quantum dots; photovoltaics; solution-phase ligand exchange; narrow bandgap; infrared; surface passivation
- LIGHT-EMITTING-DIODES; SOLAR-CELLS; PBS NANOCRYSTALS; INFRARED PHOTOVOLTAICS; INKS; SURFACE; SIZE
- Colloidal quantum dots (CQDs) are promising solution-processed infrared-absorbing materials for optoelectronics. In these applications, it is crucial to replace the electrically insulating ligands used in synthesis to form strongly coupled quantum dot solids. Recently, solution-phase ligand-exchange strategies have been reported that minimize the density of defects and the polydispersity of CQDs; however, we find herein that the new ligands exhibit insufficient chemical reactivity to remove original oleic acid ligands completely. This leads to low CQD packing and correspondingly low electronic performance. Here we report an acid-assisted solution-phase ligand-exchange strategy that, by enabling efficient removal of the original ligands, enables the synthesis of densified CQD arrays. Our use of hydroiodic acid simultaneously facilitates high CQD packing via proton donation and CQD passivation through iodine. We demonstrate highly packed CQD films with a 2.5 times increased carrier mobility compared with prior exchanges. The resulting devices achieve the highest infrared photon-to-electron conversion efficiencies (>50%) reported in the spectral range of 0.8 to 1.1 eV. © 2018 American Chemical Society.
- American Chemical Society
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- Division of Energy Technology1. Journal Articles
Department of Energy Science and EngineeringRenewable Energy Conversion Materials Laboratory1. Journal Articles
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