Infrared emitting materials with a large Stokes shift and minimal reabsorption are technologically important for luminescent solar concentrators (LSCs) and for bioimaging applications. The design of III-V quantum dots (QDs) for these applications necessitate the understanding and use of band gap engineering to synthesize core-shell QDs with high photoluminescent quantum efficiency (PLQE) and minimal absorption-photoluminescence (PL) overlap. Earlier reports suggest that the InAs-InP band alignment is quasi type-II in nature but has not been exploited yet to synthesize near infrared (NIR) emitting core-shell QDs with sufficiently high PLQE, large Stokes shift and high photostability for its intended applications. Here, we describe the first realization of two new quaternary giant shell QDs with efficient PL in the NIR: InAs-In(Zn)P-ZnSe-ZnS and In(Zn)As-In(Zn)P-GaP-ZnS. We employ a convenient one-pot, continuous injection approach to achieve the controlled growth of thick In(Zn)P shells around small InAs nuclei. The In(Zn)P shell absorbs strongly across the visible region and subsequent energy transfer to the InAs core affords NIR emission, hence providing a significant Stokes shift and minimal absorption-PL emission overlap. Density functional theory (DFT) calculations reveal a quasi type-II band alignment responsible for the substantial spectral red-shifts during shell growth and elucidated the cationic exchange growth mechanism of GaP over the In(Zn)P shell. Our results provide a highly convenient protocol to synthesize highly luminescent and spectrally tunable NIR core-shell QDs for consumer opto-electronic products and biological applications. We further anticipate that our experimental and computational results will provide scientific insights into future NIR core-shell QD designs.

Multi-core-shell quantum dots for solar harvesting applications

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.