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Scientists Reveal Dynamics Mechanism of Lead-free Na-In Double Perovskite Nanocrystals
  English.dicp.cas.cn    Posted:2019-10-08    From:Group 1101

A research team led by HAN Keli from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences synthesized undoped and Ag-doped lead-free double perovskite nanocrystals (NCs) by variable temperature hot injection. Ag-doped NCs exhibited bright yellow emission, and the dynamics mechanism was further clarified. Their findings were published in Angew. Chem. Int. Ed..

Lead-free halide perovskite NCs have drawn wide attentions and become a hot topic of current research due to non-toxicity and stability. In particular, indium-based double perovskite NCs with three-dimensional structure and direct bandgap are considered to be the ideal light emitting materials in the illumination field.

However, the photoluminescence quantum efficiency (PLQE) of undoped In-based NCs is still very low since the mechanism is unclear. This problem restricts the design and development of new and efficient perovskite materials.

PL spectrum and HRTEM image of the Cs2NaInCl6:10% Ag NCs. (Image by HAN Peigeng)

The scientists synthesized high-quality undoped and Ag-doped lead-free direct bandgap Na-In-based double perovskite NCs by novel variable temperature hot injection. This method was universal for lead-free perovskites NCs.

Scientists found that the Cs2NaInCl6 NCs had little photoluminescence attributed to dark self-trapped excitons (STEs). And the doping Ag+ cations could not only make a transition from dark STEs state to bright STEs state, but also passivate defects. Thus, the Cs2NaInCl6: Ag NCs exhibited bright yellow emission with the highest PLQE of 31.1% and excellent stability.

The STEs dynamics mechanism was further studied through ultrafast transient absorption (TA) techniques.

This work highlights the importance of synthesis method optimization and proper element doping for the design of new semiconductor NCs, and provides a new and feasible way to search for new high-performance nano materials in optoelectronic applications.

This study was supported by the key research project of National Natural Science Foundation. (Text by HAN Peigeng)

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