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All-inorganic α-CsPbBrx I3-x perovskites featuring nano-sized crystallites show great potential for pure-red light-emitting diode (LED) applications. Currently, the CsPbBrx I3-x LEDs based on nano-sized α-CsPbBrx I3-x crystallites have been fabricated mainly via the classical colloidal route including a tedious procedure of nanocrystal synthesis, purification, ligand or anion exchange, film casting, etc. With the usually adopted conventional LED device structure, only high turn-on voltages (> 2.7) have been achieved for CsPbBrx I3-x LEDs. Moreover, this mix-halide system may suffer from severe spectra-shift under bias. In this report, CsPbBrx I3-x thin films featuring nano-sized crystallites are prepared by incorporating multiple ammonium ligands in a one-step spin-coating route. The multiple ammonium ligands constrain the growth of CsPbBrx I3-x nanograins. Such CsPbBrx I3-x thin films benefit from quantum confinement. The corresponding CsPbBrx I3-x LEDs, adopting a conventional LED structure of indium-doped tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/CsPbBrx I3-x /[6,6]-phenyl C61 butyric acid methyl ester (PCBM)/ bathocuproine (BCP)/Al, emit pure-red color at Commission Internationale de l'éclairage (CIE) coordinates of (0.709, 0.290), (0.711, 0.289), etc., which represent the highest color-purity for reported pure-red perovskite LEDs and meet the Rec. 2020 requirement at CIE (0.708, 0.292) very well. The CsPbBrx I3-x LED shows a low turn-on voltage of 1.6 V, maximum external quantum efficiency of 8.94%, high luminance of 2,859 cd·m-2, and good color stability under bias.

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Publication history

Received: 17 June 2020
Revised: 20 August 2020
Accepted: 22 August 2020
Published: 05 January 2021
Issue date: January 2021

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© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature

Acknowledgements

This work was supported by funding from the Energy Materials and Surface Sciences Unit of the Okinawa Institute of Science and Technology Graduate University (OIST), the OIST Proof of Concept (POC) Program, the OIST R&D Cluster Research Program, and the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research [KAKENHI] (No. JP18K05266).

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Email: nanores@tup.tsinghua.edu.cn

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