Optical properties of ytterbium-doped and undoped Cs2AgInCl6 thin films deposited by co-evaporation of chloride salts

Yukun Liu, Pulkita Jain, Iver J. Cleveland, Minh Tran, Seda Sarp, Kajini Sandrakumar, Rafaella Saa Rodriguez, Eray S. Aydil

Research output: Contribution to journalArticlepeer-review


The double halide perovskite Cs2AgInCl6, first synthesized in 2017, is a potential lead-free alternative to CsPbCl3 for optoelectronic applications, but its discovery is recent, there are knowledge gaps and controversies in its optical properties, and its formation as a thin film for practical use remains difficult due to the poor solubility of the precursors used in solution synthesis. Herein, we report the formation of Cs2AgInCl6 thin films through reactive physical vapor deposition (PVD) via co-evaporation of CsCl, AgCl, and InCl3 for the first time in a solvent-, ligand- and oxygen-free environment. We also doped these films with Yb3+ by co-evaporating YbCl3. Consistent with previous reports, the undoped films emit orange luminescence peaking at 630 nm, while Yb-doped films emit near-infrared (NIR) luminescence at 990 nm. Using the excitation spectrum of the orange and NIR emissions from the Yb3+ dopant and absorbance spectra, we determine the Cs2AgInCl6 band gap to be 3 eV. Up to 12% (of Ag or In lattice positions) Yb could be incorporated into the film without disrupting its cubic crystal structure or stability. The highest NIR photoluminescence quantum yield was 20%, achieved in films doped with 8% Yb. We show that the emission at 630 nm, previously assigned to self-trapped excitons in Cs2AgInCl6 persists, shifted only slightly (10 s of nm), in Cs2AgBiCl6, Cs2AgBiBr6, and Cs2NaBiCl6, double perovskites with significantly different band gaps, suggesting that at least some of this emission intensity is due to a common defect, possibly In and Bi antisite defects, and not necessarily only due to self-trapped excitons.

Original languageEnglish (US)
Pages (from-to)21099-21108
Number of pages10
JournalJournal of Materials Chemistry A
Issue number39
StatePublished - Sep 7 2023

ASJC Scopus subject areas

  • General Chemistry
  • Renewable Energy, Sustainability and the Environment
  • General Materials Science


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