Band Gap Engineering in Cs2(NaxAg1- x)BiCl6 Double Perovskite Nanocrystals

Raman Singh Lamba; Pooja Basera; Saswata Bhattacharya; Sameer Sapra

doi:10.1021/acs.jpclett.9b02168

Band Gap Engineering in Cs₂(Na_xAg_{1- x})BiCl₆ Double Perovskite Nanocrystals

J Phys Chem Lett. 2019 Sep 5;10(17):5173-5181. doi: 10.1021/acs.jpclett.9b02168. Epub 2019 Aug 22.

Authors

Raman Singh Lamba¹, Pooja Basera², Saswata Bhattacharya², Sameer Sapra¹

Affiliations

¹ Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas , New Delhi 110016 , India.
² Department of Physics , Indian Institute of Technology Delhi , Hauz Khas , New Delhi 110016 , India.

PMID: 31415179
DOI: 10.1021/acs.jpclett.9b02168

Abstract

Lead-free double perovskite materials, A₂M(I)M'(III)X₆, have recently attracted attention as environment-friendly alternatives to lead-based perovskites, APbX₃, because of both rich fundamental science and potential applications. We report band gap tuning via alloying of Cs₂AgBiCl₆ nanocrystals (NCs) with nontoxic, abundant Na. It results in a series of Cs₂Na_xAg_1-xBiCl₆ (x = 0, 0.25, 0.5, 0.75, and 1) double perovskite NCs, leading to increase in optical band gap from 3.39 eV (x = 0) to 3.82 eV (x = 1) and 30-fold increment in weak photoluminescence. The tuning of band gap has been further explored by electronic structure calculation under the framework of density functional theory (DFT). The latter confirms that the increase in band gap is due to reduction of Ag contribution near valence band maxima (VBM) on incorporation of Na ion in place of Ag. These alloyed double perovskites can have useful potential applications in optoelectronic devices.