Issue 30, 2020

Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite

Abstract

In this work, we have studied new double perovskite materials, A21+B2+B3+X61−, where A21+ = Cs, B2+ = Li, Na, B3+ = Al, Ga, In, and X61−. We used the all electron full-potential linearized augmented plane wave (FP-LAPW+lo) method within the framework of density functional theory. We used the mBJ approximation and WC-GGA as exchange–correlation functionals. We optimized the lattice constants with WC-GGA. Band structures were calculated with and without spin–orbit coupling (SOC). Further, band structures for Cs2LiGaBr6 and Cs2NaGaBr6 were calculated with SOC + mBJ to correct the band gap values with respect to experimental value. We obtained direct bandgaps at Γ-point of 1.966 eV for Cs2LiGaBr6 and 1.762 eV for Cs2NaGaBr6, which are similar to the parent organic–inorganic perovskite (MAPI) CH3NH3PbI3 (Eg = 1.6 eV). Total and partial density of states were analyzed to understand the orbital contribution of Cs, Na, Li, Ga and Br near the Fermi level. The optical properties in terms of real and imaginary ε, refractive index n, extinction coefficient k, optical conduction σ, absorption I, and reflectivity R were calculated. A study of the elastic and mechanical properties shows that both materials are thermodynamically stable. A stable, direct bandgap and a gap value close to those of MAPI make Cs2NaGaBr6 a great competitor in the Pb-free hybrid perovskite solar cells world.

Graphical abstract: Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite

Associated articles

Article information

Article type
Paper
Submitted
24 Feb 2020
Accepted
28 Apr 2020
First published
05 May 2020
This article is Open Access
Creative Commons BY license

RSC Adv., 2020,10, 17444-17451

Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite

Y. Saeed, B. Amin, H. Khalil, F. Rehman, H. Ali, M. I. Khan, A. Mahmood and M. Shafiq, RSC Adv., 2020, 10, 17444 DOI: 10.1039/D0RA01764G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements