Tuning the Physical Properties of Lead-Free Halide Double Perovskite Cs₂MInCl₆ (M = Na, K) via Cu Doping for Optoelectronic Applications: ADFT Investigation

Abstract

Lead-free halide double perovskites (DPs) have gained remarkable attention as potential materials for optoelectronic applications due to their outshining electronic and optical properties, stability, and nontoxicity. First-principles calculations on the structural, electronic, optical, and mechanical properties of Cs 2 Na 1−x Cu x InCl 6 and Cs 2 K 1−x Cu x InCl 6 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) double perovskites are investigated employing density functional theory. The formability factors and decomposition enthalpies confirm the structural and thermodynamic stability of the compounds. Only the Cs 2 CuInCl 6 compound shows instability in terms of the octahedral factor, tolerance factor, and decomposition enthalpy. The band structures are obtained by using both generalized gradient approximation Perdew−Burke−Ernzerhof (GGA-PBE) and the HSE06 functional. The band gap of materials was reduced with increasing Cu content in Cs 2 MInCl 6 (M = Na, K), which made the materials a better candidate for optoelectronic devices. The density of states and optical properties are also computed by the HSE06 method to correspond with the band structure. The different parameters of the optical properties support the electronic properties of the materials. Increasing the copper doping concentration in the pure Cs 2 MInCl 6 compound produces better optical activity in the visible region, implicating the materials in photovoltaics technology. Based on the components of the stiffness tensor, Cs 2 MInCl 6 , Cs 2 M 0.75 Cu 0.25 InCl 6 , and Cs 2 M 0.50 Cu 0.50 InCl 6 DPs ascertain the mechanical stability. On the other hand, Cs 2 M 0.25 Cu 0.75 InCl 6 and Cs 2 CuInCl 6 compounds are mechanically unstable. The Cs 2 NaInCl 6 double perovskite (DP) is brittle in nature, but the Cu-doped Cs 2 NaInCl 6 crystal systems follow ductility. In the case of K-based materials, all of the Cs 2 K 1−x Cu x InCl 6 (x = 0.00, 0.25, 0.75, and 1.00) DPs are ductile in nature, except the Cs 2 K 0.50 Cu 0.50 InCl 6 material, which displays brittleness.

Effect of metal (Cr, Sr, Ag, Cu) doping on the performance of lead-free RbSnI3 based perovskite solar cells: A theoretical approach

“…Orthorhombic RbSnI 3 exhibits an indirect band gap at room temperature, making it inappropriate for solar cell devices [13]. However, by incorporating an appropriate metal dopant into a single halide RbSnI 3 , the band gap can be significantly decreased with relatively faster electron transport between cation and divalent materials, making it a potential candidate for an efficient absorber of visible light energy [14][15][16]. In the case of SrTiO 3 perovskite, Cu-doping has been identified as a promising approach for photovoltaic applications because of its enhanced stability at high temperatures and in oxidizing environments [17][18][19].…”