Structural stability, mechanical, and optoelectronic properties of A2TlBiI6 (A = Cs and Rb) for energy harvesting: A first principles investigation

Cs2TlRhX6 (X = Cl, Br, I): promising halide double perovskites for efficient energy harvesting in photovoltaic and thermoelectric applications

“…Table 3 shows our estimated values of ε 1 (0) for Cs 2 TlRhX 6 (X = Cl, Br, I), where it can be observed that ε 1 (0) increases from Cl to I. This demonstrates the Penn model, commonly known as the inverse relationship between the bandgap and ε1(0), which has been observed for different kinds of materials [15]. The frequency of the ε1(ω) (of these compounds rises from zero to its highest value before falling.…”

“…The Kohn-Sham equation was solved to obtain the properties of the ground state, and for this purpose, the single anonymous term exchange-correlation potential was approximated using various techniques such as the PBEsol functional for structural properties and the Tran Blaha modified Becke-Johnson (TBmBJ) for electronic and optical properties [12][13][14]. The unit cell volume consists of two regions: muffin tin spheres, which exhibit atomic-like characteristics in the wave function, and the interstitial space, which employs a plane wave basis set [15,16]. Convergence criteria were set as follows: angular momenta (ℓ = 12), cutoff energy (−6.0 Ry), Gaussian parameter (Gmax = 12), RKmax = 8, and 2×10 3 k-points in the reciprocal lattice over the Brillouin zone.…”

“…The cubic phase of double halide perovskites Cs 2 TlRhX 6 (X = Cl, Br, I) with space group ̅ Fm 3 m (225) are crystallized, and the actual lattice constants a o (Å) of relaxed structures are computed by using PBEsol potential. We have drawn the energy volume graph using the Brich-Murnaghan equation of states [15]. The computed Bulk modulus and lattice constant are inversely related to one another, as seen in table 1.…”

“…By substituting Br for Cl and I for Br, the bulk modulus B 0 falls from 37.79365 GPa to 32.5270 GPa to 24.47311 GPa due to the increase in the interatomic distance caused by the rise in anionic size, which renders solids less dense. The formulae have been used to calculate the Goldsmith's tolerance factor (t G ), octahedral factor μ and modified tolerance factor τ which is used to determine the structural and thermodynamic stability [15,16]. The Goldsmith's tolerance factor (t G ) has been calculated using the equations to determine the structural and thermodynamic stabilities…”

First-principle investigation of lead-free double perovskites Cs2MScCl6 (M = Na, K) for optoelectronic and thermoelectric applications

“…In order to make up for the lack of such a material, research on lead-free double-perovskite halides (DPH's) has been carried out in recent years [8,9]. Not only do DPH's show enhanced electric conductivity, they have better stability and are more resistant to chemical corrosion than the single perovskites [10][11][12][13].…”