Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

Abstract

The highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

Titanium‐Based Vacancy‐Ordered Double Halide Family in Perovskite Solar Cells

“…Alternative compositional and structural derivatives of the perovskite family, specifically double halide perovskites (elpasolite) (general formula: A 2 B 1+ B 3+ X 6 ) [ 15 ] and vacancy‐ordered double halide perovskite (general formula: A 2 BX 6 ), [ 16 ] have been recently explored in overcoming the instability and toxicity issues of Pb‐based perovskites. [ 17 ] Double halide perovskites (DHPs) and vacancy‐ordered DHPs are a structural derivative of the archetypal perovskite structure (ABX 3 ).…”

“…The A 2 BX 6 structure shows similar features to ABX 3 perovskites, mostly of cubic structures. [ 16 ] Whereby A corresponds to the organic/inorganic cation, whereas B and X represent the metal cation and halogen ion, respectively. [ 21 ] Vacancy‐ordered DHPs possess a rich compositional, structural, and dynamic phase space that may be accessed and tuned by compositional modification at all three sites (A, B, X) in obtaining desirable optical and electronic properties.…”

First-Principles Density Functional Theory Study of Modified Germanene-Based Electrode Materials

“…However, the C Q of germanene-based electrodes materials for supercapacitors has not been fully studied. In the application process and/or growth conditions, the introduction of vacancy defects [ 32 , 33 , 34 ], doping/co-doping [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ], and adsorbents [ 42 , 43 ] could alter the electronic structure, thereby affecting the quantum capacitance. Furthermore, the randomness of defects/doping had an influence on the electronic and transport properties, for example, edge defects have an effect on the transport gap [ 44 , 45 ].…”

Photocatalytic reduction of CO2by halide perovskites: recent advances and future perspectives

“…In APbX 3 NC systems, the lead toxicity and its bioaccumulation in the ecosystem are known as a key drawback, which in turn motivate the researcher to find out alternative materials with similar optoelectronic characteristics, such as Cs 2 SnI 6 NCs. [119][120][121] To date, there has been very little success. Cs 2 SnI 6 crystallizes in the face-centered cubic structure.…”

“…A Cs 2 SnI 6 structure is a perovskite derivative that is made by removing half of the Sn atoms at regular intervals from each center of the [SnI 6 ] octahedron. 120 Because of this, the structure is also known as a "vacancy ordered double perovskite." Two primary techniques are now being explored in the search for leadfree metal halide compounds: a "simple" substitution of Pb 2+ cations with other less toxic divalent metal ions from the same group IV, such as Sn or Ge; and a "complex" substitution of Pb 2+ cations with other less toxic divalent metal ions from the same group IV, 122 such as Sn or Ge or a substitution of one monovalent M + and one trivalent M 3+ cation for every two divalent Pb 2+ ions (i.e., 2Pb 2+ → B + + B 3+ ), resulting in quaternary A 2 B + B 3+ X 6 systems also known as "double perovskites" in Figure 6f.…”