Crystal structure, stability, and optoelectronic properties of the organic-inorganic wide-band-gap perovskite CH3NH3BaI3 : Candidate for transparent conductor applications

Abstract

Structural stability, electronic structure and optical properties of CH3NH3BaI3 hybrid perovskite is examined from theory as well as experiment. Solution-processed thin films of CH3NH3BaI3 exhibited a high transparency in the wavelength range of 400 nm to 825 nm (1.5 eV to 3.1 eV for which the photon current density is highest in the solar spectrum) which essentially justifies a high bandgap of 4 eV obtained by theoretical estimation. Also, the XRD patterns of the thin films match well with the {00l } peaks of the simulated pattern obtained from the relaxed unit cell of CH3NH3BaI3, crystallizing in the I4/mcm space group, with lattice parameters, a = 9.30Å, c = 13.94Å. Atom projected density of state and band structure calculations reveal the conduction and valence band edges to be comprised primarily of Barium d -orbitals and Iodine p-orbitals, respectively. The larger band gap of CH3NH3BaI3 compared to CH3NH3PbI3 can be attributed to the lower electro-negativity coupled with the lack of d -orbitals in the valence band of Ba 2+ . A more detailed analysis reveals the excellent chemical and mechanical stability of CH3NH3BaI3 against humidity, unlike its lead halide counterpart, which degrades under such conditions. We propose La to be a suitable dopant to make this compound a promising candidate for transparent conductor applications, especially for all perovskite solar cells. This claim is supported by our calculated results on charge concentration, effective mass and vacancy formation energies.PACS numbers: 81.10.Dn, 61.50.Ah, 61.10.Nz, 42.70.Qs, Recently, compounds in the organic-inorganic halide perovskite family (AB X 3 : A is an organic cation, B is an inorganic cation, and X is a halide element) have garnered a lot of attention in the solar photovoltaic community. This is due to their superior optoelectronic properties, easy synthesis techniques and variety of compounds that can be obtained via simple substitutions of the A, B and X ions. Specifically, solar cells, with (CH 3 NH 3 ) + as the A cation and Pb 2+ as the B cation, have shown a rapid growth in the solar-to-electricity power conversion efficiency.1-5 The lead halide perovskite solar cell was first introduced by Kojima et al in 2009, wherein it was used in a dye-sensitized solar cell architecture.6 Much of the research in recent times has focused on solid-state cells with different architectures, hole transport layers, compositional engineering, and synthesis techniques.1,3,7-10 Even then, there are some caveats associated with the various components of the CH 3 NH 3 PbX 3 -based solar cells: the stability of the absorber material in ambient conditions and the presence of Pb to name a couple. Active research to address these problems is being conducted worldwide through suitable replacements to both the CH 3 NH 3 and Pb cations.Tunability of the properties by changing the constituent elements gives this class of material more scope of research and applicability.11-13 Such tunability in the bandgap has been observed in the oxide perovskites, wher...

Composition‐Controlled Synthesis of Hybrid Perovskite Nanoparticles by Ionic Metathesis: Bandgap Engineering Studies from Experiments and Theoretical Calculations

“…Ap lane-wave energy cut-off of 500 eV was used for all the calculations. [15] Although the study of MA + cation is out of the scope of the present study,o ur past studies [16] have revealed that in the tetragonal phase, the most stable structure is when the adjacent MA + cation are perpendicular to each other.T om ake the present study accurate, we have used the most symmetric MA + alignment (along the 100d irection) in the cubic phase and most stable perpendicular alignment of neighbouring CÀNdipoles in the tetragonal phase. The Brillouin zone sampling was done by using an automated G (gamma)-centred K-point mesh.…”

Advances in modelling and simulation of halide perovskites for solar cell applications

“…shorter wavelength light, with increasing mixing content. There exist other first-principles calculations of optical properties for CsSnI 3 [131], CsPbX 3 [132], MASnX 3 [133] and MABaI 3 [134].…”

Design of Lead-Free Inorganic Halide Perovskites for Solar Cells via Cation-Transmutation

“…[48][49][50][51][52] Alternatively, one can consider to transmute two divalent Pb 2+ ions into one monovalent ion M + and one trivalent ion M 3+ , i.e., 2Pb 2+ → M + + M 3+ , by keeping the total number of valance electrons unchanged at M IV sites. Known as atomic transmutation, this design strategy has led to great success in finding new materials with improved functionalities such as solar absorbers.…”