Abstract
Developing of lead-free double perovskites have drawn significant interest for photovoltaics and optoelectronics as the materials have the potential to avoid toxicity and instability issues associated with lead-based organometallic perovskites. In this study, we report the optoelectronic properties of a new group of non-toxic lead-free organic-inorganic halide double perovskites composed of caesium (Cs), methylammonium (MA) or formamidinium (FA) with bismuth (Bi) and metal copper (Cu). We perform density functional theory investigations to calculate the structural, electronic and optical properties of 18 Pb-free compounds, ABiCuX6 [A = Cs2, (MA)2, (FA)2, CsMA, CsFA, MAFA; X = I, Br, Cl] to predict their suitability in photovoltaic and optoelectronic applications. We found that the considered compounds are semiconductors with a tunable band gap characteristics that are suitable for some devices like light emitting diodes. In addition to this, the high dielectric constant, high absorption, high optical conductivity and low reflectivity suggest that the materials have the potential in a wide range of optoelectronic applications including solar cells. Furthermore, we predict that the organic-inorganic hybrid double perovskite (FA)2BiCuI6 is the best candidate in photovoltaic and optoelectronic applications as the material has superior optical and electronic properties.
Highlights
Organic-inorganic hybrid perovskites having the general formula ABX31, where A is a relatively large inorganic or organic cation (e.g., Cs+ or CH3NH3+), B is a metal cation (e.g., Pb2+) and X is a halogen anion (e.g., I−, Br− or Cl−)[2], is an emerging class of materials which have attracted significant attention in recent years because of their extraordinary optoelectronic characteristics such as tunable electronic bandgap, high optical absorption with broad spectrum, good photoconductivity, low carrier effective masses with high mobility, extended charge diffusion lengths with high lifetimes[3,4,5,6,7,8,9]
A complex substitution of Pb has been addressed by a combination of a trivalent and monovalent cations to form a new structure known as double perovskites which can be represented by the general formula, A2B′B′′X6, where A is a relatively large cation, B′ and B′′ are either trivalent or monovalent cations, and X is either oxygen or halogen[2]
The structures of Cs-based inorganic double perovskites have been drawn, the structures are converted into 1 × 1 × 1 supercell to get the structures of organic-inorganic hybrid double perovskites
Summary
Organic-inorganic hybrid perovskites having the general formula ABX31, where A is a relatively large inorganic or organic cation (e.g., Cs+ or CH3NH3+), B is a metal cation (e.g., Pb2+) and X is a halogen anion (e.g., I−, Br− or Cl−)[2], is an emerging class of materials which have attracted significant attention in recent years because of their extraordinary optoelectronic characteristics such as tunable electronic bandgap, high optical absorption with broad spectrum, good photoconductivity, low carrier effective masses with high mobility, extended charge diffusion lengths with high lifetimes[3,4,5,6,7,8,9]. Been reported to have poor optoelectronic properties like high band gap, low absorption and large carrier effective masses, and poor photovoltaic performance[11]. Halide double perovskites have become more popular in the community of photovoltaic research because of its potential to overcome the instability and toxicity issues of Pb-based hybrid perovskites[2]. Electronic and optical properties of 18 organic-inorganic double perovskites ABiCuX6 [A = Cs2, (MA)[2], (FA)[2], CsMA, CsFA, MAFA; X = I, Br, Cl] by first-principles density functional theory (DFT) simulations to find effective replacements of Pb-based perovskites for photovoltaic and optoelectronic applications
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