Halide Pb-Free Double–Perovskites: Ternary vs. Quaternary Stoichiometry

Abstract

<jats:p>In view of their applicability in optoelectronics, we review here the relevant structural, electronic, and optical features of the inorganic Pb-free halide perovskite class. In particular, after discussing the reasons that have motivated their introduction in opposition to their more widely investigated organic-inorganic counterparts, we highlight milestones already achieved in their synthesis and characterization and show how the use of ab initio ground and excited state methods is relevant in predicting their properties and in disclosing yet unsolved issues which characterize both ternary and quaternary stoichiometry double-perovskites.</jats:p>

Preserving Bond Ionicity under Illumination to Achieve Photostable Halide Perovskites

“…Smaller values (t < 0.89) lead to crystallization into orthorhombic perovskite structures, while larger values (t > 1) enable formation of hexagonal and quasi-2D structures. 30 For the PbI 3 inorganic frame in bulk crystals, the Goldschmidt formula is fulfilled by A cations larger than Cs (with t = 0.8) and smaller than FA (with t = 0.99). Undersized A cations such as Rb and K and oversized cations such as guanidinium (C(NH 2 ) 3 PbI 3 , or GU) 31 serve as dopands for the calibration of t. Often, the X 1− site is codoped with other halides.…”

“…For a cubic perovskite structure, the t factor is usually between 0.9 and 1. Smaller values ( t < 0.89) lead to crystallization into orthorhombic perovskite structures, while larger values ( t > 1) enable formation of hexagonal and quasi-2D structures . For the PbI 3 inorganic frame in bulk crystals, the Goldschmidt formula is fulfilled by A cations larger than Cs (with t = 0.8) and smaller than FA (with t = 0.99).…”

Spray‐Coated Lead‐Free Cs2AgBiBr6 Double Perovskite Solar Cells with High Open‐Circuit Voltage

“…[7,8] This is why many research groups focus-through theoretical and/or experimental studies-on the development of lead-free perovskite materials. [9][10][11][12][13][14][15] To diminish the amount of lead in perovskite PV absorber, two options are generally envisaged: the first is to replace a fraction of lead by a non-hazardous metal cation; the second is to completely substitute lead by a nontoxic element such as Ge(II), Mn(II), Cu(II), Bi(III), or Sb(III). [10] Lead-free halide double perovskites are considered as one of the promising PV absorber alternatives to lead halide perovskite in view of their nontoxic character and long-term stability.…”

Exploration of New Double Peroviskites Cs2YInX6 (X = Cl, Br, I) for Opto-Electronic and Sustainable Energy Applications

“…Reported literature shows that bandgap values with SOC are closely related to experimental values. 26,27 Therefore, we also employ mBJ potential with SOC for the investigations of bandgap for Cs 2 YInX 6 (X = Cl, Br, I) double perovskites (see Fig. 2) for the first time and their calculated direct bandgap Eg (Γ-Γ) values with and without SOC are listed in Table II.…”