Solution-Processed Bismuth Halide Perovskite Thin Films: Influence of Deposition Conditions and A-Site Alloying on Morphology and Optical Properties

Abstract

Bismuth-based halide perovskites have been proposed as a potential nontoxic alternative to lead halide perovskites; however, they have not realized suitable performance. Their poor performance has been attributed to substandard film morphologies and too wide of a band gap for many applications. Herein we used a two-step deposition procedure to convert BiI3 thin films into A3Bi2I9 (A = FA+, MA+, Cs+, or Rb+), which resulted in a substantial improvement in film morphology, a larger band gap, and greater compositional tunability compared toresults when using aconventional single-step deposition technique. Additionally, we attempted to reduce the undesirably wide band gap in Rb3Bi2I9 thin films by inducing chemical pressures through cation-size mismatch, with an underlying hypothesis that cation-size mismatch could induce compressive strain within the 2D Rb3Bi2I9 lattice. However, we found that all A x Rb3–x Bi2I9 compositions with x > 0 adopted the 0D structure, and no changes to the band gap were observed with alloy. These results imply that the band gap of A x Rb3–x Bi2I9 is insensitive to A-site alloying.

Single- or double A-site cations in A3Bi2I9 bismuth perovskites: What is the suitable choice?

“…This manifests that the A-site cation mixing in MA 3 Bi 2 I 9 with Cs influences the bandgap of bismuth perovskite-inspired materials. This observation is in contrast to the previously reported A x Rb 3−x Bi 2 I 9 perovskite-inspired materials in which the bandgap was insensitive to A-site cation engineering [45].…”

Lead‐Free Halide Perovskites for Light Emission: Recent Advances and Perspectives

“…In comparison with one‐step deposition, A 3 Bi 2 I 9 thin films synthesized by two‐step deposition are smoother and more homogeneous in grain size. [ 98 ]…”

Solvatochromic Photoluminescent Effects in All‐Inorganic Manganese(II)‐Based Perovskites by Highly Selective Solvent‐Induced Crystal‐to‐Crystal Phase Transformations

“…Tin‐based halide perovskite (ASnX 3 , A=Cs, MA, FA; X=Cl, Br, I) NCs were first considered as lead‐free perovskite materials due to the comparable ionic radius of Sn 2+ to Pb 2+ , which the lattice perturbation induced by substitution can be avoided [6, 10] . Antimony‐based and bismuth‐based perovskites can form 0D crystal structure A 3 B 2 X 9 (A=K, Rb, Cs, MA; B=Sb, Bi; X=Cl, Br, I) with great air stability [11–14] . The double‐perovskite structure Cs 2 B + B 3+ X 6 (B + =Ag + , Na + ; B 3+ =Bi 3+ , In 3+ , Sb 3+ ; X=Cl, Br, I) nanocrystals and single crystals have also been extensively explored from preparation method, quantum efficiency improvement, band gap regulation, theoretical calculation and other studies on photoelectric properties to applications in X‐ray or photoelectric detection [15–27] .…”