From Pb to Bi: A Promising Family of Pb‐Free Optoelectronic Materials and Devices

Abstract

Lead‐based organic–inorganic hybrid perovskite materials are widely used in optoelectronic devices due to their excellent photophysical properties. However, the main issues which hinder its commercialization are the toxicity caused by lead and the intrinsic instability of the material. Recently, many lead‐free halide materials with good intrinsic stability have been reported, among which bismuth‐based halide materials have attracted extensive research due to their structure and promising optoelectronic properties. In this review, bismuth‐based materials are divided into binary BiX3 (X = I, Br, Cl), ternary AaBibXa+3b (A = Cs, Rb, MA, Ag, etc.), and quaternary A2AgBiX6 (A = Cs, Rb, MA, etc.) according to its elemental composition. The structure and optoelectronic properties of bismuth‐based halide materials, which may be helpful for the development of bismuth‐based halide materials and lead‐free perovskites in the future, are summarized and highlighted.

Reducing current fluctuation of Cs3Bi2Br9 perovskite photodetectors for diffuse reflection imaging with wide dynamic range

“…Although tin (Sn) or germanium (Ge) based perovskites have been discussed in previous reports because the metal Sn or Ge shares a similar diameter and electron structure to Pb, they usually exhibit poor stability mainly because divalent ions (Sn 2+ and Ge 2+ ) are readily oxidized to tetravalent ions (Sn 4+ and Ge 4+ ) in the oxygen and water contained environment [14,15]. Alternatively, bismuth (Bi)-based perovskites have been found possessing long-term stability and featuring excellent photosensitivity, so they have obtained more attention from the researchers, and are regarded as promising lead-free perovskite materials [16]. Researchers have fabricated various stable Bibased perovskite thin films including Cs 3 BiBr 6 , CsBi 3 I 10 , Cs 3 Bi 2 Br 9 , Cs 2 AgBiBr 6 and Cs 3 Bi 2 I 9 [17][18][19][20][21][22].…”

Rigid Amine‐Induced Pseudo‐3 D Lead‐Free Bismuth Halide Perovskite with an Improved Band Edge for Visible‐Light Absorption

“…The band gap of the MA 3 Bi 2 I 9 film (2.1 eV) was similar to that of Cs 3 Bi 2 I 9 (2.2 eV) . Recently, band gap engineering has focused on fabricating Bi‐based materials based on these two kind of perovskites, including the synthesis of double perovskites such as Cs 2 AgBiI 6 , (MA) 2 AgBiI 6 , and (MA) 2 TlBiBr 6 . Vigneshwaran and co‐workers first obtained a novel sulfur‐doped MA 3 Bi 2 I 9 film with a reduced band gap of 1.45 eV .…”

“…Various studies have focused on replacing Pb in organometal halide perovskites by using less toxic metal cations, including Sn, In, Sb, and Bi . In recent years, Bi, as a neighbor of Pb in the periodic table, has attracted considerable attention as a candidate element for the preparation of Pb‐free perovskites . Bi has been demonstrated to be a harmless and chemically stable element, which has sparked interest in areas from medicinal to industrial chemistry .…”

“…Owing to the difference in valence states between lead(II) and bismuth(III), Bi‐based perovskites cannot be constructed by simply replacing lead(II) with bismuth(III). Therefore, cations are expected to form various vacancy‐ordered perovskites A a Bi b X a +3 b , according to the principle of charge conservation; A is a monocation that balances the structural charges, such as Cs or CH 3 NH 3 (MA), and a is the amount of required charge. Recently, significant efforts have been devoted to comprehensively understanding the optoelectronic properties of typical Bi‐based materials, A 3 Bi 2 X 9 (A=Cs, MA), by fabricating high‐quality single crystals or films, even though their crystal structures have been studied in the last century .…”

In Situ Construction of Lead‐Free Perovskite Direct Z‐Scheme Heterojunction Cs3Bi2I9/Bi2WO6 for Efficient Photocatalysis of CO2 Reduction

“…In particular, all‐inorganic cesium bismuth halide (Cs 3 Bi 2 X 9 , X = Br or I) perovskite nanocrystals have been actively exploited as photocatalysts for CO 2 reduction, [ 28 ] H 2 evolution, [ 32 ] organic synthesis, [ 25 ] and organic pollutant degradation. [ 33 ] One fly in the ointment is that Cs 3 Bi 2 X 9 has a higher exciton binding energy [ 35 ] and more deep energy defects [ 36 ] with respect to LHP, which is unfavorable for the charge separation, [ 37 ] and, thus, limits the enhancement of photocatalytic performance. Therefore, it is highly anticipated to develop appropriate strategies to improve the charge separation efficiency of lead‐free perovskite.…”