Rudorffites and Beyond: Perovskite‐Inspired Silver/Copper Pnictohalides for Next‐Generation Environmentally Friendly Photovoltaics and Optoelectronics

Abstract

In the wake of lead-halide perovskite research, bismuth-and antimony-based perovskite-inspired semiconducting materials are attracting increasing attention as safer and potentially more robust alternatives to lead-based archetypes. Of particular interest are the group IB-group VA halide compositions with a generic formula A x B y X x+3y (A + = Cu + /Ag + ; B 3+ = Bi 3+ /Sb 3+ ; X -= I -/Br -), i.e., silver/copper pnictohalides and derivatives thereof. This family of materials forms 3D structures with much higher solar cell efficiencies and greater potential for indoor photovoltaics than the lower-dimensional bismuth/ antimony-based perovskite-inspired semiconductors. Furthermore, silver/ copper pnictohalides are being investigated for applications beyond photovoltaics, e.g., for photodetection, ionization radiation detection, memristors, and chemical sensors. Such versatility parallels the wide range of possible compositions and synthetic routes, which enable various structural, morphological, and optoelectronic properties. This manuscript surveys the growing research on silver/copper pnictohalides, highlighting their composition-structure-property relationships and the status and prospects of the photovoltaic and optoelectronic devices based thereon. The authors hope that the insights provided herein might accelerate the development of eco-friendly and stable perovskiteinspired materials for next-generation photovoltaics and optoelectronics.

Perovskite-inspired Cu2AgBiI6 for mesoscopic indoor photovoltaics under realistic low-light intensity conditions

“…3,10 Amongst this broad family of lead-free compounds, 3,11,12 pnictohalide-based embodiments (i.e., compounds comprising Bi or Sb alongside halide anions) are typically air-stable due to the inherent stability of the pnictogen 3+ cations. [13][14][15][16] This property represents an added value for practical applications compared to the popular tin (Sn)-based halide perovskites, which, by contrast, suffer from the rapid oxidation of Sn 2+ . 17 Furthermore, the bandgaps of pnictohalidebased PIMs oen lie in the range of the optimum bandgap (1.9-2.0 eV) for IPVs, which could ultimately lead to a PCE(i) up to y60% in the radiative limit.…”

Critical Evaluation of the Photovoltaic Performance of (AgI)x(BiI3)y Thin Films from the Viewpoint of Ultrafast Spectroscopy and Photocurrent Experiments

“…Thin films composed of bismuth-based compounds have been actively explored over the last couple of years in this respect. 4−6 One important subgroup in this field is the silver iodobismuthates of the general formula (AgI) x (BiI 3 ) y (or equivalently Ag x Bi y I x+3y ), 7 which were also named rudorffites 8 on the basis of the structure of NaVO 2 reported by Rudorff. 9 The phase diagram of the silver iodobismuthate system is fairly complex.…”

“…Therefore, there is an ongoing quest for alternative lead-free photoabsorbers. Thin films composed of bismuth-based compounds have been actively explored over the last couple of years in this respect. − One important subgroup in this field is the silver iodobismuthates of the general formula (AgI) x (BiI 3 ) y (or equivalently Ag x Bi y I x +3 y ), which were also named rudorffites on the basis of the structure of NaVO 2 reported by Rüdorff . The phase diagram of the silver iodobismuthate system is fairly complex. , Several ternary Ag–Bi–I compounds have been identified, including AgBi 2 I 7 , AgBiI 4 , Ag 2 BiI 5 , and Ag 3 BiI 6 , which feature AgI/BiI 3 molar ratios of 1:2, 1:1, 2:1, and 3:1, respectively, and have a cubic close-packed iodide sublattice. , These compounds are also good silver ion conductors because of the cation vacancies in the crystal structure. , …”

A bismuth silver pnictohalide alternative to perovskite in fully-printable triple-mesoscopic solar cells

“…Silver pnictohalides (Ag-Bi-I) have attracted wide attention since 2016. [9][10][11] The controllable ratio of AgI to BiI 3 leads to varying compounds within this family, including AgBi 2 I 7 , AgBiI 4 , Ag 2 BiI 5 and Ag 3 BiI 6 , which have been extensively studied as light-absorbing materials. [9][10][11][12][13][14][15] The silver pnictohalide family shares similar 3D crystal structures and a suitable optical bandgap of 1.79-1.83 eV.…”

“…[9][10][11] The controllable ratio of AgI to BiI 3 leads to varying compounds within this family, including AgBi 2 I 7 , AgBiI 4 , Ag 2 BiI 5 and Ag 3 BiI 6 , which have been extensively studied as light-absorbing materials. [9][10][11][12][13][14][15] The silver pnictohalide family shares similar 3D crystal structures and a suitable optical bandgap of 1.79-1.83 eV. 10 According to the ratio of Ag and Bi, they are classied into two space groups: Fd 3m (AgBi 2 I 7 and AgBiI 4 ) and R 3m (Ag 2 BiI 5 and Ag 3 BiI 6 ).…”