Bandgap lowering in mixed alloys of Cs₂Ag(Sb_xBi_1−x)Br₆ double perovskite thin films

Abstract

Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air and long charge-carrier lifetimes. However, most double perovskites, including Cs2AgBiBr6, have wide bandgaps,...

Efficient Emission in Halide Layered Double Perovskites: The Role of Sb3+ Substitution in Cs4Cd1–xMnxBi2Cl12 Phosphors

“…42 For Cs2Ag(SbxBi1-x)Br6 alloys, Z. Li and collaborators proposed a bowing originating from a type II gap alignment between the pure compounds, which allows the non-linear mixing of electronic states. 46 A similar effect could be taking place in the Bi/Sb solid solutions (Figure 5). Importantly, the band edge absorption shift has a clear effect on the PL intensity; as it shifts to shorter wavelengths, the emission intensity increases (Figure S6).…”

“…15 Furthermore, in some Bi materials, the relativistic contraction of the 6s orbital results in a more localized, lower-energy valence s orbital, compared to Sb 5s lone pair. 45,46,48 This is further supported by the fact that the Sb-materials band edge absorption is redshifted in comparison to the Bi-materials, which is an exception to the typical trend of decreasing bandgap upon atomic substitution with heavier members from the same periodic group. 46 Hoye and collaborators observed the same effect in Cs2Ag(SbxBi1-x)Br6 alloys, which was attributed to a stronger interaction of the Sb 5s 2 lone pair with Ag and Br orbitals.…”

“…45,46,48 This is further supported by the fact that the Sb-materials band edge absorption is redshifted in comparison to the Bi-materials, which is an exception to the typical trend of decreasing bandgap upon atomic substitution with heavier members from the same periodic group. 46 Hoye and collaborators observed the same effect in Cs2Ag(SbxBi1-x)Br6 alloys, which was attributed to a stronger interaction of the Sb 5s 2 lone pair with Ag and Br orbitals. In our case, the band gap contraction could be due to a slight better coupling of the Sb lone pair with the Cl p and Cd orbitals that constitute both the CB and VB, slightly increasing delocalization but decreasing the radiative recombination on Mn 2+ sites.…”

The Bottlenecks of Cs2AgBiBr6 Solar Cells: How Contacts and Slow Transients Limit the Performance

“…[ 19,21 ] Although first solar cell reports were published several years ago with an initial PCE of ≈2.5%, [ 22 ] researchers so far have struggled to achieve a PCE exceeding 2.84% by using this material as absorber. [ 20,23–30 ] Besides addressing the possibility to tune the rather large and indirect bandgap and more generally the absorption onset using additives and alloying, [ 31–35 ] several studies have focused on the identification of the limiting factors hampering the performance of this material in order to overcome these issues and to push the PCE of the solar cells toward the theoretical limit. Kentsch et al.…”

“…[19,21] Although first solar cell reports were published several years ago with an initial PCE of ≈2.5%, [22] researchers so far have struggled to achieve a PCE exceeding 2.84% by using this material as absorber. [20,[23][24][25][26][27][28][29][30] Besides addressing the possibility to tune the rather large and indirect bandgap and more generally the absorption onset using additives and alloying, [31][32][33][34][35] several studies have focused on the identification of the limiting Cs 2 AgBiBr 6 has attracted much interest as a potential lead-free alternative for perovskite solar cells. Although this material offers encouraging optoelectronic features, severe bottlenecks limit the performance of the resulting solar cells to a power conversion efficiency of below 3%.…”