Enhanced visible light absorption in layered Cs₃Bi₂Br₉ through mixed-valence Sn(ii)/Sn(iv) doping

Abstract

Lead-free halides with perovskite-related structures, such as the vacancy-ordered perovskite Cs3Bi2Br9,are of interest for photovoltaic and optoelectronic applications. We find that addition of SnBr2 to the solution-phase synthesis of...

Structure modulation for bandgap engineered vacancy-ordered Cs3Bi2Br9 perovskite structures through copper alloying

“…3d). Krajewska et al previously observed color conversion during grinding of Sn-doped Cs 3 Bi 2 Br 9 perovskite crystals, 31 in which the black color of Sn-doped Cs 3 Bi 2 Br 9 crystals transformed to a yellow color. Their attribution of the color conversion to the oxidation of the Sn 2+ during the grinding into Sn 4+ could not be matched with findings of Cu-alloyed perovskites, where, unlike Sn 2+ , Cu 2+ does not have an oxidative route.…”

“…Moreover, the presence of mixed-valence cations through the perovskite structure promotes the intervalence charge transfer, as discussed in the literature. 31,51 This might explain the lower bandgap of the alloyed matrix compared to the pristine Cs 3 Bi 2 Br 9 perovskite. The XPS spectra of other elements are illustrated in the ESI, † Fig.…”

“…24 Recently, a drastic redshift in the optical properties of Cs 3 Bi 2 Br 9 was obtained by substitution of Bi 3+ with mixed-valence (Sn 2+ /Sn 4+ ) and the resulting perovskite exhibited strong intervalence charge transfer (IVCT). 31 Because of their high moisture stability and strong light absorption, lead-free copper (Cu)-based perovskites have piqued the interest of researchers. Vargas et al reported 2D double perovskite Cs 4 CuSb 2 Cl 12 with a reduced bandgap of 1 eV due to the presence of an unpaired electron in 3d 9 -configurated Cu 2+ where overlapping of Cu-3d orbitals with Cl and Sb orbitals leads to valence band broadening and bandgap narrowing.…”

Mixed valence Sn doped (CH3NH3)3Bi2Br9 produced by mechanochemical synthesis

“…23 We have recently shown that Cs3Bi2Br9 can be doped with mixed valence Sn through a solution phase synthesis. 24 Here we show that a related hybrid material, MA3Bi2Br9 (MA = (CH3NH3) + ) can similarly be doped with mixed valence Sn(II) / Sn(IV) by a very rapid room temperature, solvent free mechanochemical reaction carried out in air. Mechanochemical reactions have been used as a synthesis strategy for a long time in many areas such as to prepare polymeric materials, 25 metal organic frameworks (MOFs) 26,27 and halide perovskites.…”

Impact of metastable defect structures on carrier recombination in solar cells

“…1,10 Point defects can exhibit complex potential energy surfaces (PESs), with multiple local minima. 9,[11][12][13][14] As such, their atomic structures often do not reside solely in their global equilibrium configuration, but may access alternative metastable structures via thermal, photo or electronic conversion. The possibility of structural transformation at defect sites has several potential impacts for technological applications -for example, low energy barriers between structures could lead to coherence corruption and a breakdown in performance for defects used in quantum computing and single-photon emission.…”