Ligand size effects in two-dimensional hybrid copper halide perovskites crystals

Abstract

Intensive effort to tailor photophysics of lead-free perovskites is appealing in recent years. However, their combined electronic and optical property elucidations remain elusive. Here, we report spectroscopic observations of the coexistence Zhang-Rice singlet state and exotic electronic transitions in two-dimensional copper-based perovskites. Herein, several perovskites with different alkylammonium spacers are investigated to unravel their correlated electronic systems and optical responses. Namely, methylammonium, ethylammonium, phenylmethylammonium and phenethylammonium. Using temperature dependent high-resolution X-ray absorption spectroscopy, we observe distinct electronic features highlighting the impact of short spacer chains compared to long-conjugated ligands, demonstrating a pronounced 3d9 and 3d9L signature linewidth variation. Corroborated by density functional theory calculations, the transient dynamics evolution of copper-based hybrid perovskites is influenced by the strong interplay of electron-phonon interactions and geometric constrictions. This finding sheds light on tuning the electronic and optical properties of hybrid perovskites towards efficient photoactive-based devices.

BA2XBr4 (X = Pb, Cu, Sn): from lead to lead-free halide perovskite scintillators

“…Moreover, replacing the lead cation with other divalent cations may increase the Stokes shift of the materials. 7 An approach to replace lead with other metal cations has been attempted such as with manganese (Mn), 12 copper (Cu), 13 tin (Sn), 14 and antimony (Sb). 15 In this work, we aim to explore the effect of Pb substitution by Cu or Sn on the optical and scintillation properties of solution-processed 2D BA 2 PbBr 4 perovskite.…”

Emerging doping strategies in two-dimensional hybrid perovskite semiconductors for cutting edge optoelectronics applications

“…7(b) ). 107 This also revealed the arrangements of the spins of Cu within the CuCl 6 octahedron inducing local antiferromagnetic ordering at low temperature. Introduction of the FA cation in 2D DJ perovskites features a gradual bathochromic shift in the position of the emission signals with increasing number of layers ( n ).…”

“…7(b) ). 107 The Cu triplet state L 3 signal was found to be much more pronounced than that of the ground state d 9 L feature at 200 K, and d 9 L core holes were substantially increased with respect to the L 3 at high temperature due to the competing interactions between spin triplet and singlet states with the temperature ( Fig. 7(b) ).…”

“… 55 Very recently, Rusydi et al investigated the ligand size effects on the electronic transition across the unoccupied electronic state and emission properties of several Cu-based 2D perovskites ((MA) 2 CuCl 4 ) with different alkylammonium spacers, namely MA, EA, phenylmethylammonium (PMA), and PEA. 107 As the cation size increases, the Stokes shift becomes larger, suggesting a modulation of the activation energy barrier between free excitons and self-trapped exciton states. 107 By analyzing the temperature-dependent X-ray absorption spectra (XAS) systematically, they proposed that the additional –CH 2 moiety spans the organic ligand length inducing extra s states in the lead-free correlated hybrid perovskite electronic system; mixed covalent character can be moderately controlled by increasing the ligand size of the organic spacer and peculiar energetic transitions can be realized between the short versus long organic ligand spacer of the copper-hybrid perovskite ( Fig.…”

Hybrid Organic–Inorganic Perovskite Halide Materials for Photovoltaics towards Their Commercialization

“…The ideal t value for a stable perovskite would be 0.8 < t < 1.0, so the organic monocation value has to be adjusted to obtain the necessary t value [115]. However, the perovskite ligand size can have an influence on this value [116].…”