The so-called 329 perovskites, with their A3B2X9 stoichiometry, are attracting broad interest for their lead-free nature, environmental stability, and potential in optoelectronic devices such as solar cells and light emitters....our latest publication in @J_A_C_S: "Ultrafast Carrier Self-Trapping Driven by Strong Exciton–Phonon Coupling in 2D MA3Bi2I6Cl3 Perovskite." In this work, we explore lead-free 2D hybrid bismuth halide perovskites for optoelectronic applications. Using temperature-dependent photoluminescence and femtosecond transient absorption spectroscopy, we uncover strong exciton-phonon interactions, characterized by giant Huang-Rhys factors, coherent phonon oscillations, and ultrafast carrier self-trapping into small-polaron and self-trapped exciton (STE) states. Photoexcited carriers rapidly localize, with PL emission primarily from STEs, while free exciton emission is minimal and transient. Comparisons with 0D MA3Bi2I9 and 2D MA3Bi2Br9 highlight how halide composition and dimensionality modulate free excitons versus localization. Read more: pubs.acs.org/doi/abs/10.1021… #Perovskites #LeadFreeMaterials #Optoelectronics #MaterialsScience #Nanotech

In JACS: Deterministic control of the long debated Sn3+ state in AgSnSe2, one of chemistry’s “impossible” oxidation states. Using XPS, Mössbauer, and XAS (backed by DFT), we directly confirm uniform Sn3+ in pristine AgSnSe2. Sb substitution provides a clean chemical knob that drives Sn from +3 to mixed +2/+4 (valence skipping), progressively suppressing superconductivity (Tc ~5 K) and inducing a metal-to-semiconductor transition. A rare system to interrogate how valence reshapes the electronic ground state. DOI: 10.1021/jacs.5c21696

Through Interdisciplinary Work at Northwestern, Advanced Imaging Reveals Hidden Thermoelectric Structure mccormick.northwestern.edu/n…