Hassan, N.Nagaraja, S.Saha, S.Tarafder, K.Ballav, N.2026-02-042024Chemical Science, 2024, 15, 11, pp. 4075-408520416520https://doi.org/10.1039/d3sc06255dhttps://idr.nitk.ac.in/handle/123456789/21279The everlasting pursuit of hybrid organic-inorganic lead-free semiconductors has directed the focus towards eco-friendly copper-based systems, perhaps because of the diversity in chemistry, controlling the structure-property relationship. In this work, we report single crystals of a Cu(i) halide-based perovskite-like organic-inorganic hybrid, (TMA)Cu<inf>2</inf>Br<inf>3</inf>, (TMA = tetramethylammonium), consisting of unusual one-dimensional inorganic anionic chains of -(Cu<inf>2</inf>Br<inf>3</inf>)-, electrostatically stabilized by organic cations, and the Cu(i)-Cu(i) distance of 2.775 Å indicates the possibility of cuprophilic interactions. X-ray photoelectron spectroscopy measurements further confirmed the presence of exclusive Cu(i) in (TMA)Cu<inf>2</inf>Br<inf>3</inf> and electronic structure calculations based on density functional theory suggested a direct bandgap value of 2.50 eV. The crystal device demonstrated an impressive bulk photovoltaic effect due to the emergence of excitonic Cu(i)-Cu(i) interactions, as was clearly visualized in the charge-density plot as well as in the Raman spectroscopic analysis. The single crystals of a silver analogue, (TMA)Ag<inf>2</inf>Br<inf>3</inf>, have also been synthesized revealing a Ag(i)-Ag(i) distance of 3.048 Å (signature of an argentophilic interaction). Unlike (TMA)Cu<inf>2</inf>Br<inf>3</inf>, where more density of states from Cu compared to Br near the Fermi level was observed, (TMA)Ag<inf>2</inf>Br<inf>3</inf> exhibited the opposite trend, possibly due to variation in the ionic potential influencing the overall bonding scenario. © 2024 The Royal Society of Chemistry.Chemical bondsCopper compoundsDensity functional theoryElectronic structureOrganic-inorganic materialsPerovskitePhotovoltaic effectsRaman spectroscopySilver compoundsSpectroscopic analysisX ray photoelectron spectroscopyCopper-basedEco-friendlyExcitonicsHybrid organic-inorganicLead-FreeOne-dimensionalOrganic-inorganic crystalsOrganic/Inorganic hybridsStructure-properties relationshipsTetramethylammoniumSingle crystals