Ambient-stable near Unity Photoluminescence Quantum Yield in Two-dimensional Tin Bromide Perovskites

Abstract

Semiconductor nanostructures with near-unity photoluminescence quantum yields (PLQYs) are imperative for light-emitting diodes and display devices.With 1,8 diaminooctane (8N8) interlayer spacer, the Dion-Jacobson (8N8)SnBr4 (8N8-DJ) perovskite demonstrates a PLQY of 99.7±0.3%. The near-unity PLQY of 8N8-DJ has outstanding ambient stability for over a month throughout the entire excitation wavelength range. By changing the spacer to n-octylamine (8N), Ruddlesden-Popper (8N)2SnBr4 (8N-RP) also has an appreciable PLQY of 91.7±0.6%. However, the PLQY of 8N-RP is unstable under ambient conditions due to increased lattice strain and structural degradation of the perovskite phase. The PL experiments from 5K to 300K decipher the room temperature PLQY to be due to the self-trapped emission (STE) where the self-trapping depth is 25.6±0.4 meV below the conduction band as a result of strong carrier-phonon coupling. With 34.7-37.3meV exciton binding energy, the ~5.5 s long-lived STE emission dominates over the band edge (BE) peaks at lower excitation wavelengths and higher temperatures. The higher PLQY and stability of 8N8-DJ are due to the stronger interaction between SnBr64- octahedra and 1,8 diammonium octane cation leading to a more rigid structure. The near-unity PLQY of 8N8-DJ remains unchanged from its powder form to the polymer-embedded perovskite films with varying thicknesses.

Utilizing the Undesirable Oxidation of Lead-Free Hybrid Halide Perovskite Nanosheets for Solar-Driven Photocatalytic C(sp3)─H Activation: Unraveling the Serendipity

“…Nevertheless, the presence of oxygen in MA 2 SnBr 6 is attributed to the formation of SnO 2 (Figure S7a), which was also confirmed by the PXRD pattern of MA 2 SnBr 6 . The high-resolution XPS (HR-XPS) of the Sn 3d fitted curve of as-synthesized MASnBr 3 shows peaks at binding energies 486.7 and 495.1 eV, which correspond to Sn 2+ (Figure a), while for MA 2 SnBr 6 , peaks at 487.4 and 495.8 eV correspond to the Sn 4+ state (Figure a). , Thereafter, the Sn 3d curves of MASnBr 3 were compared with samples aged for 4, 8, and 10 days, in which a 0.7 eV peak shift in binding energy was observed (Figure S7b). With respect to the above observations, Sn 3d curves of 2, 4, 6, and 8 days of oxidized samples were deconvoluted into two peaks representing Sn 2+ and Sn 4+ binding energies, and the ratio of Sn 2+ and Sn 4+ in the oxidized samples was calculated (Figure b and Table S2).…”