Fig. 1: Optical characterizations.
From: Robust excitonic light emission in 2D tin halide perovskites by weak excited state polaronic effect
a Schematic of (PEA)2(MA)Sn2I7 and optical image of BN-encapsulated (PEA)2(MA)Sn2I7 thin flake (~20 layers). Scale bar: 10 μm. Inset: optical image of (PEA)2(MA)Sn2I7 single crystal. b The absorption and photoluminescence (PL) spectra of (PEA)2(MA)Sn2I7 and (PEA)2(MA)Pb2I7 flakes at room temperature. c The 1st derivative spectra of the reflectance contrast of (PEA)2(MA)Sn2I7 and (PEA)2(MA)Pb2I7 at 4 K. The 1s and 2s exciton states are denoted.
