Ethanol-assisted synthesis of two-dimensional tin(ii) halide perovskite single crystals for amplified spontaneous emission

Abstract

Two-dimensional (2D) Ruddlesden–Popper perovskites (RPPs) are emerging as star materials for their superior optoelectronic properties. In particular, lead-free tin(II)-based 2D RPPs have recently gained more attention. However, until now, 2D tin(II)-based perovskite lasing has not been achieved. High-quality single crystals (SCs) with a low trap density are a good gain medium candidate for lasing. Unfortunately, research on the controllable synthesis of tin(II)-based SCs is still very limited. In this work, we developed a novel synthesis strategy in which ethanol was introduced to control the solubility of the perovskite precursors. We prepared high-quality RPP (TEA)₂(MA)_n−1Sn_nI_3n+1 (n = 1 or n = 2, TEA = 2-thiopheneethylamine, MA = methylamine) SCs, and investigated their structural and optical properties. The exciton binding energy of tin(II)-based 2D perovskites was fitted to 184.1 meV and 46.13 meV for (TEA)₂SnI₄ (n = 1) and (TEA)₂(MA)Sn₂I₇ (n = 2) SCs, respectively, which is much higher than for polycrystalline thin films. We further investigated the optical gain behavior of the tin(II)-based 2D perovskites. The amplified spontaneous emission (ASE) of exfoliated SCs was demonstrated at 20 K with a threshold of 29.1 μJ cm⁻² for (TEA)₂SnI₄ (n = 1) and 630.1 μJ cm⁻² for (TEA)₂(MA)Sn₂I₇ (n = 2).