Surface Ligand Engineering to Modulate the Synthesis of DJ-Type 2D Sn-Based Perovskites for Light-Emitting Diodes

The advancement of novel lead-free and stable metal halide perovskites is crucial in addressing the environmental risks associated with lead-based perovskites and broadening their range of applications. Two-dimensional (2D) Sn-based perovskites have been increasingly recognized for their outstanding optoelectronic properties and notable stability. In this study, we have successfully synthesized three variants of Dion-Jacobson (DJ)-type 2D Sn-based perovskites (H3NCnH2nNH3)SnBr4 through surface ligand modification using 1,6-diaminohexane (C6), 1,8-octanediamine (C8), and 1,10-decanediamine (C10). C6SnBr(4) exhibits an exceptionally high absolute photoluminescence quantum yield (PLQY) of up to 95%. Analysis of low-temperature PL spectra sheds light on the luminescence mechanism of C6SnBr(4), emphasizing the interaction between band-edge emission and self-trapped state emission. Density functional theory (DFT) calculations reveal a bandgap (E-g) of 2.07 eV for C6SnBr(4), consistent with experimental findings. Furthermore, the monochromatic phosphor-converted light-emitting diode (LED) incorporating C6SnBr(4) displays a correlated color temperature (CCT) of 2483 K, emitting a vibrant yellow-orange hue with a color rendering index (R-a) of 47.7, and CIE color coordinates of (0.514, 0.471). These findings offer valuable insights for enhancing the absolute PLQY and stability of DJ-type 2D Sn-based perovskites.