Synthesis of centimeter-size two-dimensional hybrid perovskite single crystals with tunable, pure, and stable...

The environment-friendly synthesis and property modulation of two-dimensional organic-inorganic halide perovskite (2D OHP) single crystals with large sizes and high quality are important for the fabrication of optoelectric devices. In this work, plate-like and centimeter-size (BA)₂Pb(BrI_1-)₄ (BA = n-butylammonium, x: 0-1) single crystals with high crystallinity were synthesized via the cooling crystallization method in a mixed HX (X: I, Br) acid aqueous solution. The synthesized samples were single-phase with homogenously distributed Br and I ions. The lattice structure and bandgap of (BA)₂Pb(BrI_1-)₄ were both finely tuned through halide alloying. Pure photoluminescence with unitary wavelength was obtained in the mixed-halide samples compared to those of monohalides (BA)₂PbI₄ and (BA)₂PbBr₄. This is attributed to the structural homogeneity of the alloyed crystals. Moreover, the prepared (BA)₂Pb(BrI_1-)₄ samples showed higher photo and thermal stability for a long duration even with ion migration. This study will be an important reference for the fabrication and property modulation of 2D OHP-based light-emitting and other optoelectric devices.