Centimeter-Sized Na-Doped CsPb2Br5 Single Crystals with Efficient Self-Trapped Exciton Emission

We first report on the aqueous solution growth of centimeter-sized Na-doped CsPb2Br5 single crystals using a precursor solution with high NaBr concentration. The obtained Na-doped CsPb2Br5 single crystal has a tetragonal structure with a slight lattice contraction of 0.34% for Cs0.88Na0.12Pb2Br5. In comparison with the previously reported pure CsPb2Br5 single crystal, the Na-doped CsPb2Br5 single crystal shows interesting self-trapped exciton (STE) emission with emission peak at 689 nm, full width at half-maximum of 246 nm, and average photoluminescence lifetime of 429 ns. The STE emission feature of Na-doped CsPb2Br5 single crystal was further evidenced by the wavelength-dependent photoluminescence excitation spectra and intensity-dependent photoluminescence spectra measurements. By increasing the Na doping concentration, the photoluminescence quantum yields of Na-doped CsPb2Br5 single crystal can be greatly improved to a maximum value of 28.5% for Cs0.88Na0.12Pb2Br5. In addition, the methodology was also extended to fabricate Li-doped CsPb2Br5 single crystal with STE emission. The available Na-doped or Li-doped CsPb2Br5 single crystals are promising candidates for both fundamental research and the exploration of photonic applications.