Facile synthesis of two-dimensional Ruddlesden–Popper perovskite quantum dots with fine-tunable optical properties

In hybrid organic-inorganic and all-inorganic metal halide perovskite nanomaterials, two-dimensional (2D) Ruddlesden-Popper (RP) perovskites have become one of the most interesting materials because of tunable bandgaps varied with the layer thickness, effective modulation of the electron-hole confinement, and high stability. Here, we report a one-pot synthesis of 2D RP perovskite (BA)₂(MA)_{n - 1}Pb_nX_{3n + 1} (BA = 1-butylammonium, MA = methylammonium, X = Br or I) quantum dots (QDs) with an average size of 10 nm at room temperature. The (BA)₂(MA)_{n - 1}Pb_nBr_{3n + 1} (Br series) QDs and (BA)₂(MA)_{n - 1}Pb_nI_{3n + 1} (I series) QDs exhibited tunable emitting spectrum in the range of 410-523 nm and 527-761 nm, respectively, with full width at half maximum (FWHM) of 12-75 nm. The emission color was tuned by the ratio of MA and halide. The photoluminescence quantum yield of 2D perovskite QDs reached 48.6% with more thermodynamic stability in comparison with 3D MAPbX₃ QDs. Overall results indicated that developing a solution synthesis for 2D RP perovskite QDs with great optical properties paves the way toward future optoelectronic devices and perovskite quantum dot photovoltaics.