Toward Engineering Intrinsic Line Widths and Line Broadening in Perovskite Nanoplatelets

Perovskite nanoplatelets possess extremely narrow absorption and emission line widths, which are crucial characteristics for many optical applications. However, their underlying intrinsic extrinsic line-broadening mechanisms poorly understood. Here, we apply multidimensional coherent spectroscopy to determine the homogeneous broadening of colloidal perovskite nanoplatelet ensembles. We demonstrate a dependence not only widths but also various on platelet geometry. find that decreasing thickness by single monolayer results in 2-fold reduction inhomogeneous width 3-fold sub-millielectronvolts regime. In addition, our measurements suggest homogeneously broadened exciton resonances two-layer (but necessarily three-layer) at room-temperature.