Enabling Narrow Emission Line Widths in Colloidal Nanocrystals through Coalescence Growth

With continuing progress in the chemical synthesis of colloidal semiconductor nanocrystals (NC), one property that remains elusive to the rational design is the ensemble photoluminescence (PL) line width. Given the growing demand for NC-based light-emitting materials, substantial research effort has been dedicated to this issue. Here, we demonstrate a postsynthetic strategy that allows reducing emission line widths of CdSe and CdS NCs to near single-particle levels while enhancing the PL quantum yield. The key idea behind the synthetic approach lies in employing a nonclassical coalescence growth mechanism, which leads to size focusing irrespective of the initial sample morphology. Numerical simulations accurately predict the observed particle size evolution, confirming the ability of coalescence growth to promote size focusing of semiconductor colloids. Ultimately, we expect that the demonstrated coalescence growth strategy could enable a rational control of nanocrystal size distributions and corresponding spectral line widths in many types of semiconductor NCs.