Fig.3

Biexciton emission properties of Spheroid 3 (First row: ensemble; Second row: single particle). a Excitation-fluence dependent PL decay curves of a typical ensemble sample measured using a micro-liquid film method. b The PL recombination dynamics of biexcitons (solid lines) that extracted by subtracting the single-exciton component. They are fitted using mono-exponential decay functions (dotted lines), yielding the biexciton lifetime \({\tau }_{\mathrm{xx}}\approx 6.3\) ns. The inset shows excitation-fluence dependent single-exciton (black dots) and faster component (purple dots) PL intensity extracted from (a). The excitation-fluence dependence of faster component PL intensity follows quadratic scaling (purple dotted line) of biexcitons. c Excitation-fluence dependent single-exciton (black dots) and total PL intensities (red dots) of ensemble sample. Solid lines are the fits to the emission saturation model for single-exciton PL (black) and total PL (red), respectively, yielding QY_xx of ~ 78%. d Representative blinking traces and corresponding distribution of intensities for single particle sample. Red line was chosen as the threshold between “on” and “off” states. e Typical second-order photon correlation curve from single particle sample. The calculated QY_xx is ~ 80%