Figure 1: Comparisons between conventional size-tuned QDs (top) and brightness-equalized QDs (bottom).

(a) Schematic depictions of ST-QD structures show that emission wavelength and extinction coefficient are largely dictated by the CdSe core size, and that the shell, composed of CdS, ZnS or alloys of the two, controls the quantum yield. (b) Extinction coefficient spectra of ST-QDs show a wide disparity in light absorption per-particle, resulting in (c) dissimilar fluorescence brightness values when excited at the same wavelength (here 400 nm). (d) Schematic depiction of BE-QD structures for which the core size is fixed and wavelength is tuned through the bandgap of composition-tunable alloys. The shell comprises two spherically concentric domains: the CdS shell is used to precisely match the extinction coefficients and the ZnS shell is used to equalize the quantum yields. (e) Extinction coefficient spectra of BE-QDs show convergence below 450 nm, resulting in (f) equalized fluorescence brightness when excited at the same wavelength (400 nm). Graphs depict representative experimental data plotted with wavelength axes scaled in proportion to energy.