Figure 3: QD extinction coefficient equalization through CdS shell growth.
The left two columns depict a representative equalization process for two CdSe cores with different sizes (2.0 and 4.3 nm) and the right two columns depict a representative equalization process for two alloy cores (HgxCd1-xSeyS1-y) with different compositions but similar sizes. (a–d) Extinction coefficient spectra are depicted for the four cores during capping with CdS in deposition increments of 0.8 monolayers; extinction increases with increasing shell thickness. Spectra depict the first 5–7 increments. (e,g) The trends in extinction coefficient values at 400 nm with different CdS shell thicknesses. Dashed lines are extinction isolines, connection points of equal extinction. (f,h) Spectra of two colours of QDs with matched extinction, showing strong correlation between 350 and 450 nm. Insets show ratios of spectra for each of these extinction-matched pairs. (i,j) The wavelength tunability of the resulting QDs, with substantially wider spectral range provided with alloy cores. Four example QD colours are shown in j.
