At 260 C, 0.2 and 0.5 equivalents of Cd (with respect to the amount of In or Cu as starting materials) were alloyed into CIS NCs. As shown in Fig. 2a, peak QYs are increased to *14 % which are about double those compared to CIS NCs (*7 %). The enhancement of the peak QY suggests that Cd minimizes NC intrinsic or surface defects. It also can be seen that
without Cd, the system reacts for 15 min before product precipitation. However, with Cd the system reaction time is prolonged. During elongated reaction times, NC peak wavelengths shift toward infrared wavelengths, indicating further size growth of NCs. Higher concentrations of Cd in the reaction cause greater red-shift along with a longer reaction time. It is believed that Cd has stronger coordination properties with DDT. If more Cd atoms are exposed at Cd–CIS NC surfaces, they may facilitate colloidal stability and further NC growth. In addition, Fig. 2a showsminimal gaps among curves of peak PL wavelengths. This suggests that Cd composition percentage does not significantly change the NC bandgap but does impact NC size growth for the further bandgap tuning.