Fig. 4: sg-QDs with variable PL energies and their photonic application.

a Single exciton PL spectra of individual sg-CdSe (r, nm)-ZnSe (H = 5.0 nm) and Cd_0.25Zn_0.75Se (r, nm)-ZnSe (H = 5.0 nm) QDs with varying core radii. Each spectrum is fitted with double Lorentzian curves to decouple 1S_HX,em (light shaded) and 1S_LX,em (dark shaded). The inset is a photographic image of CdSe-ZnSe and Cd_0.25Zn_0.75Se-ZnSe sg-QD solutions with variable PL energies. b Absolute PL QYs of CdSe-ZnSe sg-QDs with varying core radii (1.4 nm ≤ r ≤ 4.5 nm) and Cd_0.25Zn_0.75Se-ZnSe sg-QDs with varying core radii (1.8 nm ≤ r ≤ 2.4 nm) at a fixed shell dimension (H = 5.0 nm). The inset in (b) shows CIE color coordinates of the series of sg-QDs. c Statistics showing PL linewidths and peak PL energies of individual CdSe-ZnSe sg-QDs (r = 4.0, 3.0, 2.0 and 1.4 nm, respectively) and Cd_0.25Zn_0.75Se-ZnSe sg-QDs (r = 1.8 nm) at a fixed shell dimension (H = 5.0 nm) (more than 25 dots per each sample). Symbols are averages and error bars are standard deviations. d–f Rotation angle dependent DOP of 1S_HX,em and 1S_LX,em for (d), red, (e), green and (f), blue emitting sg-QDs. g Schematic illustrations of QD-LED (top) and its energy band diagram (bottom). h EL spectrum, (i) current density-voltage-luminance characteristics, and (j) external quantum efficiencies (EQEs) versus luminance curve of the QD-LED (inset: a photograph of the working device, scale bar is 10 mm).