Research on the electroluminescence of colloidal quantum dots is gathering momentum as the requirement for Rec 2020 (ITU-R-BT2020) cannot be achieved by means of state of art OLED materials (1-18). Quantum dots offer saturated colours, narrow emission and control over the emitted wavelength by varying the quantum dot size and composition. OLEDs have high efficiency and long lifetime and thus they have been accepted into the mainstream products such as mobile phones and curved TV. However, while efficiency of green QLEDs have exceeded that of PHOLEDs, the red and the blue QLEDs are yet to achieve sufficiently high efficiencies. The life-times of QLEDs are not yet long enough for commercial acceptance. The question is whether quantum dots would be good enough to yield colour co-ordinates satisfying the REC 2020 specification. This paper reports our successful effort to achieve the REC 2020 colour co-ordinates for red with world record efficiency and long life time to be a serious contender for the Red Pholeds. To the best of our knowledge, this is the first report of achieving the REC colour co-ordinate of (0.708, 0.292) and indeed exceeding to (0.712, 0.288) indicating that it is also possible to achieve REC 2020 green and blue colour co-ordinates if suitable QDs are developed and appropriate device architecture built.
The paper will review the various electroluminescent display and lighting technologies based OLEDs (Small Molecules) , POLEDs (Polymer OLEDs), QLEDs, Perovskite OLEDs and rare earth chelate based OLEDs.
This paper reports our attempt to match the REC 2020 colour co-ordinates with red CdSe/ZnS (0.708, 0.292) , red CFQD® and green CFQD®. We report here red quantum dot based electroluminescent devices (QLEDs) that meet the colour co-ordinates requirement set by REC2020. We also report the world first dark red CFQD® (heavy metal free) ((x,y), (0.696, 0.303)) devices. The electroluminescent characteristics of devices of both CdSe/ZnS and cadmium free quantum dots are compared. The conduction mechanism and life-time of these devices will also presented.