Blue-Emitting Colloidal In1– x Ga x P Quantum Dots Synthesized in Molten Salt: Toward Blue QLEDs with Improved Stability
Aritrajit Gupta, Yi-Chen Chen, Justin C. Ondry, Danial Zangeneh, Yuan Liu, Hogeun Chang, Ji Hyun Min, Jae-Yong Lee, Da-Eun Yoon, Jiayang Zhou, Kailai Lin, Jun Hyuk Chang, Eran Rabani, Robert F. Klie, Richard D. Schaller, Dmitri V. TalapinAbstract
Colloidal quantum dots (QDs) are being actively explored for QD light-emitting diode (QD-LED) displays with high color purity and wide color gamut, high brightness, and low-cost, solution-based manufacturing. Heavy metal-free InP QDs have enabled red- and green-emitting QD LEDs with excellent device characteristics. However, the performance of blue QD-LEDs, required for completing the red, green, and blue (RGB) full color gamut, is lagging behind, which prompts searches for novel blue-emitting QDs. Here, we report the synthesis, computational modeling, and structural and spectroscopic studies of heavy metal-free blue-emitting core-shell QDs featuring 2.1 nm In1–xGaxP cores, colloidally synthesized in a molten inorganic salt, epitaxially coated with ZnS shells, and optimized surface treatments. The computational study suggests that the introduction of a ZnS shell induces mixing between core and shell electronic states, enhancing the direct-gap character of In1–xGaxP/ZnS QDs. The resulting In1–xGaxP/ZnS QDs show blue band-edge photo- and electroluminescence that can be fine-tuned around the technologically important region of 470 nm. This material holds strong promise for filling the blue gap in full-gamut QD-LED displays.