High-Efficiency Green InP Quantum Dot-Based Electroluminescent Device Comprising Thick-Shell Quantum Dots

Indium phosphide (InP) core/shell quantum dots (QDs) without intrinsic toxicity have shown great potential to replace the widely applied cadmium-containing QDs in next-generation commercial display and lighting applications. However, it remains challenging to synthesize InP core/shell QDs with high quantum yields (QYs), uniform particle size, and simultaneously thicker shell thickness to reduce nonradiative Forster resonant energy transfer (FRET). Here, thick InP-Based QLEDs shell InP/GaP/ZnS//ZnS core/shell QDs with high stability, high QY (approximate to 70%), and large particle size (7.2 +/- 1.3 nm) are successfully synthesized through extending the growth time of shell materials along with the timely replenishment of shelling precursor. The existence of GaP interface layer minimizes the lattice mismatch and reduces interfacial defects. While thick ZnS shell, which suppresses the FRET between closely packed QDs, ensures high PL QY and stability. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on InP core/shell QDs with the peak external quantum efficiency and current efficiency of 6.3% and 13.7 cd A(-1), respectively, which are the most-efficient InP-based green quantum dot light-emitting diodes (QLEDs) till now. This work provides an effective strategy to further improve heavy-metal-free QLED performance and moves a significant step toward the commercial application of InP-based electroluminescent device.