Band-level control for high-performance colloidal quantum-dot LED

Here we report hybrid organic/inorganic quantum-dot LED with high-performance. Use of sol-gel TiO₂ as electron transport layer allows the device to be fabricated with all-solution process and have more efficient energy band structure for carrier injection and confinement. Quantum dot layer was crosslinked and thermally annealed to enhance the device performance. Quantum dot crosslinking not only made all-solution process feasible but also enhanced hole injection by shifting valance band of 0.3~0.6 eV, resulting in better charge balance. The degree of band-level shift depends on the asymmetric adsorption of ligand which might cause the dipole alignment of QD layer through the hole transport. The resulting device showed a high luminance (>;10,000 cd/m²), low turn on voltage (1.9 V), and the high power efficiency (2.41 lm/W). Incorporation of the technology into a display device with an active matrix drive backplane for the first time suggests that the approach is promising for high performance, easy-to-fabricate, large area displays and illumination sources.