Partially pyridine-functionalized quantum dots for efficient red, green, and blue light-emitting diodes

Surface-exchanged, partially pyridine-functionalized colloidal quantum dot-based light-emitting diodes (QD-LEDs) that exhibit a low turn-on voltage and high brightness are reported. Pyridine is stochastically exchanged to a greater extent at the interface between the QDs and the hole transport layer via ligand exchange. Pyridine improves the charge balance within the QDs by enhancing the hole injection and hence lowers the turn-on voltage of the QD-LEDs. This strategy is applied to red-, green-, and blue-emitting (three primary colors) QD-LEDs. Pyridine-functionalized QD-LEDs (QD/py-LEDs) show enhanced maximum luminance, lowered driving voltages, and improved current- and power-efficiencies as compared with the original surface ligand-functionalized QD-LEDs. All three types of QD/py-LEDs show narrow emission spectra (full width at half maximum