Indium Phosphide-Based Colloidal Quantum Dot Light-Emitting Diodes on Flexible Substrate

Colloidal quantum dots (QDs) are very promising nanomaterials for future information display. Since traditional Cd-based colloidal QDs are not environmental friendly, heavy metal-free quantum dots are desirable for quantum dot light-emitting diodes (QD-LEDs). We report the QD-LEDs using InP/ZnSe/ZnS multishell colloidal QDs prepared by simple heating-up synthesis, which was fabricated on polyethylene naphthalate (PEN) substrate for flexible optoelectronic device. The electroluminescent (EL) performance of QD-LEDs on different PEN substrates was compared by the factors of sheet resistance and surface roughness of ITO substrate. The maximum current efficiency of InP-based QD-LEDs on ITO/PEN substrate enhanced up to 1.6 cd/A from 1.0 cd/A by controlled carrier balance by ITO characteristics, which was comparable with the performance of device fabricated on glass substrate (maximum current efficiency: 1.98 cd/A). Our flexible QD-LEDs maintain the consistent luminance after 1200 times of bending cycle with 50 mm of curvatures as well. The performances of our device are not matched with Cd-based QD-LEDs yet, however it shows the great potential for various flexible and eco-friendly information displays.