Assembly Of Light-emitting Diode Based On Hydrophilic CdTe Quantum Dots

Quantum dot light emitting devices(QD-LEDs)are a new generation of LEDs,which have attracted much attention in recent years,possessing unique properties of tunable emission wavelengths by controlling the size of the QDs,highly saturated emission,narrow emission with small full width at half maxima(FWHM).At present,the emitting layers of QD-LEDs are almost entirely QDs synthesized in organic solution via an organometallic route which are expensive and can't be mass-produced.What's more,the organic solvents of the oil phase QDs are poisonous.Therefore,to fabricate a new QD-LED based on the low-cost,environmentally-friendly and processable aqueous QDs has become one of the new exploration directions.In this paper,two different kinds of aqueous CdTe QD-LEDs are fabricated respectively by photoluminescence method and electroluminescence method.And the essential factors of fabricating aqueous QD-LEDs successfully are also explored.An aqueous red(650nm-700nm)CdTe QD-LED is fabricated successfully with structure of ITO/PEDOT:PSS/PVK/CdTe QDs/ZnO/Al.The device represents an EL turn-on at the forward voltage about 5V,and its current density and brightness reach to 92mA/cm2 and 58cd/m2 at the voltage of 10V.This work would provide support of process and parameter designing for other aqueous QDs applied in QD-LEDs.There are two essential processes to fabricate an aqueous QD-LED successfully:adding wet agent to QDs solution and removing the complex ions remaining in the QDs solution.Adding wet agent can reduce the surface tension of water and improve the quality of the hydrophilic QDs layer formed on top of the hydrophobic hole transport layer substrate.Removing complex ions would prevent them from disrupting the electron-hole recombination in the QD layer.What's more,the acidity or alkalinity of the aqueous QDs solution is not essential factor for fabricating aqueous QD-LEDs successfully,but acidic solvent of QDs are benefit to the luminescence of aqueous QD-LED.This work would provide effective reference data for fabricating more efficient and more kinds of aqueous QD-LEDs.By freeze drying method,a quantum dot-inorganic nanocomposite(hydrophilic CdTe QDs incorporating dehydrated silica gel)is prepared with unique properties of viscosity,plasticity and transparency.A photoluminescence aqueous CdTe QD-LED can be fabricated by coating the dehydrated silica gel on the ultraviolet LED.This new method is environmentally non-toxic,easy to operate,low cost and can be long-term preserved.It will expand the applications of aqueous CdTe QDs in photoluminescence LED.