Voltage tunable electroluminescence of CdTe nanoparticle light-emitting diodes

Strong electroluminescence was observed in a CdTe nanoparticle light-emitting diode that was fabricated by layer-by-layer assembly of poly(p-phenylenevinylene) and CdTe nanoparticles. The turn-on voltage for the electroluminescence is 4.0 V. The electroluminescence is exclusively from CdTe nanoparticles, with a 30 nm red shift in emission wavelength from the photoluminescence and shifts to longer wavelengths at higher applied voltages. Possible mechanisms for this red shift are discussed, and it is concluded that the de-trapping of surface states and trap centers due to electric excitation, the involvement of traps in the electroluminescence, and the quantum confined Stark effect are the major reasons for the red shift.