Energy structure, electroluminescent

PbS has attracted much attention due to its special direct band gap energy (0.4 eV) and a relatively large exciton Bohr radius (18 nm) and their nanoclusters have potential applications in electroluminescent devices such as light-emitting diodes. PbS nanocrystals with rod like structures with diameters of 20-60 nm and lengths of 1-2 pm have been obtained using the sonochemical method and by using PEG-6000 [66]. Addition of PEG and the time of sonication have been found to play a key role in the formation of these rods. 

Electroluminescence (EL) is the phenomenon by which electrical energy is converted into luminous energy by the recombination of electrons and holes in the emissive material [8], The basic structure of an OLED consists of a thin film of organic material sandwiched between two electrodes, an anode of high-work-function material such as indium tin oxide (ITO) on a glass substrate, and a cathode of a low-work-function metal such as calcium (Ca), magnesium (Mg), or aluminum (Al) or an alloy such as Mg Ag. 

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