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ARCO Laboratory (ARCOLAB)

The device is normally composed by a organic film (the active material) sandwiched between ITO (Indium Tin Oxide) layer acting as anode and an Aluminium layer acting as cathode. It is also possible to place as cathode a layer of Calcium to increase the electrons injection in the active layer and even a film of PEDOT between the ITO and the organic film to increase holes injection. The I/V caracteristics of the devices are measured by Keithley 236. The light produces by the electroluminescent active layer comes out from the ITO layer (transparent to visible light) and its intensity is measured by a photodiode place in front of the device. A spectrum of the electroluminescence can be taken by an Optical Multichannel Analyzer (OMA). The figure shows a representation of the device.

The main instruments used in this laboratory for material realization are: an extractor fan, an evaporator, a spin-coater, a precision scale and a little heater.

The preparation of solutions occurs in the extractor fan to prevent gas inhalation. In this step are used the scale and the heater to control sensitive parameters of the process.

Using the evaporator it is possible to make organic and polymer films through the sublimation af the target in high-vacuum (10-6 mbar). With this method can be achived thickness between 1 nm to few mm.

Spin-coater is used to produce just organic films. The rotation of the substrate induce an uniform distribution of the solution on the top of the substrate itself accomplishing the evaporation of the solvent. This approach produce amorphous films with thickness in the range between few tens to hundreds nanometers.

 

The electric field-assisted pump-probe technique allows for studying fundamental processes in electroluminescent devices, such as charge generation and recombination. The device, in vacuum, is composed by an organic film (the active material) sandwiched between an ITO (Indium Tin Oxide) layer (acting as anode) and an Aluminium layer (acting as cathode). The pump and the probe laser beams are spatially and temporally overlapped on the sample; there is a temporal delay Dt between the two pulses. Both beams go through the sample and are reflected by the aluminium layer, but only the probe pulse is detected. Applied electric fields are approximately in the order of MV/cm2. Using this technique it’s possible to measure small variations in the probe transmission, in presence of the pump beam, induced by the applied electric field.



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