EL Devices from Conjugated Polymers with a Low Defect Concentration

2 EL Devices from Conjugated Polymers with a Low Defect Concentration 

In a simplified picture, the EL emission process in the MIM structures can be described in as follows (Fig. 9-21)  

However, the effective internal electric field in tlie device deviates from the field calculated using Eq. (9.10) due to the internally built-in field (see above) because of defect charging in the active layer [55] and interface effects [57]. 

Thus it has been shown that thin insulating layers (in the nanometer range) at the interface metal/polymer in a PLED can significantly reduce the onset electric field necessary for EL [58-63]. This is still not fully understood and has been ascribed to band bending at the interface [64]. 

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