Nanostructures charge carrier collection

In this section we focus on optoelectronic devices that are based on either the emission or the absorption properties of polymer nanofibers, jointly with transport properties that are needed to lead charge-carriers to either radiatively recombine (as in OLEDs) or separate photo-generated excitons to collect charges (as in photo-detectors or solar cells). These nanofiber-based devices combine photonic and charge-transport features of polymer nanostructures. The charge-carrier transport properties of nanofiber materials are described in detail in Chapter 6. 

To summarise these few experimental results, it can be stated that electronic transport in many nanostructured polycrystalline materials appears to be rather poor, particularly when the transport path involves grain boundaries. Yet in many cases the transport conditions can be improved by operating these films under majority-carrier transport conditions and exploiting trap filling under high-injection conditions. Efficient charge collection can then often be achieved. In absorber layers, where both carrier types are necessarily present, these conditions cannot usually be implemented. 

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