The growth and material system of organic semiconductor devices

Abstract:

Organic semiconductor devices have widely used in display, energy-storage device, and consumable electronics. In this thesis defense, I demonstrate how we can improve performance of organic semiconductor devices in terms of material property and process development.

In the first part, organic vapor phase deposition (OVPD) is shown to control morphology of organic thin-film. Under various growth condition of OVPD, fullerene molecule in other small-molecule organic matrix tends to form crystal domain, thereby enhancing charge transport through fullerene domains. This enhanced charge transport leads to the higher power-conversion efficiency (PCE) of the organic photovoltaics (OPV) compared to the equivalent device grown by conventional vacuum thermal evaporation. In addition, organic thin-film grown by OVPD has rough surface from nano-crystallites, further inhibiting the degradation of over-layer.

Secondly, I demonstrate the design of organic semiconductor devices with new class of materials. Co-polymer containing fullerene unit helps to prevent phase segregation of P3HT:PCBM polymer bulk-heterojunction OPV. At the same time, conductivity of the polymer layer is significantly increased from the fullerene unit in co-polymer. Lastly, in organic light-emitting diode (OLED), I adopt purely organic phosphors in the device and explain the device structure with this new class of emissive material.