Device physics of organic field effect transistors and organic photovoltaic devices
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In this dissertation novel work is presented showing the performance and device physics of Organic Field Effect Transistors (OFETs) and bulk heterojunction Organic Photovoltaic (OPV) devices fabricated using novel acceptor small molecules. Pentacene and N,N’-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN₂) were used as the active layer in p-channel and n-channel Organic Field Effect Transistors (OFETs), respectively, and novel pulsed voltage transient measurements were developed in order to extract transient mobilities and carrier velocities from the transistor response of the device, which were well correlated with the corresponding DC OFET characteristics. A distributed RC network was used to model the OFET’s channel and the transient and DC characteristics of the devices were successfully reproduced. Temperature dependent studies of the DC field effect mobilities and transient mobilities of these two materials were carried out and the results used to extract information on charge carrier transport in the materials at varying time scales. Open-circuit voltages of the OPV devices are correlated with the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) levels various acceptor small molecules and donor polymers comprising the active layers of the devices.