One of the important challenges in the field of thin-film transistors is to improve designs that result in performance speeds to the GHz level. With polymer semiconductors, non-quasistatic circuits such as rectifiers in which the maximum frequency depends on the carrier transit time, have been demonstrated to work to a few 10’s of MHz. The challenge is to realize clocked sequential circuits that operate as speeds much larger than the few 10’s of kHz that have been demonstrated so far. One of the keys to this, which has received a lot of attention, is improved carrier mobility in new materials. It is also necessary to reduce the channel length considerably without serious degradation in performance. We present designs based on nanostriped polymer and other semiconductors that are very suitable for scaling down the channel length. We show that in such devices, we can achieve enhanced carrier densities and mobilities compared to regular planar devices at all channel lengths. Importantly, we can also potentially reduce the contact resistance on account of the high conductivities that result from this geometry. This will be helpful in reducing channel length. A nanostriped geometry also improves gate control and reduces short channel effects. With our optimized TFT model we demonstrate all these effects. We also compare our model predictions with experimental data from organic and polymer transistors.
We review the key optoelectronic properties of lateral organic bulk heterojunction (BHJ) device structures with asymmetric contacts. These structures are used to develop a detailed model of charge transport and recombination properties within materials used for organic photovoltaics. They permit a variety of direct measurement techniques, such as nonlinear optical microscopy and in situ potentiometry, as well as photoconductive gain and carrier drift length studies from photocurrent measurements. We present a theoretical framework that describes the charge transport physics within these devices. The experimental results presented are in agreement with this framework and can be used to measure carrier concentrations, recombination coefficients, and carrier mobilities within BHJ materials. Lateral device structures offer a useful complement to measurements on vertical photovoltaic structures and provide a more complete and detailed picture of organic BHJ materials.