Switching alternating current (AC) using a fully screen-printed current-driven transistor

The authors report on a large area, fully screen-printed transistors, using nanostructured silicon as the active material. The transistors are produced by simple screen printing processes under ambient conditions without the need for post-processing steps. The devices can be operated as two-way switches both with a direct or alternating current (AC). The authors demonstrated the operation of the devices printed on flexible substrates (office paper 80 g/m2) using silver as the conductive electrodes and highly doped p-type nanostructured silicon as the active layer. A method of switching sinusoidal AC using a single printed transistor is demonstrated at a frequency of 50 Hz at ambient condition. The silicon used as active materials, present domains, and blocks at a microscopic level, with an electric behaviour similar to one of the varistor-like components used as surge suppressors. So, unlike conventional transistors which rely on electric field modulation or charge injection, these AC switches operate by activation transport of charge carriers in the active silicon layer. Switching AC is achieved by applying a signal to the base which results in a change of the current's direction from between the collector and base to between the base and emitter.