14
Doping of Organic Semiconductors
14.1 Introduction
In today's production of semiconductor devices, single-crystalline silicon is by far the most frequently used material among other inorganic crystalline materials like GaAs by a wide margin. These materials are stable and offer room temperature mobilities up to 1000 cm2/(V s). However, they are less suitable for low-cost or large area applications. For optoelectronic applications like solar cells and light-emitting diodes, silicon is again less appropriate because it is an indirect semiconductor. Therefore, silicon solar cells need rather thick material layers, resulting in higher cost and long payback time.
A recently much-noticed alternative is organic semiconductor, that is, molecular semiconductor consisting of carbon-based molecular entities. Although early research on organic semiconductors focused on single-crystalline organics whose mobilities, which were investigated in the pioneering work of Karl [1], reach from a few cm2/(V s) at room temperature to a much higher values at reduced temperatures, the thin-film organic semiconductors are preferred today due to practical reasons. The two groups of such materials, the polymers processed from solution and the evaporated small-molecule compounds, are already included in present products, for example, as photoconductors in copiers and laser printers. The field has been recently reviewed by several authors; we however refer here to ...
