Organic semiconducting devices have many positive attributes, such as their low cost, high flexibility, light weight, and ease of processing. However, one drawback of organic semiconductors is that they generally have a low electron mobility, resulting in a weak current and poor conductivity.
In a new study, scientists from Taiwan have designed and built an organic semiconductor transistor with a mobility that is 2-3 orders of magnitude higher than that of conventional organic semiconductor transistors. The benefits of a high mobility could extend to a wide range of applications, such as organic LED displays, organic solar cells, and organic field-effect transistors.
The biggest reason for low electron mobility in conventional organic semiconductors is electron scattering due to structural defects in the form of grain boundaries. By designing an organic semiconductor transistor containing only a single grain, the scientists could avoid the problem of grain boundary scattering.
In their experiments, the researchers demonstrated that a device containing a single organic nanoparticle (perylene tetracarboxylic dianhydride, PTCDA) embedded in a nanopore and surrounded by electrodes achieves the highest electron mobility value to date by 1 order of magnitude, and is 2-3 orders of magnitude higher than the values reported for conventional organic semiconductor transistors made of polycrystalline films. The new device's mobility values are 0.08 cm2/Vs at room temperature and 0.5 cm2/Vs at a cool 80 K, which are approaching the intrinsic mobility of PTCDA.