Two-dimensional crystals of organic semiconductors: from material to electronic properties and device performance

We will bridge the gap between the intrinsic (ground and excited) electronic properties of organic semiconductors and their transport properties in the corresponding devices by the growth and study of two-dimensional crystals of organic semiconductors (2DCOS) films, a class of ultrathin crystals with molecular level thickness and millimeter-scale-lateral dimension.

Our goals are: (i) map the band structure of 2DCOS by angle-resolved photoemission spectroscopy (ARPES) upon theoretical calculation to estimate the low limit mobility of the conducting holes. (ii) reveal anisotropy of exciton dispersion along crystal axes by inelastic electron scattering, also called momentum-dependent electron energy-loss spectroscopy (EELS) in transmission, with admixture of Frenkel-charger transfer excitons model. (iii) study organic field-effect transistor devices  from the same large crystal film, as used in ARPES/EELS, to reliably correlate their charge transport properties in devices with the results from electronic properties approach to disentangle the transport mechanism.

To achieve these goals, we will utilize and extend “solution assembly” process to grow large-area (mm2 -- cm2) 2DCOS films with precise control of the thickness (from monolayers up to 100 nm) to offer all studies on the same film and to overcome the sample charging that hampers many surface science techniques.

The work will be for a PhD student in 4-years assisted by senior researchers.