| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
EE4, Charge Trapping and Localization Due to Paracrystalline Disorder in High Performance Polymeric Semiconductors |
| Author(s) |
Rodrigo Noriega, Jonathan Rivnay, John E. Northrup, R. Joseph Kline, Michael F. Toney, Alberto Salleo |
| On-Site Speaker (Planned) |
Rodrigo Noriega |
| Abstract Scope |
Disorder within crystallites of organic semiconducting materials has been shown to be strongly linked with electronic processes. One type of disorder is positional fluctuations within the crystalline regions of semicrystalline polymers. The positional fluctuations of monomer units in these materials are described by the paracrystallinity model developed by Hosemann et al. An experimental, quantitative measure of the disorder parameters inside polymer crystallites is performed using the X-ray diffraction lineshape analysis of Warren and Averbach. The use of synchrotron radiation and a variety of diffraction geometries allows us to study disorder in the different crystallographic directions even for weakly scattering materials like semicrystalline semiconducting polymers. The usual assumption of 3D ordering in crystalline domains is disputed, since one of the most ordered materials in the lamellar direction, the high performance p-type polymer PBTTT, is strongly disordered in the π-stacking direction. This highly disordered character in a direction which is closely related to charge transport is present in a variety of materials reported in the literature. The implications of such a disordered behavior are studied with a tight binding model using density functional theory calculations to determine the intersite transfer integral. Localized tails in the DOS due to disorder can have a significant effect on electronic and optical properties of these materials. A closed-form expression for the DOS of an ensemble of paracrystalline 1D chains, as well as for a localization length of states in the tail is obtained. Increasing the paracrystalline disorder has the double effect of creating a tail of localized states, but also decreasing the delocalization length of states in the band. For extremely large values of paracrystallinity, the band disappears and we are left with a single population of localized states. Thus, the validity of different charge transport models such as the mobility edge or hopping in a localized DOS can be verified by quantitatively measuring lattice disorder in the crystallographic directions related to charge transport in organic semiconductors. |
| Proceedings Inclusion? |
Undecided |