Electronic properties of interfaces between domains inorganic semiconductors

by Marko 1988- Mladenovi

Institution: Univerzitet u Beogradu
Year: 2017
Keywords: organski poluprovodnici; elektronska struktura; granicadomena; termalna neuredenost; kristalni domen; amorfni domen; spontana polarizacija
Posted: 02/01/2018
Record ID: 2153787
Full text PDF: https://fedorabg.bg.ac.rs/fedora/get/o:15291/bdef:Content/get


Electrical and Computer Engeneering -Nanoelectronics and Photonics / Elektrotehnika i raunarstvo -Nanoelektronika i fotonika The aim of this thesis is to provide a link betweenatomic and electronic structure of different types of interfacesbetween domains in organic semiconductors. In polycrystallinesmall-molecule organic semiconductors interfaces are formed betweensingle crystalline domains. We found that grain boundaries inpolycrystalline naphthalene introduce trap states within the bandgap of the material. Trap states are localized on closely spacedpairs of molecules from opposite sides of the boundary. Realisticconjugated polymers, such as poly(3-hexylthiophene) (P3HT), containmixed crystalline and amorphous domains. We found that HOMO stateof the interface between crystalline and amorphous domain in P3HTbelongs to crystalline domains. States that belong to both domainsand trap states were not found. Effects of thermal disorder areimportant in realistic conjugated polymers. Our results show thatdisorder in backbone chains of P3HT has strong effect on theelectronic structure and leads to the localization of the wavefunctions of the highest states in the valence band, similar to theones that occur in amorphous polymers. At the interfaces betweentwo materials in organic electronic devices, effects of spontaneouspolarization in one or both of them on electronic properties can bepronounced. We show that ordered P3HT exhibits spontaneouspolarization along the backbone direction, which is caused by thelack of inversion symmetry due to head-to-tail side chainsarrangement. We additionally show that spontaneous polarization inordered P3HT keeps significant values even at room temperature whenthe effects of thermal disorder are important.Advisors/Committee Members: Radovanovi, Jelena, 1973-.