Institute of Solid State Physics
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SS22 WS22 SS23 WS23 SS24 WS24 Guidelines for Master Students
Thin Film Forming Properties and Polymorphism of a Benzothieno Benzothiphene Derivative Organic semiconductors (OSCs) offer distinct advantages over inorganic counterparts for thin-film transistor applications. Among them, benzothieno[3,2-b]benzothiophene (BTBT) core-based small molecules are promising as p-type semiconductors. This study investigated the crystal structure, film-forming properties, and polymorphism of OEG BTBT (FD44), a BTBT derivative. High-quality single crystals of FD44 were grown on a Si substrate, revealing a monoclinic phase with a packing arrangement favoring charge transport. We also examined thin film formation through solution processing and physical vapor deposition, achieving mobilities of 6 x 10-4 cm2 V-1 s-1 on devices with physical vapor-deposited OEG-BTBT as the active channel layer. Furthermore, polymorphism studies performed on OEG-BTBT discovered three forms through classical screening and four additional forms employing the surface as a crystallization mediator. Grazing incidence X-ray diffraction (GIXD) analysis was used to collect the lattice parameter information for three-phase pure surface-exclusive polymorphs. Also, for our system of polymorphs, a fascinating memory effect was demonstrated upon recrystallizing from the melt. We conducted a comprehensive analysis using non-ambient temperature-dependent X-ray diffraction and hotstage microscopy techniques. After the analysis, we could conclude that the potentiality of recrystallizing into the same phase is limited to a particular temperature value. Moreover, we could successfully illustrate the melting point, induction time, and crystal growth kinetics associated with these new polymorphic forms. In summary, our findings shed light on the crystal structure, film properties, and polymorphism of OEG-BTBT, exploring its potential for organic electronic devices and uncovering insights into memory effects in polymorphic systems. |
