Correlating the Structure of Organic Semiconducting Thin Films with Solar Cell and Transistor Performance (Het verband tussen de structuur van organische halfgeleider dunne filmen en de werking van zonnecellen en transistoren)
Correlating the Structure of Organic Semiconducting Thin Films with Solar Cell and Transistor Performance
Vasseur, Karolien; M0222417
Organic semiconductors have the advantage of being compatible with low-temperature processes and relatively inexpensive deposition techniques, which render them promising candidates for large-area applications on a variety of substrates. Relevant electronic device applications include light-emitting diodes, solar cells and thin-film transistors, each of which must satisfy a specific set of performance criteria. In this work, organic small molecular weight molecules are employed as active componentsin solar cells and thin-film transistors. The individual molecules possess a large anisotropy which dominates the optical and electrical properties in the solid state through the molecular packing arrangement. We try to bring insight into their structure-function relationship and how controlling the thin film structure enables targeting specific functionalities relevant to the intended device. The main part of thisthesis incorporates a comprehensive study that correlates the optoelectronic properties with the structure of non-planar phthalocyanine thin films deposited by vacuum thermal evaporation (VTE), with the objective toachieve near-infrared sensitive solar cells. The influence of deposition conditions, templating layers and post-deposition treatments on the ordering of lead and titanyl phthalocyanine thin films was probed via 2D grazing incidence X-ray diffraction (XRD), specular XRD scans, optical absorption and Raman measurements. The final part of the thesis concerns alow-vacuum deposition technique, organic vapor-phase deposition (OVPD),as a scalable alternative for VTE. We conducted an in-depth growth study of an n-type semiconductor based on a perylene moiety. The presence ofthe carrier gas in OVPD enables higher deposition rates and provides anadditional process parameter for structural control. Hence, the formation of complex interfaces is facilitated and might offer a new route for further enhancement of organic solar cell performance.