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HL: Fachverband Halbleiterphysik

HL 28: Focus: Exploitation of Anisotropy in Organic Semiconductors I (joint session CPP/HL)

HL 28.5: Hauptvortrag

Dienstag, 17. März 2020, 11:30–12:00, ZEU 222

Influence of stability and molecular orientation on the properties of stable glasses — •Javier Rodríguez-Viejo — Physics department, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

Stable glasses have attracted great interest since their discovery in 2007. Their superior behavior, compared to liquid-cooled glasses, includes higher kinetic and thermodynamic stability, higher density, sound velocity and elastic moduli or the modification of the low-temperature properties. The origin of the high thermodynamic and kinetic stability of these vapor-deposited glasses is related to the high mobility of surface molecules that enables them to settle into energetic favorable positions during the deposition process. Besides, depending on the molecular shape PVD glasses exhibit packing anisotropies that depend on the deposition temperature. Although molecular orientation does not seem to play a substantial role in the observed stability enhancement, it can have a significant impact in many properties of vapor-deposited glasses. For instance, we have previously shown that molecular orientation may induce variations of the growth front velocity during the heterogeneous transformation of a glass into the supercooled liquid state. In addition, molecular anisotropy plays a key role in charge and thermal transport. We will describe the impact of the deposition process and the molecular orientation on the thermal properties and on electronic and heat propagation. We also explore the benefits of using stable glasses grown at temperatures around 85% Tg to increase device efficiency and operational stability of OLEDs.