Experimental Physics VI

    Organic Electronics

    “Organic Electronics” is a rapidly advancing field and, in recent years, has entered consumer applications by means of organic light-emitting diode (OLED) displays in mobile phones and home entertainment systems.

    In this context, our research is concentrated on electronic excitations in molecular single crystals, crystalline thin films as well as single molecules and their interplay with the structural and electronic characteristics on nanometer length scale [1]. Disclosing the fundamental processes together with their dependence on morphology and temperature allows for a fundamental understanding and, thus, improvement of the device performance of organic field-effect transistors (OFETs), organic photovoltaics (OPVs) as well as OLEDs [2,3]. This knowledge also paves the way towards future, quantum-based functional units such as electrically driven molecular single photon sources or organic lasers both studied in our group [4].

    The areas of interest of our scientific activities comprise the impact of the crystal structure on the emission properties under optical as well as electrical excitation, molecular sensors to probe the charge density distribution and local polarization fields at nanometer scales and, thereby, to carry-out non-invasive lifecycle analyses on OLEDs and OFETs under operation. Moreover, we aim for new molecules for advanced lighting in the NIR and IR [5] and ultra-fast photo-switches based on low-dimensional organic metals [6].

    Experimental infrastructure:

    • Purification of molecular materials by gradient sublimation
    • Crystal growth from vapor, melt, solution and electro-crystallization
    • Ultra high vacuum physical vapor deposition for thin film and device preparation
    • Structural characterization by X-Ray diffraction and atomic force microscopy
    • µ-Photoluminescence together with lifetime analysis from 4 K to 400 K
    • Confocal microscopy in combination with photon correlation measurements

    If you are interested in a specific topic of our research or are looking for a master thesis feel free to contact Prof. Jens Pflaum for general questions or, for a specific topic, the responsible staff member:

    [1] Effects of characteristic length scales on the exciton dynamics in rubrene single crystals
    Gieseking B, Schmeiler T, Müller B, Deibel C, Engels B, Dyakonov V and Pflaum J (2014). Phys Rev. B 90(20), 205305. [DOI]

    [2] The Effect of Gradual Fluorination on the Properties of FnZnPc Thin Films and FnZnPc/C60 Bilayer Photovoltaic Cells 
    Brendel M, Krause S, Steindamm A, Topczak AK, Sundarraj S, Erk P, Höhla S, Fruehauf N, Koch N and Pflaum J (2015). Adv. Mater. 25(10), 1565-1573. [DOI]

    [3] Thickness dependent effects of an intermediate molecular blocking layer on the optoelectronic characteristics of organic bilayer photovoltaic cells
    Steindamm A, Brendel M, Topczak AK and Pflaum J (2012). Appl. Phys. Lett. 101(14), 143302. [DOI] [URL]

    [4] Electrically driven photon antibunching from a single molecule at room temperature 
    Nothaft M, Hoehla S, Jelezko F, Fruehauf N, Pflaum J and Wrachtrup J (2012). Nature Comm. 3, 628 [DOI]

    [5] Optoelectronic Processes in Squaraine Dye-Doped OLEDs for Emission in the Near-Infrared
    Stender B, Völker SF, Lambert C and Pflaum J (2013). Adv. Mater. 25(21), 2943-2947. [DOI]

    [6] Ultrafast Pathways of the Photoinduced Insulator-Metal Transition in a Low-Dimensional Organic Conductor
    Smit B, Hüwe F, Payne N, Okaoye O, Bauer I, Pflaum J, Schwoerer M and Schwoerer H (2019).  Adv. Mater. [DOI]