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Charge transfer processes and carrier dynamics at the pentacene - C60 interface
摘要： Heterostructures of pentacene (PEN) and Buckminsterfullerene (C60) are frequently attracting scientific interest as a well-defined small-molecule model-system for the study of internal interfaces between two organic semiconductors. They are prototypical representatives forming a donor-acceptor combination for studies of fundamental optoelectronic processes in organic photovoltaics. Despite their importance in exciton dissociation, the energetics of their interfacial charge-transfer (CT) states and their microscopic excitation dynamics are not yet clarified and still being discussed. Here, we present steady-state and time-resolved photoluminescence measurements on stacked heterostructures between these two materials. All experiments are performed in the visible and near-infrared spectral regions as CT states are expected at energies below the fundamental electronic transitions of the respective bulk materials. A characteristic, interface specific emission at around 1.13-1.17 eV is found, which we attribute to an interfacial CT state. Its excitation-energy dependence reveals the intricate relaxation dynamics of excitons formed in both constituent materials. Moreover, the analysis of the dynamics of the C60 excitons shows that the lifetime of this state is reduced in the presence of an interface with PEN. This quenching is attributed to a long-range interaction, i.e., the relaxation of excitations into the interfacial CT state.
关键词： organic heterostructures,charge-transfer exciton,light harvesting,donor-acceptor pair,Organic thin films,pentacene,fullerene
更新于2025-09-23 15:22:29
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Organic–Organic Heterostructures
摘要： Thin films of organic molecules are now of technological importance as the active component in modern electronic and optoelectronic devices, such as organic light-emitting devices, organic thin-film transistors, organic sensors, and organic photovoltaic devices. After a first era of general excitement, it was soon discovered that to be able to rival their inorganic counterparts, one has to control the structure, crystallinity, and morphology during thin-film growth and understand and control their molecular electronic properties. An important topic therein is the formation of interfaces, specifically the organic-metal interface, which acts as the contact. Consequently, the growth and the electronic level alignment (band alignment) of organic molecules on metal surfaces have been extensively studied for the last 20 years. However, organic devices in general comprise more than one organic layer. As a consequence, we also have to consider organic–organic interfaces and the electronic level alignment across them and how heteroorganic films form. In comparison with the huge number of publications dealing with organic film growth on metal, the literature of controlled surface science studies of organic film growth on an organic layer is rather scarce. And indeed, there are a number of challenges one has to be aware of, when investigating organic heterostructure formation. In contrast to metal single-crystal substrates, which are available in every orientation, organic single crystals, large enough to handle with surface science methods, are hardly available, let alone in various orientations. The best approximation to a single crystal is organic thin films composed of crystallites of the same orientation that tile the substrate surface. By careful selection of the inorganic substrate and growth conditions, a number of orientations can be achieved. A second difficulty is that many surface science methods use electrons and thus can be prone to charging and beam damage particular for thick films.
关键词： electronic devices,optoelectronic devices,thin films,organic-metal interface,Organic–organic heterostructures,molecular electronic properties
更新于2025-09-09 09:28:46