@phdthesis{Gruene2022, author = {Gr{\"u}ne, Jeannine}, title = {Spin States and Efficiency-Limiting Pathways in Optoelectronic Materials and Devices}, doi = {10.25972/OPUS-29340}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293405}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {This thesis addresses the identification and characterization of spin states in optoelectronic materials and devices using multiple spin-sensitive techniques. For this purpose, a systematic study focussing on triplet states as well as associated loss pathways and excited state kinetics was carried out. The research was based on comparing a range of donor:acceptor systems, reaching from organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) to organic photovoltaics (OPV) employing fullerene and multiple non-fullerene acceptors (NFAs). By developing new strategies, e.g., appropriate modeling, new magnetic resonance techniques and experimental frameworks, the influence of spin states in the fundamental processes of organic semiconductors has been investigated. Thereby, the combination of techniques based on the principle of electron paramagnetic resonance (EPR), in particular transient EPR (trEPR) and optically detected magnetic resonance (ODMR), with all-optical methods, such as transient electroluminescence (trEL) and transient absorption (TA), has been employed. As a result, excited spin states, especially molecular and charge transfer (CT) states, were investigated in terms of kinetic behavior and associated pathways, which revealed a significant impact of triplet states on efficiency-limiting processes in both optoelectronic applications.}, subject = {Elektronenspinresonanz}, language = {en} } @phdthesis{Weissenseel2022, author = {Weißenseel, Sebastian G{\"u}nter}, title = {Spin-Spin Interactions and their Impact on Organic Light-Emitting Devices}, doi = {10.25972/OPUS-25745}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257458}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {This work investigates the correlations between spin states and the light emission properties of organic light-emitting diodes (OLEDs), which are based on the principle of thermally activated delayed fluorescence. The spin-spin interactions responsible for this mechanism are investigated in this work using methods based on spin-sensitive electron paramagnetic resonance (EPR). In particular, this method has been applied to electrically driven OLEDs. The magnetic resonance has been detected by electroluminescence, giving this method its name: electroluminescence detected magnetic resonance (ELDMR). Initial investigations on a novel deep blue TADF emitter were performed. Furthermore, the ELDMR method was used in this work to directly detect the spin states in the OLED. These measurements were further underlined by time-resolved experiments such as transient electro- and photoluminescence.}, subject = {Elektronenspinresonanz}, language = {en} }