Dynamic optoelectronic characteristics of advanced organic solar cells
Andreas Klary
Institute for Chemistry and Technology of Materials, TU Graz
11:15 - 12:15 Wednesday 11 March 2026 Organic solar cells represent a promising class of next-generation photovoltaic technologies due to their tuneable optoelectronic properties, lightweight character and potential for low-cost, large-area fabrication. Recent advances in materials design and device engineering have enabled organic photovoltaic devices to reach power conversion efficiencies beyond 20% at the laboratory scale. In this thesis, the performance and dynamic charge transport and recombination characteristics of in-house fabricated OSCs were investigated using a specially developed and installed measurement setup. The investigated OSC systems comprised different active layer blends as well as, in part, different hole transport layers. In a first characterization step, current density–voltage (J–V) measurements were performed under standard solar illumination conditions to determine key photovoltaic parameters, including short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency.
To gain deeper insight into the fundamental processes, which are governing the device performance, transient photocurrent (TPC) and transient photovoltage (TPV) techniques were applied. These time-resolved measurements enabled the investigation of charge carrier lifetime, extraction and recombination behaviour under different operating conditions. In particular, the TPC measurements revealed differences in charge transport and collection efficiency among the investigated systems, while TPV decay kinetics provided information about the recombination dynamics. The combination of both methods provided further understanding the key processes controlling the performance of the investigated organic solar cells.
By comparing the properties of solar cells with the active layer compositions PM6:Y6, D18:L8-BO and PM6:BTP-eC9 and additionally varying the composition of the hole transport layers (PEDOT:PSS, 2PACz, PEDOT:PSS/2PACz bilayer), distinct differences in the dynamic behaviour of the examined OSC devices were observed. An additional comparison of fresh and aged solar cells delivered insights into degradation-related changes of OSC properties. Overall, the experimental findings demonstrate that combining steady-state and transient characterizations is a useful approach to correlate the overall device performance to charge carrier dynamics that largely determine the operation and efficiency of organic solar cells.
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Institute of Solid State Physics
