Coordination Funds

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The goal of the Research Unit POPULAR is to investigate the printing of efficient organic solar cells based on non-fullerene acceptors (NFAs). While printing of photovoltaic devices is usually done by industrially focused development with a view to commercialisation, we are convinced that the impact of printing on film formation and specific microstructure of organic solar cells deserves a detailed fundamental investigation: Our joint theoretical and experimental approach is designed to develop a deep understanding of the function–property relationships. We will apply gravure printing to first print the photoactive layer of the solar cells from different donor–acceptor combinations under systematically varied processing conditions. First, we will only print the active layer, and deposit the other layers by spin-coating and thermal evaporation. Thereafter, we will process fully-printed devices. Lab-scale spin-coated devices with the same solar cell stack will serve as reference. We will focus our study particularly on the photophysics, optical properties, energetics in dependence on the nanomorphology. This information will be combined with the photogeneration and recombination processes measured under working conditions, and modelled using multi-experiment fitting by numerical device simulations. We will use promising, commercially available NFAs to establish the printing processes, select the device architecture. Later on, novel donor NFA multiblock co-oligomers with monodisperse segments of predefined length – which will be synthesised in this Research Unit – to yield a thermodynamically stable lamellar morphology, will be integrated into printed single-component solar cells. An important aspect of this proposal will be on understanding intrinsic stability, limiting the device performance over time, and minimising degradation. With our combined, complementary approach, we will gain deep insight into the function–property relation of novel, printed fullerene-free organic solar cells, while developing the printing process tailored to the best photovoltaic performance.