The impact of the third component on the microstructure of novel ternary blend thin films incorporating non-fullerene acceptors for organic solar cells

The performance and long-term stability of scalable bulk-heterojunction organic solar cells based on non-fullerene acceptors are still significantly constrained by issues related to charge carrier recombination, morphological instability, and trap-induced losses. One approach to mitigate these issues involves adding a third component into the photoactive layer. Such ternary blends aim to boost the power conversion efficiency – for example, by broadening the light absorption, reducing the defect density, improving morphology- or even to increase their transparency and processbility by incorporating two photoactive materials into an inert polymeric host matrix. It is crucial to understand the morphological interplay of the three different components to guide material selection and processing conditions.

This experiment investigates the use of an inert or functional third component in donor–acceptor blends for OSCs, with the goal of improving charge transport, reducing recombination via defect suppression, and enhancing morphological and thermal stability. The central hypotheses are i) a proper material choice of the third component can have a positive impact on the miscibility, π-π stacking, and phase demixing, and ii) while adding an insulating polymer as a third component reduces absorption, it may also significantly reduce trap-assisted recombination (superlinearly); in that scenario, increasing the active layer thickness allows for compensation without a performance penalty. Furthermore, the decrease in acceptor aggregation induced by the addition of the third component may enhance the performance of OSC and/or their thermal and photochemical stability, although the microscopic mechanisms governing these improvements remain largely unknown.