Understanding and suppressing interfacial charge recombination for high performance perovskite solar cells (SURPRISE II)

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During the first funding period, the SURPRISE project aimed at unravelling the processes that govern interfacial recombination in high performance pin-type cells with organic charge transport layers, with particular focus on understanding the interfacial recombination pathways, the energy level alignment at the interface, as well as the operation mechanism of interlayers and back-surface fields due to doping. The project has also opened up new research directions, by developing advanced opto-electronic characterization methodologies, by identifying a novel operando energy level alignment phenomenon, and by highlighting the role of mobile ions and of the built-in field on device performance. In the proposed follow-up project SURPRISE II, the same team from the first funding period will address demanding research questions of highest topicality with respect to interfacial recombination and defect states. In particular, we will focus on the impact of the grain size, surface and interface chemistry, doping, and crystal strain on the interfacial recombination losses. New research objectives aim at unraveling the impact of interfaces on device ageing and degradation, and the development of advanced experimental methodologies to reliably determine the built-in voltage and the entire solar cells’ band diagram – in the ground state and under operation conditions. Furthermore, we target providing comprehensive understanding of the impact of mobile ions on interfacial recombination, especially with respect to device degradation. Finally, based on our findings in the first funding period with regard to the location of the dominant interfacial recombination loss, point contacts with electron TLs in combination with newly designed interlayers will be developed to reduce the contact area between the perovskite and the TL. Overall, the SURPRISE II project will establish novel principles to systematically mitigate interfacial recombination for efficient and more stable pin-type cells approaching 25% power conversion efficiency.