Integrated Computational Materials, Process and Product Engineering – IC-MPPE 2022

Devices for the Internet-of-Things are often placed in remote locations or are embedded in vehicles or machines and thus need to be energy-autonomous. Highly promising energy sources are perovskite-based solar cells, that have overwhelmed the field of photovoltaics with skyrocketing efficiencies, while simultaneously allowing light weight and cost efficient fabrication and hence a low energetic (and financial) uptake. For integration it is of the essence to store superfluous energy for timespans of darkness. Here providing high charging voltages is an important component for energy density in batteries and even more in capacitors. Unfortunately voltages of high efficiency single solar cell architectures are limited by the optimal band gap for light absorption, which is why tandem concepts are highly desirable, where the voltages of sub-cells add up and are able to advance into formerly unreachable areas.
Here, we demonstrate perovskite/organic tandem cells with an open circuit voltage of 2.2V and efficiency of 24%. This sets a new milestone for these type of tandem devices with a realistic prospect of reaching >31%.
This progress is based on a threefold approach:
- In surprising contrast to these almost paradigmatic concerns, we
evidenced an outstanding operation stability of organic single
junctions that are based on the PM6:Y6 active system, if operated at
tandem-like conditions.
- We managed to overcome interfacial losses, that are the predominant
reasons limiting the output voltage of wide-gap perovskite cells. At
the same time, our findings evidence that the proper choice of charge
extraction layers can mitigate some detrimental degradation
mechanisms inside the cell.
- We introduce a novel recombination interconnect for the two
sub-cells, that is based on an ultra-thin (1.5nm) metal-like indium
oxide layer. This interconnect offers unprecedented low optical and
electrical losses, which unlocks the exploitation of the full
potential of the two sub-cells without any discount.