Regensburg 2019 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Hybrid and Perovskite Photovoltaics II

CPP 19.3: Talk

Tuesday, April 2, 2019, 10:00–10:15, H18

Highly Efficient monolithic perovskite silicon tandem solar cells: analysing current-mismatch conditions — •Eike Köhnen, Marko Jost, Philipp Tockhorn, Anna B. Morales Vilches, Amran Al-Ashouri, Bernd Stannowski, and Steve Albrecht — Helmholtz-Zentrum Berlin, Germany

To well exceed the theoretical efficiency limit for silicon single junction solar cells, multiple absorbers with different bandgaps can be combined into tandem solar cells. Recently, metal halide perovskites have attracted significant scientific attention as tandem partner with silicon. Here, we combine a rear emitter silicon cell with a p-i-n perovskite cell into a highly efficient monolithic tandem cell. With this design, a certified tandem efficiency of 25% is realized at highly unmatched sub-cell photocurrents. Further improvements of the top contact and the perovskite thickness, enabled a remarkably efficiency of 26%, the highest yet published value. Additionally, we show how these tandem solar cells behave under various illumination spectra, e.g. when the sun spectrum changes over the day. Using selective illumination, different mismatch conditions are generated, affecting the tandem fill factor (FF). The experimental findings are reproduced by equivalent circuit simulations based on single cell parametrization. In both experiment and simulation, we find that the FF increases significantly when the sub-cells become more unmatched, an important finding as the FF enhancement slightly compensates the photocurrent reduction due to current mismatch. This will affect the mismatch condition for optimum performance and also affects the energy yield of the tandem solar cell.