Perovskite-perovskite tandem photovoltaics with optimized bandgaps

TL;DR

This paper reports the development of high-efficiency perovskite-perovskite tandem solar cells with optimized bandgaps, demonstrating record efficiencies and stability for all-perovskite solar technology.

Contribution

It introduces a novel infrared-absorbing 1.2 eV perovskite and demonstrates its integration into tandem cells with high efficiency and stability, advancing all-perovskite solar cell technology.

Findings

Achieved 17.0% efficiency in monolithic tandem cells.

Achieved 20.3% efficiency in mechanically stacked tandem cells.

Infrared absorbing perovskite shows excellent thermal and atmospheric stability.

Abstract

We demonstrate four and two-terminal perovskite-perovskite tandem solar cells with ideally matched bandgaps. We develop an infrared absorbing 1.2eV bandgap perovskite, $FA_{0.75}Cs_{0.25}Sn_{0.5}Pb_{0.5}I_3$, that can deliver 14.8 % efficiency. By combining this material with a wider bandgap $FA_{0.83}Cs_{0.17}Pb(I_{0.5}Br_{0.5})_3$ material, we reach monolithic two terminal tandem efficiencies of 17.0 % with over 1.65 volts open-circuit voltage. We also make mechanically stacked four terminal tandem cells and obtain 20.3 % efficiency. Crucially, we find that our infrared absorbing perovskite cells exhibit excellent thermal and atmospheric stability, unprecedented for Sn based perovskites. This device architecture and materials set will enable 'all perovskite' thin film solar cells to reach the highest efficiencies in the long term at the lowest costs.