The Journal of Physical Chemistry Letters 2015-07-16

Perovskite Solar Cells with Large-Area CVD-Graphene for Tandem Solar Cells.

Felix Lang, Marc A Gluba, Steve Albrecht, Jörg Rappich, Lars Korte, Bernd Rech, Norbert H Nickel

Index: J. Phys. Chem. Lett. 6 , 2745-50, (2015)

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Abstract

Perovskite solar cells with transparent contacts may be used to compensate for thermalization losses of silicon solar cells in tandem devices. This offers a way to outreach stagnating efficiencies. However, perovskite top cells in tandem structures require contact layers with high electrical conductivity and optimal transparency. We address this challenge by implementing large-area graphene grown by chemical vapor deposition as a highly transparent electrode in perovskite solar cells, leading to identical charge collection efficiencies. Electrical performance of solar cells with a graphene-based contact reached those of solar cells with standard gold contacts. The optical transmission by far exceeds that of reference devices and amounts to 64.3% below the perovskite band gap. Finally, we demonstrate a four-terminal tandem device combining a high band gap graphene-contacted perovskite top solar cell (Eg = 1.6 eV) with an amorphous/crystalline silicon bottom solar cell (Eg = 1.12 eV).