Mechanically stacked, two-terminal graphene-based perovskite/silicon tandem solar cell with efficiency over 26%

Perovskite/silicon tandem solar cells represent an attractive pathway to upgrade the market-leading crystalline silicon technology beyond its theoretical limit. Two-terminal architectures result in reduced plant costs compared to four-terminal ones. However, it is challenging to monolithically process perovskite solar cells directly onto the micrometer-sized texturing on the front surface of record-high efficiency amorphous/crystalline silicon heterojunction cells, which limits both high-temperature and solution processing of the top cells. To tackle these hurdles, we present a mechanically stacked two-terminal perovskite/silicon tandem solar cell, with the sub-cells independently fabricated, optimized, and subsequently coupled by contacting the back electrode of the mesoscopic perovskite top cell with the texturized and metalized front contact of the silicon bottom cell. By minimizing optical losses, as achieved by engineering the hole selective layer/rear contact structure, and using a graphene-doped mesoporous electron selective layer for the perovskite top cell, the champion tandem device demonstrates a 26.3% efficiency (25.9% stabilized) over an active area of 1.43 cm2.