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. Perovskite/silicon tandem solar cells promise to push the market-leading crystalline silicon technology beyond its theoretical limit while maintaining low fabrication costs. The possibility to fabricate the perovskite top cell by low-cost solution processing may decrease the levelized cost of energy of photovoltaics toward the grid-parity milestone. However, the solution processing of perovskite solar cells directly onto the textured front surface of high-efficiency amorphous/crystalline silicon heterojunction cells is the main bottleneck. Our simple two-terminal mechanical stacking of the sub-cells helps achieve highly performant PV devices. Its crucial advantage is the possibility to fabricate each sub-cell independently before coupling them. Prospectively, performance improvements and upscaling of perovskite solar cells, as well as the background knowledge on electronic component bonding method, make our results relevant to drive economically feasible perovskite/silicon tandem PVs. A novel configuration for high-performant perovskite/silicon tandem solar cells is demonstrated using a facile mechanical stacking of the sub-cells. The resulting champion perovskite/silicon tandem solar cell exhibits a stabilized efficiency of 25.9% over an active area of 1.43 cm2.