Impact of perovskite subcell breakdown on the performance of perovskite/perovskite/silicon triple-junction solar cells

Perovskite-based triple-junction solar cells have recently gained significant attention and are rapidly developing, thanks to the insights gained from the advancement in its dual-junction counterparts. However, employing perovskite materials in multijunction solar cells with more than two junctions brings new challenges that have not yet been addressed. One aspect is the possibility of reverse bias breakdown of perovskite subcells during operation of the triple-junction device. This is more relevant for triple-junction solar cells because a higher reverse voltage might drop at perovskite subcells compared to the case of dual-junction solar cells. Herein, the breakdown voltages of the two perovskite subcells in perovskite/perovskite/silicon triple-junction solar cells are determined by progressively increasing the reverse bias applied to the subcells in a single-junction architecture during current-voltage measurements and monitoring the appearance of shunts using illuminated lock-in thermography measurements. Furthermore, to analyze the effect on the final triple-junction solar cell, the triple-junction device is brought in different current limitation conditions. It is shown that the subcell breakdown can happen during the operation of the triple-junction solar cell, especially for the case where the perovskite top cell is limiting the overall current of the device. This effect is less severe when the middle perovskite cell limits the current due to the absence of a direct contact with the silver metallization which has shown to be the major degradation site during reverse biasing of perovskite solar cells. Finally, there is no concern regarding breakdown of the silicon bottom cell due to the higher breakdown voltage of silicon compared to perovskite.