Stability of Perovskite and Two Terminal Si/perovskite Tandem Solar Cells under Reverse Bias
Ricardo Razera a c, Peter Fiala a, Fan Fu a, Florent Sahli a, Terry Yang a, Matthias Bräuninger a, Henri Boudinov c, Quentin Jeangros a, Christophe Ballif a b
a Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Lausanne, Switzerland
b Swiss Center for Electronics and Microtechnology (CSEM), PV Center, Rue Jaquet-Droz 1, 2000 Neuchâtel, Switzerland
c Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500. Room: M215, 43.133, Porto Alegre, 91501
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Ricardo Razera, presentation 148
Publication date: 11th February 2019

A well-known module reliability issue in crystalline-silicon photovoltaics arises when a shaded cell is driven into reverse bias by illuminated cells connected in series [1]. In this case, the shaded cell may dissipate a substantial amount of power, which can create hot spots and irreversibly damage the cell or encapsulant. This problem is even more severe for perovskite solar cells. It has been demonstrated [2] that, even in the absence of hot spot formation, such cells can degrade simply from being subjected to a few minutes of reverse bias. This degradation was suggested to be caused by an electrochemical reaction that occurs between mobile ions inside the perovskite and the adjacent layers, although only indirect evidence was given [2]. It also remains to be analyzed how the problem may manifest itself in monolithic perovskite/c-Si tandem cells, particularly when illuminated by different spectra and intensities. Here we investigate this instability further by using microstructural analysis techniques to determine the distribution of ions in degraded cells with different compositions and with different contact layers, both in single-junction and in tandem structures. We also analyze the requirements the cell must meet to be considered stable under reverse bias, taking into account the possibility of adding bypass diodes to the module.

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