Effective Suppression of Cu+-Migration Assisted Degradation in Perovskite Solar Cells with Cu2O as the Hole Transport Layer.

Abstract

Formamidinium-based double-cation perovskite solar cells exhibit rapid performance degradation when the Cu2O hole transport layer is in direct contact with the perovskite. This degradation is attributed to Cu+ migration into the perovskite lattice, causing structural distortion and the formation of CuI and PbI2. X-ray photoelectron spectroscopy detects Cu+ ions even at the antipodal surface of the perovskite, indicating long-range diffusion of the Cu+ ions, probably through grain-boundary migration. To suppress this, a thin film of benzotriazole is introduced at the Cu2O/perovskite interface as a diffusion-blocking layer that also provides mild surface passivation. Adding poly(acrylonitrile-co-methyl acrylate) to the perovskite synthesis solution passivates the grain boundaries and further prevents the migration of Cu+ towards the perovskite. These modifications effectively curb Cu+ migration and its reaction with the perovskite. Consequently, p-i-n perovskite solar cells with the architecture ITO/Cu2O/perovskite/C60/BCP/Ag, incorporating both modifications, exhibit a significant improvement in power conversion efficiency, from ≈4.7 to 14.4%.

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