Cr–O–In interlocking for window layer delamination resistance in operationally stable perovskite/silicon tandem solar cells

Abstract

Perovskite/silicon tandem solar cells have exhibited remarkable efficiencies but remain limited by poor operational stability, primarily due to the instability of fullerene/atomic-layer-deposited (ALD) SnO_X interfaces in the top window layer – an issue that is often negligible in single-junction devices but becomes critically important in tandems. This instability originates from poor adhesion, incomplete precursor reactions during the low-temperature ALD process, and oxidative exposure of the fullerene layer. Here, we introduce a Cr–O–In interlocking interface formed via chromium (Cr) diffusion into the transparent electrode and fullerene layer, which effectively mitigates window layer delamination and establishes robust interfacial contact. Notably, Cr does not diffuse across the fullerene layer due to its strong reaction with the C₆₀ layer, which effectively immobilizes the metal atoms shortly after deposition and impedes deep diffusion. In addition, this interlocking interface integrates optical transparency, favorable band alignment, and resistance to sputtering, while enabling n-type doping of the fullerene layer to enhance electron mobility and suppress across-interface nonradiative recombination. As a result, single-junction 1.67 eV perovskite solar cells exhibit a PCE of 23.27% (average PCE of 22.85%), and perovskite/silicon tandems exhibit 32.77%, with a certified stabilized efficiency of 32.51%, among the highest reported for monolithic perovskite/TOPCon tandems. Moreover, the Cr–O–In ionic interlocking interface enhances long-term operational stability, paving the way toward scalable, industrially applicable tandem photovoltaics.