Rear interface engineering to suppress migration of iodide ions for efficient perovskite solar cells with minimized hysteresis

Accurate interface engineering can effectively inhibit iodide ion migration, thereby improving the stability and photovoltaic performance of perovskite solar cells (PvSCs). The time-of-flight secondary-ion mass spectrometry reveals that in an aged n-i-p-type PvSC, the iodide ions will move toward the rear side and enter the FTO cathode. In this regard, the authors describe a simple thermal evaporation strategy for introducing an NdCl${}_3$ interface layer (NdCl${}_3$-IL) at the rear interface of perovskites to interdict the iodine ion migration pathway, leading to reduced trap densities throughout the whole perovskite region. As a result, a boosted open-circuit voltage (V${}_{OC}$) is achieved, resulting in power conversion efficiency (PCE) up to 22.16% with negligible hysteresis. The NdCl${}_3$-IL also enhances the device stability, maintaining 83% of initial PCE after the maximum-power-point tracking test for 100 h. More encouragingly, a certified PCE of 21.68% is demonstrated on a large-area (1 cm${}^2$) device with combined 2D/3D passivation strategies. (© 2021 Wiley‐VCH GmbH)