Mitigation of Vacuum and Illumination-Induced Degradation in Perovskite Solar Cells by Structure Engineering

High specific power, high stowed packing efficiency, low processing cost, and high tolerance against environmental threats (high energy and charged particle radiation) make perovskite solar cell (PSC) a promising candidate for power generation in space. However, vacuum, as encountered in space, causes perovskite outgassing, raising concern for its long-term stability. In this work, we find that PSCs (ITO/SnO₂/perovskite/Spiro-MeOTAD/Au) degrade ten times faster upon reducing the pressure from 9 × 10⁴ to 5 × 10³ Pa during operation, due to acceleration of the perovskite transformation and ion migration. Gas permeability of the layers atop perovskite and mobile ion-induced chemical reactions at charge transporting layers and related interfaces are two critical factors. We develop a PSC structure (ITO/PTAA/perovskite/PCBM/ZnO/AZO/[Ni/Al grid]) that effectively mitigates vacuum and illumination-induced degradation pathways, enabling PSCs to realize a low PCE loss rate of 0.007%/h over 1,037 h at the maximum power point under 100 mW cm⁻² illumination at 5 × 10³ Pa. Organic-inorganic hybrid perovskite (OHP) solar cells have attracted wide attention for space applications since 2017. However, OHP slowly decomposes by outgassing under vacuum as encountered in space, raising concern for its long-term stability. Here, we show that OHP solar cells (ITO/SnO₂/perovskite/Spiro-MeOTAD/Au) degrade ten times faster upon reducing the operating pressure from 900 to 50 mbar. Vacuum accelerates illumination-induced OHP decomposition, accompanied by outgassing and defect formation, which further accelerates ion migration (Li⁺, Au, I⁻, and Br⁻) across the device. We propose an OHP solar cell structure, i.e., ITO/PTAA/OHP/PCBM/ZnO/AZO/(Ni/Al grid), that can effectively minimize outgassing of OHP and avoid accumulation of the mobile ions at charge transporting layers and related interfaces, resulting in a 588-fold operational stability improvement. This work opens new avenues for engineering OHP solar cells against the hard vacuum in the space environment. This work shows that vacuum decreases operational lifetime of perovskite solar cells (ITO/SnO₂/perovskite/Spiro-MeOTAD/Au) by accelerating perovskite decomposition starting from the grain boundaries, accompanied by outgassing and defect formation. These defects further accelerate ion migration (Li⁺, Au⁺ and/or Au³⁺, I⁻, and Br⁻) across the device. We propose a robust perovskite solar cell structure (ITO/PTAA/perovskite/PCBM/ZnO/AZO/[Ni/Al grid]) that effectively mitigates these degradation pathways, leading to a device showing a projected T₈₀ lifetime of 4,750 h at its maximum power point condition, 1-sun illumination at 50 mbar.