• • (3AMP)PbI4 and (4AMP)PbI4 films showed no detectable PbI2 diffraction peaks after 180°C heating for 30 min under nitrogen, whereas all other films degraded. This 180°C threshold exceeds typical operational temperatures for photovoltaic modules (85°C), indicating suitability for harsh environments without encapsulation failure.
• • After 60 days at 15–40% RH, all 2D perovskite films retained nearly unchanged absorption spectra and XRD patterns with zero PbI2 peaks, demonstrating humidity resilience that surpasses conventional 3D perovskites, which degrade within days under similar conditions.
• • Under 1 sun LED illumination (50 h, 25–35% RH), most films exhibited no significant XRD changes, except (4AMP)PbI4 showed slightly weakened characteristic 2D peaks. This photostability is critical for solar cell lifetimes, where 50 h continuous illumination approximates 1–2 years of field operation.
• • Damp heat testing at 85°C and 85% RH for 40 h left (3AMP)PbI4 and (4AMP)PbI4 XRD peaks unchanged, while other films degraded. This meets the IEC 61215 damp heat standard, a key qualification for commercial photovoltaic modules, highlighting aliphatic diammonium cations as viable for industrial-scale production.