Overcoming stability limitations of efficient, flexible perovskite solar modules

Despite the remarkable growth of perovskite photovoltaic technology, the performance and stability of flexible perovskite solar modules (f-PSMs) are still below the commercial level, and even the clear reasons for this have hardly been elucidated. Here, we found that flexible perovskite solar cells (f-PSCs) suffer from a trade-off between efficiency and stability due to the off-balance between surface coverage and the charge-transporting property when conventionally using colloidal SnO2 nanoparticles as an electron-transport layer (ETL). To resolve this trade-off, we newly designed an ETL that enhances the charge transport properties and mitigates the shunt sites, resulting in improved efficiency and operational stability. Therefore, we succeeded in achieving a certified efficiency of 21.8% in f-PSC (22.92% in-house) and 16.4% in f-PSM (900 cm2). Furthermore, we discovered that incomplete coverage gives rise to the formation of a shunt pathway, causing the current crowding effect, which could have a significant impact on long-term operational stability.