High-efficiency and UV-stable flexible perovskite solar cells enabled by an alkaloid-doped C60 electron transport layer†
The inferior stability of perovskite solar cells (PSCs) under ultraviolet (UV) irradiation has been a bottleneck for their further commercialization. Herein, we report a simple strategy to enhance the UV stability of PSCs by using an alkaloid 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) doped C60 electron transport layer (ETL). By improving the electron mobility of ETLs to 2 cm2 V−1 s−1 and optimizing the conduction band position to 4.2 eV, the DBU-doped C60 (DBU-C60) ETLs enable the rigid and flexible planner n-i-p PSCs to exhibit PCEs of 20% and 16%, respectively. Most importantly, the devices based on the DBU-C60 ETLs retain over 80% of their initial efficiency after storage either under UV irradiation for 336 h or light socking for 1000 h in an ambient environment. These results indicate that the optimized C60 is a promising electron transport material to stabilize the PSCs under UV light illumination without the cost of efficiency loss.