Influence of FK209 Cobalt Doped Electron Transport Layer in Cesium Based Perovskite Solar Cells.

The efficiency and stability of perovskite solar cells (PSCs) depend not only on the perovskite film quality, but they are also influenced by the charge carriers of both the electron and hole transport layers (ETL and HTL). Doping of the carrier transport layers is considered one of effective technique applied to enhance the efficiency and performance of the PSCs. FK209 cobalt TFSI and lithium TFSI salt were investigated as dopants for mesoporous TiO₂ (M-TiO₂) in the ETL. Herein, FK209 cobalt doping offers improved conductivity, reproducibility and stability compared to other doping or undoped M-TiO₂ control device. It has been found that an optimum concentration of 2.5 mg FK209 cobalt in the M-TiO₂ has resulted in an efficiency of 15.6% on 0.36 cm² active device area, whereas, the undoped M-TiO₂ yielded an average efficiency of 10.8%. The enhanced efficiency is due to the improved conductivity of the ETL while maintaining high transparency and low surface roughness with FK209 doping. The M-TiO₂ doped with FK209 has a transparency of the 90% over the visible range and its measured energy gap was 3.59 eV. Perovskite films deposited on the M-TiO₂ doped with FK209 has also a lower PL intensity indicating faster charge extraction. The measured lifetime of the perovskite films deposited on the optimised M-TiO₂ film was 115.8 ns. [ABSTRACT FROM AUTHOR]