Room-Temperature-Processed Fullerene/TiO_2 Nanocomposite Electron Transporting Layer for High- Efficiency Rigid and Flexible Planar Perovskite Solar Cells

摘要

Room-temperature-processed TiO_2 (R-Lt-TiO_2) electron transporting layers (ETLs) possess low conductivity and connectivity, resulting in poor photovoltaic performance. Herein, an ethanol (EtOH)-soluble, highly conducting fullerene derivative, C_(60)RT_6, was used as an additive for Lt-TiO_2 ETLs. Room-temperature processed nanocomposite ETL (R-Fu/Lt-TiO_2) is prepared simply by spin coating a C_(60)RT_6 and G-TiO_2 NPs (TiO_2 nanoparticle prepared by grinding the bulk TiO_2 powder) mixture. R-Fu/Lt-TiO_2 has better aligned with the frontier orbitals of the FA_xMA_(1-x)PbI_3, better continuity, conductivity, flatness, and higher surface hydrophilicity compared to Lt-TiO_2 ETL. Perovskite films spin coated on R-Fu/ Lt-TiO_2 ETLs also have slightly larger grains and thickness compared to those deposited on Lt-TiO_2. Perovskite solar cells (PSCs) based on a R-Fu/Lt-TiO_2 ETL possess higher power conversion efficiency (PCE, up to 20% on glass substrate), less (negligible) current hysteresis, and better long-term stability compared to those using R-Lt-TiO_2 as an ETL. The flexible PSC (used indium tin oxide/ polyethylene terephthalate (ITO/PET) as a substrate) with a R-Fu/Lt-TiO_2 ETL achieves a PCE of 18.06% and retains 90% of the initial PCE after 500 bending cycles with a bending radius of 6 mm. The PCE of the flexible cell with a Lt-TiO_2 ETL is only 8.2%, and loses 60% of the initial value after 500 bending cycles.