Enhanced Efficiency and Stability in Blade-Coated Perovskite Solar Cells through Using 2,3,4,5,6-Pentafluorophenylethylammonium Halide Additives

The power conversion efficiency (PCE) of perovskite solar cells is sensitive to their method of fabrication as well as the combination of materials in the perovskite layer. Air knife-assisted blade coating enables good quality perovskite films to be formed but the device efficiencies still tend to lag behind those fabricated using spin-coated perovskite layers. Herein we report the use of three 2,3,4,5,6-pentafluorophenylethylammonium halides (FEAX, where X = I–, Br– or Cl–) as additives in nitrogen knife-assisted blade-coated methylammonium lead iodide (MAPbI3) perovskite solar cells. The additives were all found to passivate defects in the MAPbI3 films. The use of chloride as the counteranion led to additive containing films with the largest crystal size and fewest defects and consequently the FEACl film was found to have the highest photoluminescence (PL) intensity, longest average PL lifetime and lowest trap density. These features led to the devices having a high open-circuit voltage (Voc) of 1.17 V and a PCE of 21.4%. In addition, the hydrophobic fluorinated cations led to the additive containing devices being more stable, with those containing FEACl having the best thermal stability and performance under maximum-power-point (MPP) tracking in a humid (≈65%) environment at 50 ± 1 °C.