Synergistic interface layer optimization and surface passivation with fluorocarbon molecules toward efficient and stable inverted planar perovskite solar cells

Large-size organic halide passivation has been considered an efficient approach to enhance the perovskite solar cell (PSC) efficiency and stability. Herein, a facile posttreatment strategy was demonstrated, wherein trifluoromethyl-phenethylamine hydrobromide (CF₃-PEABr) is firstly used to passivate the perovskite film surface. The CF₃-PEABr surface posttreatment could coordinate with halide dangling bonds that exist at the perovskite crystal surface. Moreover, the surface treatment with CF₃-PEABr could efficiently passivate the defects in the perovskite film and suppress the nonradiative carrier recombination. As a result, a high efficiency of 21.3% is obtained, and an increment of 80 mV in V_oc (a large V_oc of 1.15 V, with a 0.42 V voltage deficit) occurs, compared to the control device. To relieve the hydrophobic nature properties of the -CF₃ functional group and the dewetting problem of PCBM layer deposition, a surfactant Triton X-100 is used to modify the PCBM layer. Furthermore, the devices with CF₃-PEABr posttreatment exhibit better operational, thermal (85^°C), and long storage stabilities without any encapsulation.