Characterization of Planar Lead Halide Perovskite Solar Cells by Impedance Spectroscopy, Open-Circuit Photovoltage Decay, and Intensity-Modulated Photovoltage/Photocurrent Spectroscopy

Thin film lead halide perovskite cells, where the perovskite layer is deposited directly onto a flat titania blocking layer, have reached AM 1.5 efficiencies of over 15%,1 showing that the mesoporous scaffold used in early types of perovskite solar cells is not essential. We used a variety of techniques to gain a better understanding of thin film perovskite cells prepared by a solution-based method. Twelve cells were studied, which showed AM 1.5 efficiencies of ∼11%. The properties of the cells were investigated using impedance spectroscopy, intensity-modulated photovoltage spectroscopy (IMVS), intensity-modulated photocurrent spectroscopy (IMPS), and open-circuit photovoltage decay (OCVD). Despite the fact that all 12 cells were prepared at the same time under nominally identical conditions, their behavior fell into two distinct groups. One half of the cells exhibited ideality factors of m ≈ 2.5, and the other half showed ideality factors of m ≈ 5. Impedance spectroscopy carried out under illumination at...