Ionic Mobility and Charge Carriers Recombination Analyzed in Triple Cation Perovskite Solar Cells

In this work, a study of a characterization technique based on open circuit voltage decay is carried out to obtain the recombination resistance of mobile charge carriers and ionic migration in triple cation perovskite solar cells. The devices were fabricated with the structure FTO/TiO2/Cs0.05FA1−XMAXPb(I1−XBrX)3/spiroOMetad/Au. An equivalent circuit, created in Ngspice, was developed adjusting the capacitance and resistance values to fit the experimental open circuit voltage (Voc) decay curves observed. The aim of this study is to associate the perovskite ionic migration with the Voc characteristic time of charge transport in triple cation perovskite solar cells. Thus, an analysis of the open circuit voltage transient behavior was made by taking measurements of the photovoltage as a function of time. The results indicate that the technique shows charge recombination while the device is illuminated. In addition, an enhancement of the recombination resistance when increasing the FA+ concentration was observed. Finally, the transient behavior was associated with MA+, FA+, Cs+ and I− migration, obtaining an ionic mobility in the range between 10−10 to 10−12 cm2 (Vs)−1.