Extracting in Situ Charge Carrier\nDiffusion Parameters in Perovskite Solar Cells with Light Modulated\nTechniques

Frequency\nresolved methods are widely used to determine device\nproperties of perovskite solar cells. However, obtaining the electronic\nparameters for diffusion and recombination by impedance spectroscopy\nhas been so far elusive, since the measured spectra do not present\nthe diffusion of electrons. Here we show that intensity modulated\nphotocurrent spectroscopy (IMPS) displays a high frequency spiraling\nfeature determined by the diffusion-recombination constants, under\nconditions of generation of carriers far from the collecting contact.\nWe present models and experiments in two different configurations:\nthe standard sandwich-contacts solar cell device and the quasi-interdigitated\nback-contact (QIBC) device for lateral long-range diffusion. The results\nof the measurements produce the hole diffusion coefficient of Dp = 0.029 cm2/s\nand lifetime of τp = 16 μs\nfor one cell and Dp =\n0.76 cm2/s and τp = 1.6\nμs for the other. The analysis in the frequency domain is effective\nto separate the carrier diffusion (at high frequency) from the ionic\ncontact phenomena at a low frequency. This result opens the way for\na systematic determination of transport and recombination features\nin a variety of operando conditions.