Quantification of Efficiency Losses Due to Mobile Ions in Perovskite Solar Cells via Fast Hysteresis Measurements

Abstract

Perovskite semiconductors differ from most inorganic and organic semiconductors due to the presence of mobile ions in the material. Although the phenomenon is intensively investigated, important questions such as the exact impact of the mobile ions on the steady‐state power conversion efficiency (PCE) and stability remain. Herein, a simple method is proposed to estimate the efficiency loss due to mobile ions via “fast‐hysteresis” measurements by preventing the perturbation of mobile ions out of their equilibrium position at fast scan speeds (1000 V s−1). The “ion‐free” PCE is between 1% and 3% higher than the steady‐state PCE, demonstrating the importance of ion‐induced losses, even in cells with low levels of hysteresis at typical scan speeds (100 mV s−1). The hysteresis over many orders of magnitude in scan speed provides important information on the effective ion diffusion constant from the peak hysteresis position. The fast‐hysteresis measurements are corroborated by transient charge extraction and capacitance measurements and numerical simulations, which confirm the experimental findings and provide important insights into the charge carrier dynamics. The proposed method to quantify PCE losses due to field screening induced by mobile ions clarifies several important experimental observations and opens up a large range of future experiments.

Fill Factor Losses and Deviations from the Superposition Principle in Lead Halide Perovskite Solar Cells

“…Thus, the hysteresis present in actual perovskite solar cells can cause the effect of field screening to change as a function of, for example, scan speed or temperature. [68,69] Figure 5b,d shows the associated dark and illuminated current-voltage curves, whereby the latter are shifted into the first quadrant by adding the respective J sc as described previously. We note that in the case without field screening (Figure 5b), the photoshunt is much less pronounced than in the situation with field screening (Figure 5d).…”

Impact of non-stoichiometry on ion migration and photovoltaic performance of formamidinium-based perovskite solar cells

“…The detrimental effect of ions on the performance of PSCs has recently been analysed by Le Corre et al with results consistent with ours. 53…”

“…The detrimental effect of ions on the performance of PSCs has recently been analysed by Le Corre et al with results consistent with ours. 53 Fig. 8 and 9 show the simulated impedance spectra for different choices of the ionic parameters.…”

Physics, Simulation, and Experiment of Perovskite Solar Cells with Addressing Hysteresis Effect

“…Indeed, adjusting the scan rate of the electric bias is most widely accepted to modify the hysteresis effect. [ 39 ] This is because the ions do not normally respond instantaneously to the change of the external bias due to the low ion mobilities. Figure systematically studies the effects of scan rate on J SC , V OC , PCE, and HI under the ion concentrations of 1 × 10 16 and 1 × 10 17 cm −3 , respectively.…”