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Traditional inorganic semiconductors can be electronically doped with high precision. Conversely, there is still conjecture regarding the assessment of the electronic doping density in metal-halide perovskites, not to mention of a control thereof. This paper presents a multifaceted approach to determine the electronic doping density for a range of different lead-halide perovskite systems. Optical and electrical characterization techniques, comprising intensity-dependent and transient photoluminescence, AC Hall effect, transfer-length-methods, and charge extraction measurements were instrumental in quantifying an upper limit for the doping density. The obtained values are subsequently compared to the electrode charge per cell volume under short-circuit conditions (C U bi / e V), which amounts to roughly 1016 cm−3. This figure of merit represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results consistently demonstrate that the doping density is below this critical threshold (∼1012 cm−3, which means ≪ C U bi / e V) for all common lead-based metal-halide perovskites. Nevertheless, although the density of doping-induced charges is too low to redistribute the built-in voltage in the perovskite active layer, mobile ions are present in sufficient quantities to create space-charge-regions in the active layer, reminiscent of doped pn-junctions. These results are well supported by drift–diffusion simulations, which confirm that the device performance is not affected by such low doping densities. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Efficient mixed metal lead‐tin halide perovskites are essential for the development of all‐perovskite tandem solar cells, however they are currently limited by significant short‐circuit current losses despite their near optimal bandgap (≈1.25 eV). Herein, the origin of these losses is investigated, using a combination of voltage dependent photoluminescence (PL) timeseries and various charge extraction measurements. It is demonstrated that the Pb/Sn‐perovskite devices suffer from a reduction in the charge extraction efficiency within the first few seconds of operation, which leads to a loss in current and lower maximum power output. In addition, the emitted PL from the device rises on the exact same timescales due to the accumulation of electronic charges in the active layer. Using transient charge extraction measurements, it is shown that these observations cannot be explained by doping‐induced electronic charges but by the movement of mobile ions toward the perovskite/transport layer interfaces, which inhibits charge extraction due to band flattening. Finally, these findings are generalized to lead‐based perovskites, showing that the loss mechanism is universal. This elucidates the negative role mobile ions play in perovskite solar cells and paves a path toward understanding and mitigating a key loss mechanism. [ABSTRACT FROM AUTHOR]