Revealing the Doping Density in Perovskite Solar Cells and Its Impact on Device Performance
Francisco Peña-Camargo a, Jarla Thiesbrummel a b, Hannes Hempel c, Artem Musiienko d, Vincent M. Le Corre a e, Jonas Diekmann a, Jonathan Warby a, Thomas Unold c, Felix Lang a, Dieter Neher a, Martin Stolterfoht a
a Universität Potsdam, Soft Matter Physics, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany
b Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
c Department of Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109, Berlin, Germany
d Institut für Silizium-Photovoltaik, Helmholtz-Zentrum Berlin für Materialien und Energie, Kekuléstrasse 5, 12489, Berlin, Germany
e Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058, Erlangen, Germany
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Francisco Peña-Camargo, presentation 107
Publication date: 20th April 2022

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 characterisation 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 charge on the electrodes per unit volume at short-circuit conditions, which amounts to roughly 1016 cm-3. This figure equals the product of the capacitance C  and the built-in potential Vbi  and represents the critical limit below which doping-induced charges do not influence the device performance. The experimental results demonstrate consistently that the doping density is below this critical threshold (< 1012 cm-3 which means < CVbi  per unit volume) 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.

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