The Role of the Monovalent Cation on the Recombination Kinetics in Lead Iodide Perovskites

Eline Hutter^a, Rebecca Sutton^b, Yinghong Hu^c, Michiel Petrus^c, Pablo Docampo^c^,^d, Samuel Stranks^e, Henry Snaith^b, Tom Savenije^a

^aDelft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands

^bOxford University, Clarendon Laboratory, Department of Physics, Oxford OX1 3PU, Reino Unido, United Kingdom

^cChemistry Department, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München 81377, Germany

^dSchool of Electrical and Electronic Engineering, Newcastle University, Merz court, NE1 7RU, Newcastle upon Tyne, United Kingdom

^eCavendish Laboratory, University of Cambridge - UK, JJ Thomson Avenue, 9, Cambridge, United Kingdom

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)

Benidorm, Spain, 2018 May 28th - 31st

Organizers: Emilio Palomares and Rene Janssen

Oral, Eline Hutter, presentation 062
Publication date: 21st February 2018

Metal halide perovskites such as methylammonium lead iodide (MAPbI₃) are highly promising materials for photovoltaics. However, the relationship between the organic nature of the cation and the optoelectronic quality remains debated. In this work, we use different techniques to prepare fully inorganic black-phase CsPbI₃,¹ and compare the optoelectronic properties to their MA-based analogues.^2,3 Using the Time-Resolved Microwave Conductivity (TRMC) technique, we measure charge carrier mobilities of around 25 cm²/(Vs) in CsPbI₃ prepared via physical vapor deposition,¹ which is very comparable to the 37 cm²/(Vs) that we found in vapor-deposited MAPbI₃.² Furthermore, we observe impressively long charge carrier lifetimes exceeding 10 microseconds for these vapor-deposited CsPbI₃ films and corresponding second order recombination rate constants of 1.3 x 10^-10 cm³s^-1, which is again similar to fully optimized MAPbI₃ layers. Additionally, we find that these high quality CsPbI₃ films yield photovoltaic devices with power conversion efficiencies close to 9%.¹ Altogether, our results suggest that charge carrier mobility and lifetime are mainly dictated by the inorganic framework rather than the organic nature of the cation. However, in spite of its promising optoelectronic properties, fully inorganic CsPbI₃ perovskites suffer from inferior crystal-phase stability and thus, the presence of organic cations might still be required for production of stable, high-efficiency solar cells. On studying a number of mixed-cation perovskites, we finally find that in fact, the charge carrier mobilities and lifetimes are favorably tuned by adding controlled amounts of inorganic cations, such as Cs and Rb, to metal halide perovskites with organic cations.³

1. Hutter, E. M.; Sutton, R. J.; Chandrashekar, S.; Abdi-Jalebi, M.; Stranks, S. D.; Snaith, H. J.; Savenije, T. J. ACS Energy Lett. 2017, 2, 1901.

2. Hutter, E. M.; Hofman, J.-J.; Petrus, M. L.; Moes, M.; Abellón, R. D.; Docampo, P.; Savenije, T. J. Adv. Energy Mater. 2017, 1602349.

3. Hu, Y.; Hutter, E. M.; Rieder, P.; Grill, I.; Hanisch, J.; Aygüler, M. F.; Hufnagel, A. G.; Handloser, M.; Bein, T.; Hartschuh, A.; Tvingstedt, K.; Dyakonov, V.; Baumann, A.; Savenije, T. J.; Petrus, M. L.; Docampo, P. Adv. Energy Mater. 2018, 1703057.

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