Elucidating the role of disorder and free-carrier recombination kinetics in CH₃NH₃PbI₃ perovskite films
Apart from broadband absorption of solar radiation, the performance of photovoltaic devices is governed by the density and mobility of photogenerated charge carriers. The latter parameters indicate how many free carriers move away from their origin, and how fast, before loss mechanisms such as carrier recombination occur. However, only lower bounds of these parameters are usually obtained. Here we independently determine both density and mobility of charge carriers in a perovskite film by the use of time-resolved terahertz spectroscopy. Our data reveal the modification of the free carrier response by strong backscattering expected from these heavily disordered perovskite films. The results for different phases and different temperatures show a change of kinetics from two-body recombination at room temperature to three-body recombination at low temperatures. Our results suggest that perovskite-based solar cells can perform well even at low temperatures as long as the three-body recombination has not become predominant.
© 2015 Macmillan Publishers Limited. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received 08 December 2014; Accepted 24 June 2015; Published 30 July 2015. E.E.M.C. acknowledges support from Singapore Ministry of Education AcRF Tier 1 (RG13/12 and RG123/14), and the National Research Foundation Competitive Research Programme (NRF-CRP4-2008-04). R.A.M. thanks the ONR and ARO for their support. M.-E.M.-B. is grateful to the Nanyang Technological University for supporting the Biophysics Center. H.S. wishes to thank the support from A*STAR SERC (Grant no. 1223600006, 1121202012). Y.M.L. acknowledges support from the Danish Council for Strategic Research under the CHASOL project and also BMBF/NTU under the 1°N Programme. Contributions: M.-E.M.-B. and E.E.M.C. conceived the project. C.L. designed the TRTS experiments. C.L., L.C. and H.X. performed the TRTS experiments. C.L., L.C., R.A.M., M.-E.M.-B. and E.E.M.C. analysed the data. M.T.K. and R.H. performed the absorption spectroscopy experiments. T.S., J.K. and Y.M.L. provided the perovskite samples. C.L., R.A.M., M.-E.M.-B. and E.E.M.C. wrote the manuscript. All authors discussed and improved the manuscript. The authors declare no competing financial interests.
Supplemental Material - ncomms8903-s1.pdf
Published - ncomms8903.pdf