Maximizing and stabilizing luminescence from halide perovskites with potassium passivation
Authors: Stefania Cacovich
Mejd Alsari
Giorgio Divitini
Edward P Booker
Samuel D Stranks
Camille Stavrakas
Johannes M Richter
Håkan Rensmo
Mojtaba Abdi-Jalebi
Zahra Andaji-Garmaroudi
Samuele Lilliu
Tom J Savenije
Richard H Friend
Andrew J Pearson
Eline M Hutter
Caterina Ducati
Bertrand Philippe
Journal: Nature (2018)
Discipline: Multidisciplinary
Keywords: Metal halide perovskites; optoelectronic applications; bandgap tuning; luminescence yields; non-radiative losses
Affiliations: Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK., Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK., Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden., Department of Chemical Engineering, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands., Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK., The UAE Centre for Crystallography, United Arab Emirates.

Abstract:  Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications. 

Retracted: No

PubPeer comments:
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 To add to the confusion, rats make an appearance in Figure 4. Fig. 4. Histological images of organ sections as stained by H E (40u00d7) in: (I) liver; (II) intestine; (III) kidney; (IV) spleen. Normal structures are seen in A, B, and C groups, while mild changes without any damages are visible in D group organs cleared by arrows and stars. **Rat groups, A, B, C and D**, were administered standard diet plus different levels of Bio-Fe(II)NPs, 0, 200. 400 and 800 u03bcg mLu2212 1, respectively. ![file] ,