Air stable CsPbIBr2 films for efficient indoor photovoltaics
Paheli Ghosh a, Jochen Bruckbauer b, Carol Trager-Cowan b, Lethy Krishnan Jagadamma a
a SUPA, School of Physics & Astronomy, University of St Andrews, Physical Science Building, North Haugh, University of St Andrews, St. Andrews, KY16 9SS, United Kingdom
b Department of Physics, University of Strathclyde, Glasgow, United Kingdom
Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)
Online, Spain, 2021 May 24th - 28th
Organizers: Marina Freitag, Feng Gao and Sam Stranks
Poster, Paheli Ghosh, 174
Publication date: 11th May 2021

Research on indoor photovoltaic (IPV) devices is currently generating immense interest due to the prospects of powering ‘smart’ electronics in the Internet of Things (IoT). Inorganic halide perovskites using Cs+ as the A-site cation have demonstrated impressive long-term stability at high temperature and also have a tunable bandgap ranging from 1.73 to 2.3 eV [1], [2]. Research on inorganic Cs-based perovskite solar cells (PSCs) have been primarily focussed on optimal 1 Sun performance, but the recent explosion in IoT has necessitated the investigation of PV device performance under indoor light illumination, for which CsPbIBr2 is an ideal choice due to its wide bandgap. However, the lack of air stability, high hysteresis in J-V curves, and high processing temperature have limited the wide application of this promising semiconductor.

In this study, it is shown that all-inorganic Cs-based halide perovskites are promising for indoor light harvesting due to their wide bandgap matched to the indoor light spectra. The selection of anti-solvent was found to be critical in obtaining the desired morphology and improving the air-stability of CsPbIBr2 films. X-ray photoelectron spectroscopy revealed that anti-solvent treatment with the appropriate solvents is effective in reducing the defect density in the form of metallic Pb. Furthermore, electron backscattered diffraction revealed that grain misorientation is also reduced. A pinhole-free CsPbIBr2/Spiro-OMeTAD interface can preserve the perovskite α phase and enhance the air-stability of the devices. Highly crystalline and compact CsPbIBr2 perovskite-based devices demonstrated a power conversion efficiency (PCE) of 14.1% under indoor lighting conditions. Such devices retained >55% of the maximum PCE after storage under 30% relative humidity for a shelf life duration of 40 days which is one of the best reported so far for CsPbIBr2 films. These low temperature-processed, efficient, and air-stable CsPbIBr2 perovskite photovoltaic devices show the promise of compatibility with flexible and wearable substrates for powering next-generation electronic devices in the IoT.

[1]     J. Zhang, G. Hodes, Z. Jin, and S. Liu, “All-Inorganic CsPbX3 Perovskite Solar Cells: Progress and Prospects,” Angew. Chemie - Int. Ed., vol. 58, no. 44, pp. 15596–15618, 2019.

[2]     W. Xiang and W. Tress, “Review on Recent Progress of All-Inorganic Metal Halide Perovskites and Solar Cells,” Adv. Mater., vol. 31, p. 1902851, 2019.

LKJ acknowledges funding from UKRI-FLF through MR/T022094/1. LKJ and PG acknowledge Dr Ben F. Spencer for the XPS data acquisition which was supported by the Henry Royce Institute, funded through UK EPSRC grants EP/R00661X/1, EP/P025021/1 and EP/P025498/1. LKJ and PG acknowledge Professor Ifor D. W. Samuel and Professor Graham A. Turnbull for the kind permission to access some of the research facilities and Dr Julia L. Payne for the help with XRD and FTIR measurements. JB and CTC acknowledge funding from UK EPSRC grant EP/P015719/1.

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