Abstract

Organic-inorganic halide perovskites have rapidly grown as favorable materials for photovoltaic applications, but accomplishing long-term stability is still a major research problem. This work demonstrates a new insight on instability and degradation factors in CH3NH3PbI3 perovskite solar cells aging with time in open air. X-ray photoelectron spectroscopy (XPS) has been used to investigate the compositional changes caused by device degradation over the period of 1000 hrs. XPS spectra confirm the migration of metallic ions from the bottom electrode (ITO) as a key factor causing the chemical composition change in the perovskite layer besides the diffusion of oxygen. XPS results are in good agreement with the crystallographic marks. Glow discharge optical emission spectrometry (GD-OES) has also been performed on the samples to correlate the XPS results. Based on the experimental results, fundamental features that account for the instability in the perovskite solar cell is discussed.

Highlights

  • Chemical instability of organic-inorganic hybrid lead halide perovskites limits their performance and durability in various applications such as solar cells[1,2], photo-assisted water splitting[3,4], solid-oxide fuel cells[5,6] etc

  • Typical Perovskite solar cell structures consist of indium tin oxide (ITO)/ fluorine doped tin oxide (FTO), TiO2 layers followed by the perovskite layer, hole transport layer and the top metal electrode

  • We have found that the elemental migration and chemical changes due to oxygen element could be among the major factors that cause instability in CH3NH3PbI3 perovskite solar cells

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Summary

Introduction

Chemical instability of organic-inorganic hybrid lead halide perovskites limits their performance and durability in various applications such as solar cells[1,2], photo-assisted water splitting[3,4], solid-oxide fuel cells[5,6] etc. Even though the progress of perovskite solar cells (PSCs) has gone from operating under unstable liquid electrolytes far to solid state hole-transporting materials (HTMs)[7], a proper understanding of degradation mechanisms for perovskite materials and their relevant solutions still need to be explored. Nazeeruddin’s group synthesized molecularly engineered novel dopant-free star-shaped D-π-A type hole transporting materials, which in combination with mixed-perovskite (FAPbI3)0.85(MAPbBr3)0.15 (MA: CH3NH3+, FA: NH = CHNH3+) exhibit an excellent power conversion efficiency (PCE) of 18.9% under AM 1.5 conditions. Typical Perovskite solar cell structures consist of indium tin oxide (ITO)/ fluorine doped tin oxide (FTO), TiO2 (compact and mesoporous) layers followed by the perovskite layer, hole transport layer and the top metal electrode. We have found that the elemental migration and chemical changes due to oxygen element could be among the major factors that cause instability in CH3NH3PbI3 perovskite solar cells

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Conclusion

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