Evidence for surface defect passivation as the origin of the remarkable photostability of unencapsulated perovskite solar cells employing aminovaleric acid as a processing additive

This study addresses the cause of enhanced stability of methyl ammonium lead iodide when processed with aminovaleric acid additives (AVA-MAPbI 3 ) in screen printed, hole transport layer free perovskite solar cells with carbon top electrodes (c-PSC). Employing AVA as an additive in the active layer...

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Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019, Vol.7 (7), p.3006-3011
Main Authors: Lin, Chieh-Ting, De Rossi, Francesca, Kim, Jinhyun, Baker, Jenny, Ngiam, Jonathan, Xu, Bob, Pont, Sebastian, Aristidou, Nicholas, Haque, Saif A., Watson, Trystan, McLachlan, Martyn A., Durrant, James R.
Format: Article
Language:English
Subjects:
Acids
Additives
Ammonium
Grain boundaries
Information processing
Iodides
Ion scattering
Ion scattering spectroscopy
Lead
Oxygen
Perovskites
Photobleaching
Photoluminescence
Photons
Photovoltaic cells
Service life assessment
Solar cells
Spectroscopy
Stability
Superoxide
Surface defects
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Summary:This study addresses the cause of enhanced stability of methyl ammonium lead iodide when processed with aminovaleric acid additives (AVA-MAPbI 3 ) in screen printed, hole transport layer free perovskite solar cells with carbon top electrodes (c-PSC). Employing AVA as an additive in the active layer caused a 40-fold increase in device lifetime measured under full sun illumination in ambient air (RH ∼ 15%). This stability improvement with AVA was also observed in optical photobleaching studies of planar films on glass, indicating this improvement is intrinsic to the perovskite film. Employing low-energy ion scattering spectroscopy, photoluminescence studies as a function of AVA and oxygen exposure, and a molecular probe for superoxide generation, we conclude that even though superoxide is generated in both AVA-MAPbI 3 and MAPbI 3 films, AVA located at grain boundaries is able to passivate surface defect sites, resulting in enhanced resistivity to oxygen induced degradation. These results are discussed in terms of their implications for the design of environmentally stable perovskite solar cells.
ISSN:2050-7488
2050-7496
DOI:10.1039/C8TA11985F