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Elemental Mapping of Perovskite Solar Cells by Using Multivariate Analysis: An Insight into Degradation Processes.

Accepted version
Peer-reviewed

Type

Article

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Authors

Cacovich, Stefania 
Ireland, Christopher 
Matteocci, Fabio 
Di Carlo, Aldo 

Abstract

The technology of perovskite-based solar cells is evolving rapidly, reaching certified power conversion efficiency values now exceeding 20 %. One of the main drawbacks hindering progress in the field is the long-term stability of the cells: the mixed halide perovskites used in most devices are sensitive to humidity and degrade on a timescale varying from hours to weeks. The degradation mechanisms are poorly understood, but likely arise from combined physical and chemical modifications at the nanometer scale. The characterization of pristine and degraded materials is difficult owing to their complex chemical and physical structure and their relatively poor stability. In this work, we investigated the changes in local composition and morphology of a standard device after 2 months of air exposure in the dark, using scanning transmission electron microscopy (STEM) with nanometer resolution for imaging and analysis. Because of a state-of-the-art technique that combines STEM and energy dispersive X-ray spectroscopy (EDX), and the use of different decomposition algorithms for multivariate analysis, we highlighted the migration of elements across the interfaces between the layers comprising the device. We also noticed a morphological degradation of the hole-transporting layer (HTL), representing one of the main factors enabling the infiltration of moisture in the device, which results in reduced performance.

Description

Keywords

charge transport, electron microscopy, perovskites, solar cells, stability, Calcium Compounds, Electric Power Supplies, Multivariate Analysis, Oxides, Solar Energy, Titanium

Journal Title

ChemSusChem

Conference Name

Journal ISSN

1864-5631
1864-564X

Volume Title

9

Publisher

Wiley
Sponsorship
European Research Council (259619)
European Commission (312483)
S.C., G.D., C.I., and C.D. acknowledge funding from the ERC under grant number 259619 PHOTO EM. C.D. acknowledges financial support from the EU under grant number 312483 ESTEEM2. F.M. and A.D.C. acknowledge funding from the “Polo Solare Organico” Regione Lazio, the “DSSCX” MIURPRIN2010, FP7 ITN “Destiny”, the European Union′s Horizon 2020 framework program for research and innovation under grant agreement No. 653296 (CHEOPS) and the Italian Ministry of Economic Development in the framework of the Operating Agreement with ENEA for Research on the Electric System. S.C. and G.D. thank Dr. Francisco de la Peña and Dr. Pierre Burdet for assistance with PCA analysis.