Study on the Al–P3HT:PCBM interfaces in electrical stressed polymer solar cell by X-ray photoelectron spectroscopy

• The electrical field stress enhances the fill factor, short-circuits current and power conversion efficiency of the polymer solar cell.
• XPS depth profile confirmed the penetration and oxidation of Al into the polymer layer under a large electrical field.
• The oxidation of Al related to formation of an AlOC moiety confirmed by Al 2p and C1s signal.

In this study, X-ray photoelectron spectroscopy (XPS) was used to investigate the metal–organic interfaces of a P3HT:PCBM bulk-heterojunction (BHJ) organic solar cell under a high electrical field. This high electrical field was built by applying reverse bias to the solar cell. This electrical field stress enhances the fill factor, short-circuits current and reduces series resistance. As a consequence, the power conversion efficiency of a polymer solar cell enhanced by 8.3% compared to an unstressed solar cell. In addition, the reverse current density was quite low, consumed only a small amount of energy (0.36 mJ/cm2) during stressing. The intermixing and atomic concentration gradient of Al and C shown by an XPS depth profile confirmed the penetration of Al into the polymer layer under a large electrical field, which improved the contact properties.

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