Degradation mechanism of organic solar cells with aluminum cathode

Polymer-based solar cells with aluminum (Al) cathode often suffer from degradation in air. Here the study focuses on the degradation mechanism at the interface between Al and organic active layer. By performing interface modification combined with electrical and chemical characterization, it is demonstrated that the rapid degradation originates from the formation of a charge blocking layer between evaporated Al cathode and organic active layer. Insertion of a thin interfacial layer of thermally evaporated CrOx between organic active layer and Al cathode can greatly improve the device stability. It is found that the CrOx interfacial layer functions as a protective layer by stopping or minimizing penetration of thermally evaporated Al into the active layer to form a diffused organic–Al interface, which will then result in a large oxidized interfacial area upon air exposure.

A thin CrOx layer and CrOx–LiF bilayer under Al cathode improve the performance and air stability of organic solar cells.Figure optionsDownload as PowerPoint slideHighlights
► Al–organic interface dominant air-degradation of P3HT:PCBM solar cells studied.
► Degraded Al–organic interface characterized by XPS and impedance spectroscopy.
► An oxide charge-blocking layer formed at Al–organic interface identified.
► Insertion of an ultrathin CrOx layer between Al and active layer suppressed the air degradation.