Mechanisms for light induced degradation in MAPbI3 perovskite thin films and solar cells

Organometal halideperovskites are highly promising materials for photovoltaic applications, yet their rapid degradation remains a significant challenge. Here, the light-inducedstructural degradation mechanism of methylammoniumlead iodide (MAPbI3)perovskitefilms anddevices is studied in low humidity environment usingX-Ray Diffraction, Ultraviolet-Visible (UV-Vis) absorption spectroscopy,Extended X-ray Absorption Fine Structure spectroscopy, Fourier Transform Infrared spectroscopy, anddevice measurements. Under dry conditions, theperovskitefilm degrades only in the presence of both light and oxygen, which together induce the formation of halide anions through donation of electrons to the surrounding oxygen. The halide anions generate free radicals that deprotonate the methylammonium cation and form the highly volatile CH3NH2 molecules that escape and leave pure PbI2 behind. Thedevice findings show that changes in the localstructure at the TiO2 mesoporous layer occur with light, even in the absence of oxygen, and yet such changes can be prevented by the application ofUV blocking layer on the cells. Our results indicate that the stability of mp-TiO2-MAPbI3 photovoltaics can be dramatically improved with effective encapsulation that protects thedevice fromUV light, oxygen, and moisture.

Source: Applied Physics Letters - December 7, 2016 Category: Physics Authors: Ghada Abdelmageed, Leila Jewell, Kaitlin Hellier, Lydia Seymour, Binbin Luo, Frank Bridges, Jin Z. Zhang and Sue Carter Source Type: research