Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 72: Hybrid and Perovskite Photovoltaics I

CPP 72.10: Talk

Thursday, March 15, 2018, 17:45–18:00, C 264

Topography-dependent phase-segregation in mixed-halide perovskite — •Xiaofeng Tang, Gebhard Matt, and Christoph Brabec — Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Mixed-halide perovskites have emerged as promising materials for optoelectronics due to the merit of their tunable bandgap in the entire visible region. A challenge remains however in the instability of the bandgap. This bandgap instability is attributed to phase-segregation, which strongly affects the voltage attained in mixed-halide perovskite-based solar cells and seriously restricts the applications.

In this work, we provide an in-depth insight into this phenomenon with a combination of local-resolved and bulk investigations. We demonstrate phase-segregation in mixed-halide perovskite is topography-dependent. By using spatially-resolved photoluminescence spectroscopy, we show the gradual red-shift of the photoluminescence signal at the grain boundaries of mixed-halide perovskite during the consecutive illumination. Contrarily, we observe the spectrally stable emission exclusively stems from the grain centers. Such difference is further evidenced by bulk characterizations, showing the illuminated mixed-halide perovskite presenting double band-edge features. The above spatially selective halide separation provides a strong argument that ion migration indeed dominantly occurs along these boundaries and will support the development of better passivation strategies, ultimately allowing to process environmentally stable perovskite films.