Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Segregation of illuminated mixed-halide perovskites into iodide- and bromide-rich domains presents a critical bottleneck in the application of wide-bandgap absorbers in single- and multi-junction architectures. And while its occurrence has been well-studied in thin films, the influence on operational solar cells lacks sufficient understanding.
This work employs a multimodal characterization procedure to observe the slow progression of halide segregation in efficient solar cells prepared in the p-i-n architecture using sequentially processed perovskite absorbers. Photoluminescence spectroscopy is used to identify the stages that demixing of halide ions entails while simultaneous tracking of photovoltaic parameters allows correlating performance degradation to the migration of ionic species in each stage. A new stage of the process is thus observed upon prolonged illumination. Characterization of sub-bandgap features reveals the occurrence of photo-induced defect formation whose suppression through cationic substitution provides a strategy for stabilization of wide-bandgap compositions against halide segregation.