Intensity-Modulated Photoluminescence Spectroscopy for Revealing Ionic Processes in Halide Perovskites

High Resolution Image Download MS PowerPoint Slide Mobile ions limit halide perovskite device performance, yet quantifying ionic properties remains challenging. Frequency-domain electrical techniques are restricted to operational devices, and the resulting signals are often dominated by interfacial recombination which obscures ionic contributions. Here, we introduce intensity-modulated photoluminescence spectroscopy (IMPLS) as a fully optical alternative, where the amplitude and phase of the photoluminescence intensity is measured as a function of excitation modulation frequency. IMPLS is demonstrated on a Cs 0.07 (FA 0.83 MA 0.17 ) 0.93 Pb(I 0.83 Br 0.17 ) 3 film. Fitting the data with an optical equivalent circuit model reveals two characteristic lifetimes: τ char = 2.1 ms and 77 s, likely corresponding to defect formation and ionic diffusion, respectively. The diffusion feature is consistent with intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) measurements on corresponding full devices. Importantly, IMPLS enables contact-free characterization of slow processes for all perovskite sample types, including films and devices, significantly expanding the techniques available for understanding mobile ions in these materials.