Operando Charge Carrier Dynamics by Intensity-Modulated Photoluminescence: From Perovskite Thin Films to Solar Cells
The charge-carrier lifetime in halide perovskites often varies by orders of magnitude with the injection level, complicating the analysis of conventional time-resolved photoluminescence and comparisons of reported lifetimes. We use intensity-modulated photoluminescence spectroscopy (IMPLS) as a frequency-domain alternative. Carried out under operating conditions, it yields the lifetime at a specific injection level, e.g., one-sun-equivalent illumination. On thin films, IMPLS and steady-state photoluminescence yield comparable lifetimes. For perovskite/transport-layer stacks, the IMPLS response becomes more complex. A dedicated transfer function disentangles charge transfer from interface recombination and predicts an upper limit on the charge-carrier lifetime in the solar cell. In devices, electrical methods such as intensity-modulated photovoltage spectroscopy (IMVS) often fail to measure the lifetime due to capacitive effects. IMPLS shows not only the same two characteristic frequencies as IMVS, but also a third one, thereby resolving the lifetime itself.