Energy Funneling in Quasi‐2D Ruddlesden–Popper Perovskites: Charge Transfer versus Resonant Energy Transfer

The quasi‐2D Ruddlesden–Popper perovskites contain a collection of grains with inhomogeneous bandgaps, enabling efficient energy funneling from high‐bandgap grains (donors) to low‐bandgap grains (acceptors), leading to localization of carriers and suppression of defect trapping. However, the exact mechanism for the energy funneling is still fiercely debated. Charge transfer (CT) via carrier diffusion and Förster resonance energy transfer (FRET) based on dipole interactions are the two conceivable models. Herein, by controlling the degree of energy funneling, both carrier dynamics of donors and acceptors are investigated. Transient absorption (TA) results suggest that the energy funneling mainly occurs at a timescale longer than the FRET mechanism. Moreover, the degree of energy funneling is revealed and the carrier diffusion lengths display a similar dependence on temperature, evidencing the interdomain energy funneling is dominated by CT. This work provides a significant insight into energy funneling mechanism that is important for future developments of optoelectronic devices.