Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼1018 cm-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs.
|Number of pages||9|
|Journal||ACS Energy Letters|
|Publication status||Published - 2023 Jan 13|
Bibliographical noteFunding Information:
We thank Jaco Geuchies, Maksim Grechko, and Heejae Kim for fruitful discussions and constructive comments. E.D. acknowledges financial support from the Research Foundation - Flanders (FWO Grant No. S002019N) and from the KU Leuven Research Fund (KUL grant No. STG/21/010). J.H. acknowledges financial support from the Research Foundation - Flanders (FWO Grant Nos. G.0B39.15, G.0B49.15, G098319N, S002019N, and ZW15_09-GOH6316), from the Flemish government through long-term structural funding Methusalem (CASAS2, Meth/15/04), from the KU Leuven Research Fund (iBOF-21-085 PERSIST), and from the MPI as a fellow. D.V. acknowledges the Research Foundation - Flanders for his Ph.D. fellowship (FWO Grant No 1S45221N). S.F. acknowledges fellowship support from the Chinese Scholarship Council (CSC). L.D.V. acknowledges support from the EU Horizon 2020 Framework Programme (Grant No. 811284).
Open access funded by Max Planck Society.
© 2022 The Authors. Published by American Chemical Society.
All Science Journal Classification (ASJC) codes
- Chemistry (miscellaneous)
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Energy Engineering and Power Technology
- Materials Chemistry