Resolving Excited-State Dynamics of Two-Dimensional Layered (PEA)₂SnI₄ Polycrystalline Thin Films in Fabry-Pérot...

Area of Science:

• Materials Science
• Quantum Optics
• Spectroscopy

Background:

• Exciton-photon hybrid states in 2D hybrid organic-inorganic perovskites (2D-HOIPs) are key for low-threshold lasing.
• Understanding excited-state dynamics, especially dark states (DS), in polycrystalline films is crucial but underexplored.

Purpose of the Study:

• To investigate the transient signatures and decay pathways of hybrid states in (PEA)2SnI4 polycrystalline films within Fabry-Pérot cavities.
• To clarify the role of dark states (DS) in the transient absorption response of these hybrid systems.

Main Methods:

• Utilized sub-20 femtosecond (fs) transient absorption (TA) spectroscopy.
• Employed Fabry-Pérot cavities with (PEA)2SnI4 polycrystalline films.
• Analyzed detuning-dependent decay pathways and transient signatures.

Main Results:

• Identified a short-lived upper polariton (UP) population whose decay rate correlates with photon fraction.
• Observed a long-lived negative band in negatively detuned cavities, identified as DS-like states.
• Provided direct evidence for DS-like state contribution to the long-lived TA signal.

Conclusions:

• Dark states (DS) spectroscopically contribute to the transient absorption response in 2D-HOIP cavities.
• Clarified the femtosecond transient absorption (fs-TA) signatures of hybrid states in (PEA)2SnI4 films.
• Offers photophysical insights for designing low-threshold lasers using scalable 2D-HOIP films.