Collective Spectral Diffusion of Defect Luminescence in CH₃NH₃PbI₃ Halide Perovskites

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Solution-processed halide perovskites (HPs) exhibit remarkable optoelectronic properties.
• Their unique characteristics stem from interactions between the polar lattice, charge carriers, and defects.

Purpose of the Study:

• Investigate spectral diffusion (SD) in defect states of MAPbI3 using microphotoluminescence (μPL) spectroscopy.
• Characterize the nature of spectral fluctuations and their relationship to lattice dynamics and defect interactions.

Main Methods:

• Utilized microphotoluminescence (μPL) spectroscopy to analyze ultrasharp emission lines (<500 μeV at 4 K) in MAPbI3.
• Analyzed temporal spectral fluctuations, photon statistics, and excitation power dependence.

Main Results:

• Observed spectral diffusion attributed to collective behavior of an ensemble of emitters, confirmed by the absence of photon antibunching.
• Documented spectral fluctuations ranging from hundreds of μeV to meV, including continuous jitter and discrete jumps.
• Found that spectral jump frequency increases with excitation power, with a transition from Gaussian to Lorentzian statistics.
• Identified correlated spectral fluctuations among distinct defect states, indicating coupling to shared nanoenvironmental perturbations.

Conclusions:

• Spectral diffusion in HPs is a collective phenomenon influenced by the dynamic lattice.
• Correlated fluctuations suggest coupled defect states interacting with slow, correlated lattice deformations.
• These findings offer new insights into defect-lattice interactions in halide perovskites.