1：Experimental Design and Method Selection:

High-quality epitaxial single crystalline (C4H9NH3)2PbI4 flakes with controlled dimensions were grown using cold-wall chemical vapor epitaxy. Temperature-dependent micro photoluminescence (PL) was used to study electron-phonon coupling and structural phase transitions.

2：Sample Selection and Data Sources:

Single crystalline flakes were grown on muscovite mica and Si substrates. Optical microscopy, X-ray diffraction (XRD), and temperature-dependent PL spectra were used for characterization.

3：List of Experimental Equipment and Materials:

Customized cold-wall chemical vapor deposition system, Nikon Ti-S inverted optical microscope, Panalytical X’pert PRO MPD XRD, Picoquant 405 nm laser, Renishaw 2000 Raman Spectrometer, Zeiss Supra EDX.

4：Experimental Procedures and Operational Workflow:

Co-evaporation of PbI2 and C4H9NH2·HI was applied to provide vapor phase precursors for epitaxial growth. Optical microscopy and XRD were used to reveal crystal structure and epitaxial relations. Temperature-dependent PL spectra were collected to study phase transitions and electron-phonon coupling.

5：Data Analysis Methods:

Electron-phonon coupling was characterized by a phenomenological formula considering inhomogeneous broadening, acoustic phonon scattering, Fr?hlich interaction, and scattering from impurities.