Research onterahertz spectral characteristics of organic-inorganic hybrid perovskite thin films

Objective The terahertz spectral characteristics of two-dimensional (PEA)₂PbI₄ perovskite thin films are strongly dependent on their crystallographic orientation and defect density, which are primarily determined by spin-coating parameters. This study systematically investigates the correlation between spin-coating speed (500-2500 r/min) and terahertz optical properties to optimize device performance.

Methods High-quality (PEA)₂PbI₄ thin films were prepared by optimizing the spin-coating process (1500 r/min, 30 s) with a precursor solution of PEAl∶ PbI₂=2∶1 in DMF solvent. The films were characterized using terahertz time-domain spectroscopy (THz-TDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Key parameters including absorption coefficient, dielectric loss, and refractive index were measured across 0.1-2.2 THz range.

Results and Discussions The 1500 r/min samples exhibited optimal performance with: Characteristic absorption peak at 1.5 THz (38 cm⁻¹); Low dielectric loss (1.72 at 0.3 THz); High refractive index (2.85 at 1.0 THz); Preferred (00h) crystal orientation confirmed by XRD. XRD and SEM analyses revealed that the 1500 r/min condition achieved the best balance between film uniformity and crystallinity, minimizing defect-induced phonon scattering. The 1.5/1.8 THz dual-peak absorption structure originates from Pb-I framework vibrations and interlayer coupling effects.

Conclusions This work demonstrates that spin-coating speed critically influences the terahertz response of 2D perovskite films through microstructure modulation. The optimized 1500 r/min films show exceptional performance for terahertz modulators and filters, achieving 30% modulation depth. These findings provide fundamental insights into structure-property relationships and practical guidelines for developing high-performance terahertz functional devices.