Dynamic tuning of ENZ wavelength in conductive polymer films via polaron excitation

TL;DR

This paper demonstrates reversible, ultrafast tuning of the epsilon-near-zero wavelength in organic PEDOT:PSS films by manipulating polaron states with optical excitation, enabling dynamic control for advanced photonic applications.

Contribution

It introduces a method for dynamically tuning ENZ wavelengths in p-type organic semiconductors via polaron excitation, a novel approach for flexible optoelectronic devices.

Findings

Achieved up to 150 nm ENZ wavelength shift.

Observed ultrafast polaron dynamics with subpicosecond time constants.

Demonstrated reversible ENZ tuning through optical excitation.

Abstract

Traditional metal and n-type doped semiconductor materials serve as emerging epsilon-near-zero (ENZ) materials, showcasing great potential for nonlinear photonic applications. However, a significant limitation for such materials is the lack of versatile ENZ wavelength tuning, and thus dynamic tuning of the ENZ wavelength remains a technical challenge, thereby restricting their potential applications, such as multi-band communications. Here, dynamic tuning of the ENZ wavelength in p-type organic PEDOT: PSS films is achieved through a reversible change in hole concentrations originated from the polaron formation/decoupling following optical excitation, and a tunable ENZ wavelength shift up to 150 nm is observed. Experimental investigations about ultrafast dynamics of polaron excitation reveal an approximately 80 fs time constant for polaron buildup and an approximately 280 fs time constant for polaron decoupling, indicating the potential of reversal ultrafast switching for the ENZ wavelength within subpicosecond time scale. These findings suggest that $p$--type organic semiconductors can serve as a novel platform for dynamically tuning the ENZ wavelength through polaron excitation, opening new possibilities for ENZ--based nonlinear optical applications in flexible optoelectronics.