Circularly Polarized Light-Induced Microwave Conductivity Measurement: Rapid Screening Technique of Electronic Conductivity in Chiral Molecular Materials

Abstract

We developed circularly polarized light–time-resolved microwave conductivity (CPL–TRMC) for investigation of the CPL-dependent photoinduced charge carrier dynamics in chiral materials with chiroptical properties. Chiral R- or S-perylenediimide (PDI) molecular thin films were paired with handedness-sorted (6,5) and (11,–5) single-walled carbon nanotube (SWCNT) films to compose a donor (D)–acceptor (A) system for the spin-dependent charge separation process, and the D–A system was examined through linear and circular polarization-dependent steady-state and time-resolved measurements. The R-PDI-(6,5) film exhibited strong enhancement in circular dichroism (CD) and revealed a reversed transient conductivity signal, relative to the polarity of CD in CPL–TRMC measurement upon excitation of the E₁₁ state, which is interpreted as arising from a spin-dependent initial charge separation process. Through linear polarization-dependent flash photolysis TRMC and circular polarization-resolved femtosecond transient absorption, we could deduce that sub-picosecond intertubular charge separation upon E₁₁ excitation in SWCNT was responsible for the spin-dependent photoconductivity transients observed in CPL–TRMC measurements.