Near-Infrared Circularly Polarized Light Detection through Chiral Polymer Blends with Enhanced Spin Selectivity

Area of Science:

• Materials Science
• Organic Electronics
• Photonics

Background:

• Detecting circularly polarized light (CPL) in the near-infrared (NIR) band is crucial for applications like spectroscopy and imaging.
• Existing methods for NIR CPL detection are often complex and lack practicality.
• Organic photodetectors offer potential but face challenges in achieving efficient CPL detection, especially in the NIR region.

Purpose of the Study:

• To present a simple and practicable method for NIR CPL detection using blended polymer films.
• To investigate the mechanism of chirality transfer in polymer blends.
• To develop an organic photodetector capable of differentiated CPL detection across a wide wavelength range.

Main Methods:

• Blending chiral polythiophene (P3HT-PPI(D)/P3HT-PPI(L)) with nonchiral random copolymers (CPX).
• Modulating copolymerization and blending ratios to induce chirality transfer via intermolecular forces.
• Characterizing chiral absorption using circular dichroism (CD) spectroscopy and analyzing aggregation and chiral induced spin selectivity (CISS) effect using magnetic conductive atomic force microscopy (mc-AFM).

Main Results:

• Blended films exhibited chiral absorption in the 200-800 nm range, extending into the NIR region.
• Increased polymer aggregation led to a higher CISS effect, confirmed by mc-AFM.
• The developed CPL detector demonstrated differentiated CPL detection over a wide wavelength range and enabled image information encryption via a device array.

Conclusions:

• The developed polymer blending strategy provides a simple and effective route for NIR CPL detection.
• The study elucidates the polymer chiral transfer mechanism and highlights the importance of aggregation and CISS.
• This work paves the way for large-scale integrated implementation of advanced CPL detectors.