Surface-Doped Quasi-2D Chiral Organic Single Crystals for Chiroptical Sensing

Chiral
organic optoelectronics using circularly polarized light
(CPL) as the key element in the photonic signal has recently emerged
as a next-generation photonic technology. However, it remains challenging
to simultaneously achieve high polarization selectivity and superior
optoelectronic performance. Supramolecular two-dimensional (2D) chiral
organic single crystals may be good candidates for this purpose due
to their defect-free nature, molecular diversity, and morphologies.
Here, quasi-2D single crystals of chiral perylene diimides with parallelogram
and triangle/hexagon morphologies have been selectively fabricated via self-assembly using different cosolvent systems. These
materials exhibit amplified circular dichroism (CD) spectral signals,
due to their molecular packing modes and supramolecular chirality.
Through molecular surface n-doping using hydrazine, chiral single
crystals exhibit electron mobility surpassing 1.0 cm2 V–1 s–1, which is one of the highest
among chiral organic semiconductors, and excellent optoelectronic
functions. Theoretical calculations reveal that the radical anions
formed by n-doping increase the electron affinity and/or reduce the
energy gap, thus facilitating electron transport. More importantly,
the doped organic chiral crystals selectively discriminate CPL handedness
with a high anisotropy factor of photoresponsivity (∼0.12).
These results demonstrate that surface-doped quasi-2D chiral organic
single crystals are highly promising for chiral optoelectronics.