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.

以圆偏振光（circularly polarized light, CPL）作为光子信号核心元件的手性有机光电子学领域，近年来已崛起为下一代光子技术。然而，同时实现高偏振选择性与优异光电子性能仍是该领域面临的核心挑战。超分子二维（2D）手性有机单晶因其无缺陷的结构特性、丰富的分子多样性与可调控形貌，成为解决上述问题的潜在优选方案。本研究通过调控不同混合溶剂体系，自组装制备了具有平行四边形、三角形/六边形形貌的手性苝二酰亚胺准二维单晶。得益于独特的分子堆积模式与超分子手性，这类材料展现出增强的圆二色性（circular dichroism, CD）光谱信号。通过肼进行分子表面n型掺杂后，该手性单晶的电子迁移率突破1.0 cm²·V⁻¹·s⁻¹，这一数值在现有手性有机半导体中处于顶尖水平，同时材料亦具备优异的光电子功能。理论计算表明，n型掺杂所生成的自由基阴离子可提升电子亲和能、或降低能带隙，从而优化电子传输过程。更为关键的是，经掺杂的有机手性单晶可选择性识别CPL的手性旋向，其光响应各向异性因子高达约0.12。上述研究结果表明，经表面掺杂的准二维手性有机单晶在手性光电子领域具备极高的应用潜力。