Amsterdam Samuel H, Marks Tobin J, Hersam Mark C
Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
Department of Materials Science and Engineering and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
J Phys Chem Lett. 2021 May 20;12(19):4543-4557. doi: 10.1021/acs.jpclett.1c00799. Epub 2021 May 10.
The surface sensitivity and lack of dielectric screening in two-dimensional (2D) materials provide numerous intriguing opportunities to tailor their properties using adsorbed π-electron organic molecules. These organic-2D mixed-dimensional heterojunctions are often considered solely in terms of their energy level alignment, i.e., the relative energies of the frontier molecular orbitals versus the 2D material conduction and valence band edges. While this simple model is frequently adequate to describe doping and photoinduced charge transfer, the tools of molecular chemistry enable additional manipulation of properties in organic-2D heterojunctions that are not accessible in other solid-state systems. Fully exploiting these possibilities requires consideration of the details of the organic adlayer beyond its energy level alignment, including hybridization and electrostatics, molecular orientation and thin-film morphology, nonfrontier orbitals and defects, excitonic states, spin, and chirality. This Perspective explores how these relatively overlooked molecular properties offer unique opportunities for tuning optical and electronic characteristics, thereby guiding the rational design of organic-2D mixed-dimensional heterojunctions with emergent properties.
二维（2D）材料的表面敏感性和缺乏介电屏蔽效应，为利用吸附的π电子有机分子来调整其性质提供了众多有趣的机会。这些有机-二维混合维度异质结通常仅从其能级排列的角度来考虑，即前沿分子轨道与二维材料导带和价带边缘的相对能量。虽然这个简单的模型通常足以描述掺杂和光致电荷转移，但分子化学工具能够对有机-二维异质结的性质进行额外的调控，而这在其他固态系统中是无法实现的。要充分利用这些可能性，需要考虑有机吸附层除能级排列之外的细节，包括杂化和静电作用、分子取向和薄膜形态、非前沿轨道和缺陷、激子态、自旋和手性。本视角探讨了这些相对被忽视的分子性质如何为调节光学和电子特性提供独特的机会，从而指导具有新兴性质的有机-二维混合维度异质结的合理设计。
