State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai, 200433, China.
Department of Macromolecular Science, Fudan University, Shanghai, 200433, China.
Nat Commun. 2019 Feb 14;10(1):756. doi: 10.1038/s41467-019-08573-8.
Owing to strong light-matter interaction, two-dimensional (2D) organic crystal is regarded as promising materials for ultrasensitive photodetectors, however it still received limited success due to degraded photoelectrical response and problems in controllable growth. Here, we find the growth of 2D organic crystal obeys Gibbs-Curie-Wulff law, and develop a seed-epitaxial drop-casting method to grow millimeter-sized 1,4-bis(4-methylstyryl)benzene 2D crystals on SiO/Si in a thermodynamically controlled process. On SiO/Si, a distinct 2D limit effect is observed, which remarkably enhances internal photoresponsivity compared with bulk crystals. Experiment and calculation show the molecules stack more compactly at the 2D limit, thus better molecular orbital overlap and corresponding changes in the band structure lead to efficient separation and transfer of photo-generated carriers as well as enhanced photo-gating modulation. This work provides a general insight into the growth and the dimension effect of the 2D organic crystal, which is valuable for the application in high-performance photoelectrical devices.
由于强的光-物质相互作用，二维（2D）有机晶体被认为是超灵敏光探测器的有前途的材料，然而，由于光电响应的退化和可控生长的问题，它仍然受到限制。在这里，我们发现 2D 有机晶体的生长遵循吉布斯-居里-沃尔夫定律，并开发了一种种子外延滴铸法，在热力学控制过程中在 SiO2/Si 上生长毫米级的 1,4-双（4-甲基苯乙烯基）苯 2D 晶体。在 SiO2/Si 上，观察到明显的 2D 极限效应，与体晶体相比，内部光响应性显著增强。实验和计算表明，分子在 2D 极限处堆积更紧密，从而更好的分子轨道重叠和相应的能带结构变化导致光生载流子的有效分离和转移以及增强的光门调制。这项工作提供了对 2D 有机晶体的生长和维度效应的一般了解，这对于高性能光电设备的应用是有价值的。
