Few-Layer Organic Crystalline van der Waals Heterojunctions for Ultrafast UV Phototransistors
Few-Layer Organic Crystalline van der Waals Heterojunctions for Ultrafast UV Phototransistors
复制标题
用于超快紫外光电晶体管的几层有机晶体范德华异质结
DOI：
10.1002/aelm.202000062
复制
发表时间：
2020-05-11
影响因子：
6.2
通讯作者：
Li, Yun
中科院分区：
文献类型：
--
作者：
Guo, Jianhang;Jiang, Sai;Li, Yun
由于栅极的存在，使用晶体管结构的有机紫外光探测器可以产生比基于二极管的器件更高的光响应性。然而，这些光电晶体管器件的一个长期问题是响应速度慢，这阻碍了它们的实际应用。在这里，有机紫外光晶体管是使用几层有机晶体范德华(VDW)异质结作为光活性层来构建的。光活化层的厚度甚至小于激子扩散长度，从而消除了激子扩散的瓶颈，并导致限制了跨越异质结界面的相邻分子层内的电荷分离和复合。因此，光电晶体管器件可以表现出显著增强的响应速度(上升和衰减时间分别短至仅接近4ms和6ms)。我们还观察到了与层相关的光响应特性，这加强了几层有机异质结构在光电晶体管器件中的重要性。这项工作不仅为快速响应光电子器件提供了一条有希望的途径，而且也为深入理解分子层精度的光生载流子的微观本质提供了一种新的途径。
Organic UV photodetectors using a transistor architecture can yield higher photoresponsivity than diode-based devices because of the presence of a gate electrode. However, a long-term issue of these phototransistor devices is the slow response speed, which hinders their practical applications. Here, organic UV phototransistors are constructed using few-layer organic crystalline van der Waals (vdW) heterojunctions as the photoactive layers. The thickness of the photoactive layers is even less than the exciton diffusion length, thus removing the exciton-diffusion bottleneck and giving rise to the confinement of charge separation and recombination within the adjacent molecular layers across the heterojunction interface. Hence, the phototransistor devices can exhibit a remarkably enhanced response speed (rise and decay times as short as only approximate to 4 and 6 ms, respectively). The layer-dependent photoresponse characteristics are also observed, reinforcing the great importance of few-layer organic heterostructures in phototransistor devices. This work not only provides a promising avenue toward fast response optoelectronic devices but also presents an in-depth understanding on the microscopic nature of photogenerated charge carriers at the precision of molecular layers.