SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Korea.
School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746, Korea.
Nanoscale. 2016 Apr 28;8(17):9193-200. doi: 10.1039/c6nr00654j.
We investigated, for the first time, the photoresponse characteristics of solution-synthesized MoS2 phototransistors. The photoresponse of the solution-synthesized MoS2 phototransistor was solely determined by the interactions of the photogenerated charge carriers with the surface adsorbates and the interface trap sites. Instead of contributing to the photocurrent, the illumination-generated electron-hole pairs were captured in the trap sites (surface and interface sites) due to the low carrier mobility of the solution-synthesized MoS2. The photogenerated holes discharged ions (oxygen and/or water) adsorbed onto the MoS2 surface and were released as neutral molecules. At the same time, the photogenerated electrons filled the traps present at the interface with the underlying substrate during their transport to the drain electrode. The filled trap sites significantly relieved the band bending near the surface region, which resulted in both a negative shift in the turn-on voltage and an increase in the photocurrent. The time-dependent dynamics of the solution-synthesized MoS2 phototransistors revealed persistent photoconductance due to the trapped electrons at the interface. The photoconductance was recovered by applying a short positive gate pulse. The instantaneous discharge of the trapped electrons dramatically reduced the relaxation time to less than 20 ms. This study provides an important clue to understanding the photoresponses of various optoelectronic devices prepared using solution-synthesized two-dimensional nanomaterials.
我们首次研究了溶液合成的 MoS2 光电晶体管的光电响应特性。溶液合成的 MoS2 光电晶体管的光电响应仅由光生电荷载流子与表面吸附物和界面陷阱位置的相互作用决定。由于溶液合成的 MoS2 载流子迁移率较低，光生电子-空穴对不是在陷阱位置（表面和界面位置）中被捕获，而是在陷阱位置中被捕获，而不是贡献光电流。光生空穴会释放吸附在 MoS2 表面上的离子（氧和/或水），并作为中性分子释放。同时，光生电子在向漏极传输过程中填充了与基底界面处存在的陷阱。填充的陷阱位置显著减轻了表面区域附近的能带弯曲，这导致开启电压的负向移动和光电流的增加。溶液合成的 MoS2 光电晶体管的时间相关动力学揭示了由于界面处的捕获电子而产生的持续光导现象。通过施加短的正栅极脉冲可以恢复光导。捕获电子的瞬时放电大大降低了弛豫时间，使其小于 20ms。这项研究为理解使用溶液合成二维纳米材料制备的各种光电设备的光电响应提供了重要线索。
