Abstract：
Layered semiconductors of the V-VI group have attracted considerable attention in optoelectronic applications owing to their atomically thin structures. They offer thickness-dependent optical and electronic properties, promising ultrafast response time, and high sensitivity. Compared to the bulk, 2D bismuth selenide (Bi2Se3) is recently considered a highly promising material. In this study, 2D nanosheets are synthesized by prolonged sonication in two different solvents, such as N-methyl-2-pyrrolidone (NMP) and chitosan-acetic acid solution (CS-HAc), using the liquid-phase exfoliation (LPE) method. X-ray diffraction confirms the amorphous nature of exfoliated 2D nanosheets with maximum peak intensity at the same position (015) crystal plane as that obtained in its bulk counterpart. SEM confirms the thin 2D nanosheet-like morphology. Successful exfoliation of Bi2Se3 nanosheets up to five layers is achieved using CS-HAc solvent. The as-synthesized 2D nanosheets in different solvents are employed to fabricate the photodetector. At minimum selected power density, the photodetector fabricated using exfoliated ultrathin 2D nanosheets exhibits the highest range of responsivity, varying from 15 to 2.5 mA/W, and detectivity ranging from 2.83 × 109 to 6.37 × 107. Ultrathin 2D Bi2Se3 nanosheets have fast rise and fall times, ranging from 0.01 to 0.12 and 0.01 to 0.06 s, respectively, at different wavelengths. Ultrathin Bi2Se3 nanosheets have improved photodetection parameters as compared to multilayered nanosheets due to the high surface to volume ratio, reduced recombination and trapping of charge carrier, improved carrier confinement, and faster carrier transport due to the thin layer.
摘要：
V-VI族的层状半导体由于其原子级薄的结构而在光电应用中引起了极大的关注。它们提供依赖于厚度的光学和电子特性，有希望的超快响应时间，和高灵敏度。与散装相比，2D硒化铋(Bi2Se3)最近被认为是一种非常有前途的材料。在这项研究中,2D纳米片是通过在两种不同的溶剂中长时间超声处理合成的，如N-甲基-2-吡咯烷酮（NMP）和壳聚糖-乙酸溶液（CS-HAc），使用液相剥离(LPE)方法。X射线衍射证实了剥离的2D纳米片的无定形性质,其在与其本体对应物中获得的相同位置(015)晶面处具有最大峰强度。SEM证实了薄的2D纳米片状形态。使用CS-HAc溶剂实现Bi2Se3纳米片最多五层的成功剥离。使用在不同溶剂中合成的2D纳米片制造光电探测器。在选定的最小功率密度下，使用剥离超薄2D纳米片制造的光电探测器表现出最高的响应度范围，从15到2.5mA/W不等，探测范围为2.83×109至6.37×107。超薄2DBi2Se3纳米片具有快速上升和下降时间，范围从0.01到0.12和0.01到0.06s，分别,在不同的波长。与多层纳米片相比，超薄Bi2Se3纳米片具有改进的光电检测参数，这归因于高的表面与体积比，减少电荷载流子的复合和捕获，改进的载流子限制，和更快的载流子传输由于薄层。
