Optoelectronic response of hybrid PbS-QD/graphene photodetectors
Optoelectronic response of hybrid PbS-QD/graphene photodetectors
复制标题
DOI：
10.1063/1.5132562
复制
发表时间：
2019-12-21
影响因子：
4.4
通讯作者：
Vazquez-Mena, Oscar
中科院分区：
文献类型：
--
作者：
Ahn, Seungbae;Chung, Hyeseung;Vazquez-Mena, Oscar
硫化铅量子点由于具有高的吸收系数和可调的带隙，被广泛应用于各种光电子器件中。然而，量子点薄膜的低迁移率导致电荷收集和器件性能较差。通过将量子点和石墨烯结合成石墨烯/量子点复合光电探测器，量子点的光载流子转移到石墨烯上，改善了电荷的收集和传输，大大提高了光响应性。在这里，我们对量子点尺寸和量子点膜厚度等关键调谐参数如何影响响应度、光谱响应和时间响应进行了系统的分析。报道了不同尺寸的PbS量子点的吸收系数、折射率(n，k)、穿透深度和能带宽度。我们系统地研究了Gr/QD混合体的光电流、光响应率、时间响应和功率密度依赖关系随量子点尺寸的变化情况。硫化铅量子点的带隙在0.86 eV到1.39 eV之间可调。时间响应表明，在功率密度为10(-5)mW/cm(2)的情况下，对于不同的量子点大小，可以实现亚秒级调制，响应率可达10(7)A/W。我们还研究了厚度对探测器性能的影响，讨论了光吸收和电荷收集之间的折衷对厚度的限制。我们描述了随着量子点薄膜的增厚，光学响应如何向红外方向移动。对于厚度为15 0 nm到1µm的石墨烯/量子点器件，获得了小于1 S的时间响应，这一系统的研究为设计石墨烯/量子点复合探测器及其光谱响应和性能提供了重要的指导。由AIP出版公司授权出版。
Lead sulfide quantum dots (QDs) have been widely used for various optoelectronic devices due to their high absorption coefficient and tunable bandgap. However, the low mobility of QD films results in poor charge collection and device performance. By combining QDs with graphene into hybrid graphene/QD photodetectors, photocarriers from QDs are transferred to graphene, improving charge collection and transport, drastically increasing the photoresponsivity. Herein, we carry a systematic analysis on how critical tuning parameters such as QD size and QD film thickness affect responsivity, spectral response, and time response. We report the absorption coefficient, refractive index (n, k), penetration depth, and energy bandgap of PbS QDs of different sizes. We study systematically how the photocurrent, photoresponsivity, time response, and power density dependence vary with QD size in hybrid Gr/QD. The bandgap of lead sulfide quantum dots was size-tuned between 0.86 and 1.39 eV. The time response shows that subsecond modulation can be achieved for different QD sizes with a responsivity up to 10(7) A/W at power densities of 10(-5) mW/cm(2). We also studied how the performance of the photodetectors is affected by the thickness, discussing the limitations on the thickness by the compromise between light absorption and charge collection. We describe how the optical response shifts toward the infrared as QD films get thicker. Time responses below 1 s are obtained for graphene/QD devices with thickness from 150 nm to 1 mu m. This systematic study provides important guidelines to design hybrid graphene/QD photodetectors and tune their spectral response and performance. Published under license by AIP Publishing.