Implementation of Metallic Vertical Interconnect Access in Hybrid Intercalated Graphene/Quantum Dot Photodetector for Improved Charge Collection
Implementation of Metallic Vertical Interconnect Access in Hybrid Intercalated Graphene/Quantum Dot Photodetector for Improved Charge Collection
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DOI：
10.3389/fmats.2019.00159
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发表时间：
2019-07-15
影响因子：
3.2
通讯作者：
Vazquez-Mena, Oscar
中科院分区：
文献类型：
--
作者：
Chen, Wenjun;Ahn, Seungbae;Vazquez-Mena, Oscar
胶体量子点（QD）具有低成本加工、强光吸收和直接带隙尺寸可调等优点，在光电和光伏器件中引起了极大的兴趣。然而，它们有限的载流子迁移率和短的扩散长度限制了有效的电荷收集和传输。QD固体膜中的短扩散长度（100-200 nm）将其厚度限制为约200-300 nm，导致在近红外（λ>800 nm）中的吸收差，浪费了部分太阳光并降低了功率转换效率。最近，一种新的架构的基础上，多个石墨烯单层（Gr）插入内部的量子点薄膜被报道，以提高电荷提取超过量子点扩散长度。插层石墨烯层确保在比扩散长度厚的QD膜中收集有效的电荷。然而，由于器件的差的垂直导电性，当厚度>类似于200 nm时，这种架构仍然不能从QD收集载流子。在此，我们提出了制造，优化和实施的插层器件与垂直互连接触，增加载流子收集，和光电流，旨在开发一种新的架构，用于改进的光检测和photoprophics与量子点。首先，我们分析了Gr和QD的各自作用，研究了光吸收，光电流（I-PH）和电导率的演变，作为连续的QD和Gr层添加。我们找到了插层系统中石墨烯层之间的最佳间距，旨在实现光吸收和有效电荷收集之间的最佳折衷。我们的主要贡献是实现每个石墨烯层的垂直互连访问（VIA），以确保从Gr到金电触点的有效电荷转移，从而实现有效的电流收集。我们发现，对于850 nm波长的照明，光电流的嵌入式设备显示出类似的10倍的改善没有过孔的设备。我们还使用背栅电压来监测Gr中的费米能级位移和从QD到Gr的电荷转移。本文提出的具有VIA接触的插层配置是QD光电应用的电荷收集的显著改善，以及提高QD太阳能电池的功率转换效率的有前途的架构。
Colloidal quantum dots (QDs) are of great interest in optoelectronic and photovoltaic devices with low-cost processing, strong light absorption, and size tunable direct band gap. However, their limited carrier mobility and short diffusion length limit efficient charge collection and transport. The short diffusion length in QD solid films, 100-200 nm, limits their thickness to tr approximate to 200-300 nm, resulting in poor absorption in the near-infrared, lambda>800 nm, wasting part of sunlight and reducing power conversion efficiency. Recently, a novel architecture based on multiple graphene monolayers (Gr) intercalated inside QD films was reported to improve charge extraction beyond QDs diffusion length. The intercalated graphene layers ensure efficient charge collected in QD films thicker than the diffusion length. However, this architecture still fails to collect carriers from the QDs when the thickness is > similar to 200 nm due to the poor vertical conductivity of the devices. Herein, we present the fabrication, optimization, and implementation of intercalated devices with vertical interconnecting contacts, increasing carrier collection, and photocurrent, aiming to develop a novel architecture for improved photodetection and photovoltaics with QDs. First, we analyze the individual roles of Gr and QDs, studying the evolution of light absorption, photocurrent (I-ph), and conductivity as successive QD and Gr layers are added. We find the optimal interspacing between graphene layers in the intercalated system, aiming for the best compromise between light absorption and efficient charge collection. Our main contribution is the implementation of vertical interconnect access (VIAs) to each graphene layer to ensuring efficient charge transfer from Gr to the gold electrical contacts for efficient current collection. We show that for 850 nm wavelength illumination, photocurrent of intercalated devices show a similar to 10 fold improvement over devices without VIAs. We also use a back-gate voltage to monitor Fermi level shift in Gr and charge transfer from QDs to Gr. The intercalated configuration with VIAs contacts herein presented is a significant improvement in charge collection for QD optoelectronic applications as well as a promising architecture to enhance the power conversion efficiency for QD solar cells.