Yongju Park

Aligned networks of cadmium sulfide nanowires for highly flexible photodetectors with improved photoconductive responses

We developed a simple but efficient method to mass-produce highly flexible and high-performance photodetectors based on aligned cadmium sulfide (CdS) nanowire (NW) networks. In this method, the CdS NWs were selectively aligned along the molecular patterns on flexible substrates via a direct assembly method, and the aligned CdS NW patterns were utilized as the channels of flexible photodetectors. The photodetectors based on the aligned CdS NWs exhibited ∼10 times higher photosensitivity and ∼100 times faster photoresponse than those based on randomly oriented NW networks. In addition, the flexible photodetectors exhibited stable photoconductive characteristics even when these were bent down to the radius of curvature of 0.2 mm. This research may pave the way for the large-scale fabrication of low-cost and high performance flexible photodetectors based on the aligned NW networks.

Graphene-nanowire hybrid structures for high-performance photoconductive devices†

Graphene–CdS nanowire (NW) hybrid structures with high-speed photoconductivity were developed. The hybrid structure was comprised of CdS NWs which were selectively grown in specific regions on a single-layer graphene sheet. The photoconductive channels based on graphene–CdS NW hybrid structures exhibited much larger photocurrents than graphene-based channels and much faster recovery speed than CdS NW network-based ones. Our graphene–CdS NW structures can be useful because they were much faster than commercial CdS film-based photodetectors and had photocurrents large enough for practical applications.

Study of the Cesium Carbonate (Cs2CO3) Inter Layer Fabricated by Solution Process on P3HT:PCBM Solar Cells

In this paper, we studied the effect of the electron injection layer, Cesium carbonate (Cs2CO3), thickness on the performance of organic solar cell (OSC) based on blends of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester fullerene derivative (PCBM). The polymer solar cell consists of molybdenum-oxide (MoO3) as a hole injection layer, P3HT and PCBM bulk hetero junction as an active layer, and Cesium carbonate (Cs2CO3) as an electron injection layer. We measured each device by current-voltage measurement and impedance spectroscopy which is widely used for equivalent circuit analysis of solid state structures. The device with the Cs2CO3 layer showed about 8–10% higher JSC and about 6–8% higher power conversion efficiency compared with the devices without the Cs2CO3 layer.

High‐Performance Photoconductive Channels Based on (Carbon Nanotube)–(CdS Nanowire) Hybrid Nanostructures

A photoconductive channel based on hybrid nanostructures comprising carbon nanotubes (CNTs) and CdS nanowires is fabricated by a directed assembly strategy and catalyst-assisted chemical vapor deposition (CVD). The photoconductive channels simultaneously exhibit large photocurrent and fast response speed. Furthermore, it can be easily applied to surfaces that are not flat, such as a glass tube. This is a simple but efficient strategy for various optoelectronic applications.

Bi-Assisted CdTe/CdS Hierarchical Nanostructure Growth for Photoconductive Applications

We developed a method to control the structure of CdTe nanowires by adopting Bi-mixed CdTe powder source to a catalyst-assisted chemical vapor deposition, which allowed us to fabricate CdTe/CdS hierarchical nanostructures. We demonstrated that diverse nanostructures can be grown depending on the combination of the Bi powder and film catalysts. As a proof of concepts, we grew CdTe/CdS branched nanowires for the fabrication of photodetectors. The hierarchical nanostructure-based photodetectors showed an improved photoresponsivity compared to the single CdTe nanowire (NW)-based photodetector. Our strategy can be a simple but powerful method for the development of advanced optoelectronic devices and other practical applications.