Abstract
The composite assembly of C60 and CdS Quantum Dots (QDs) on ITO substrate was prepared by Langmuir-Blodgett (LB) technique using arachic acid (AA), stearic acid (SA) and octadecanyl amine (OA) as additives. Photoassisted conductive atomic force microscopy was used to make point contact current-voltage (I-V) measurements on both the CdS QDs and the composite assembly of C60/CdS. The result make it clear that the CdS, C60/CdS assemblies deposited on ITO substrate showed linear characteristics and the current increased largely under illumination comparing with that in the dark. The coherent, nonresonant tunneling mechanism was used to explain the current occurrence. It is considered that the photoinduced carriers CdS QDs tunneled through alkyl chains increased the current rapidly.
Highlights
INTRODUCTIONDue to its special highly symmetric cage-like structure and its subsequent discovery of the excellent electron acceptor capability, C60 family has been widely used for novel optoelectronic materials with the characteristic of photoinduced charge transfer.[1,2,3,4,5,6] Hwang found the photoinduced electron transport across a lipid bilayer mediated by C70 by electrochemical method, which is the first time to achieve the charge transfer across membrane by use of C70.1 This electron transport across a membrane is central to photosynthesis, which has important applications in light energy storage and conversion, photoelectronic device, biosensor and so on.[7,8,9,10] On the other hand, due to the special optical effect from the quantum size, quantum dots (QDs) have been widely used in many areas, such as solar energy cells, biosensor application.[11,12] Among many Quantum Dots (QDs), CdS was the most in-depth research, and the most widely used in the application
The composite assembly of C60 and CdS Quantum Dots (QDs) on ITO substrate was prepared by Langmuir-Blodgett (LB) technique using arachic acid (AA), stearic acid (SA) and octadecanyl amine (OA) as additives
We directly investigate the photoelectronic property of the junction of CdS QDs and C60/CdS by PC-AFM
Summary
Due to its special highly symmetric cage-like structure and its subsequent discovery of the excellent electron acceptor capability, C60 family has been widely used for novel optoelectronic materials with the characteristic of photoinduced charge transfer.[1,2,3,4,5,6] Hwang found the photoinduced electron transport across a lipid bilayer mediated by C70 by electrochemical method, which is the first time to achieve the charge transfer across membrane by use of C70.1 This electron transport across a membrane is central to photosynthesis, which has important applications in light energy storage and conversion, photoelectronic device, biosensor and so on.[7,8,9,10] On the other hand, due to the special optical effect from the quantum size, quantum dots (QDs) have been widely used in many areas, such as solar energy cells, biosensor application.[11,12] Among many QDs, CdS was the most in-depth research, and the most widely used in the application. To study the possible photoinduced electron transfer process between C60 and CdS, the electrode-organic molecules-electrode junctions need to be built firstly. This kind of junction can be fabricated by Langmuir-Blodgett (LB), which can get the expected thickness and molecular arrangement of ultrathin films at the molecular level, realization the position of the functional molecules.[13,14]. The I−V curves clearly demonstrate that the linear behavior was observed under illumination, which resulted from the photoinduced carriers tunneling through monomolecular layer between C60 and CdS QDs. It was proposed that these junctions provide may be useful experimental tools for investigations of electron tunnel across organic thin films and can be developed into practically useful microelectronic components in the future
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