Solution-Processed Hybrid Polymer-Quantum Dot Nanocomposite for Infrared Photodetection and Photorefractivity
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Solution-Processed Hybrid Polymer-Quantum Dot Nanocomposite for Infrared Photodetection and Photorefractivity Kaushik Roy Choudhury1, Won Jin Kim2,3, Yudhisthira Sahoo1, Kwang-Sup Lee2,3, and Paras N. Prasad1 1 Departments of Physics and Chemistry, Institute for Lasers Photonics and Biophotonics, University at Buffalo, The State University of New York, Buffalo, NY, 14260 2 Institute for Lasers Photonics and Biophotonics, University at Buffalo, The State University of New York, Buffalo, NY, 14260 3 Department of Polymer Science and Engineering, Hannam University, Daejeon, 306-791, Korea, Democratic People's Republic of
ABSTRACT Successful integration of solution-processible nanocrystal quantum dots, active over a wide spectral range in the infrared, organic molecules and polymers, to fabricate efficient photoconductive and photorefractive devices operational at important optical communication wavelengths is achieved. Sensitization of the polymeric composites by quantum dots led to high photocurrents at 1340 nm, yielding a high photoconductive quantum efficiency. In the photorefractive composites, pronounced two-beam coupling was observed, leading to good optical gains achievable by low-power continuous-wave illumination. The photoresponse was further extended to 1550 nm. A steady state diffraction efficiency was obtained in the dynamic refractive-index gratings with appreciable response times. In order to enhance the photoconductive performance of the devices, the organic semiconductor pentacene was incorporated into the hybrid composite through a soluble presursor. At the operating wavelength of 1340 nm, the photocurrent increased significantly as the amount of pentacene in the composite was increased, resulting in a spectacular improvement of external quantum efficiency.
INTRODUCTION Semiconductor nanocrystal quantum dots (QDs), by virtue of the fact that many of their physical properties can be tuned via simple chemical means, are attractive as components of optoelectronic devices. Composites of QDs, organic semiconductors and polymers offer great promise for the fabrication of large-area devices on flexible substrates using inexpensive solution processing. Significant research efforts have resulted in visible and infrared light-emitting diodes [1] and photodetectors [2,3], field-effect transistors [4,5], and photovoltaic cells [6,7]. On the other hand, custom-tailored organic photorefractive (PR) materials have shown enormous potential for a wide range of applications, namely, dynamic holography, pattern recognition, reversible data storage, and optical image processing [8,9]. But, devices with spectral response in the technologically important near-infrared (IR) wavelength range need still be realized, mainly due to the lack of IR-active organic photosensitizers. With the advent of colloidal semiconductor QDs with size tunable absorption, a novel route to sensitize the polymeric PRs has opened up,
leading to next-generation hybrid organic-inorganic nanocomposites. In this paper, we demonstrate e
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