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Title: Enhancement of photovoltaic effects and photoconductivity observed in Co-doped amorphous carbon/silicon heterostructures

Abstract

Co-doped amorphous carbon (Co-C)/silicon heterostructures were fabricated by growing Co-C films on n-type Si substrates using pulsed laser deposition. A photovoltaic effect (PVE) has been observed at room temperature. Open-circuit voltage V{sub oc} = 320 mV and short-circuit current density J{sub sc }= 5.62 mA/cm{sup 2} were measured under illumination of 532-nm light with the power of 100 mW/cm{sup 2}. In contrast, undoped amorphous carbon/Si heterostructures revealed no significant PVE. Based on the PVE and photoconductivity (PC) investigated at different temperatures, it was found that the energy conversion efficiency increased with increasing the temperature and reached the maximum at room temperature, while the photoconductivity showed a reverse temperature dependence. The observed competition between PVE and PC was correlated with the way to distribute absorbed photons. The possible mechanism, explaining the enhanced PVE and PC in the Co-C/Si heterostructures, might be attributed to light absorption enhanced by localized surface plasmons in Co nanoparticles embedded in the carbon matrix.

Authors:
;  [1]
  1. Research Center for Solid State Physics and Materials, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009, Jiangsu (China)
Publication Date:
OSTI Identifier:
22590475
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; CARBON; CURRENT DENSITY; DOPED MATERIALS; ELECTRIC POTENTIAL; ENERGY BEAM DEPOSITION; ENERGY CONVERSION; LASER RADIATION; NANOPARTICLES; PHOTOCONDUCTIVITY; PHOTONS; PHOTOVOLTAIC EFFECT; PLASMONS; PULSED IRRADIATION; SILICON; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K

Citation Formats

Jiang, Y. C., and Gao, J., E-mail: jugao@hku.hk. Enhancement of photovoltaic effects and photoconductivity observed in Co-doped amorphous carbon/silicon heterostructures. United States: N. p., 2016. Web. doi:10.1063/1.4961673.
Jiang, Y. C., & Gao, J., E-mail: jugao@hku.hk. Enhancement of photovoltaic effects and photoconductivity observed in Co-doped amorphous carbon/silicon heterostructures. United States. doi:10.1063/1.4961673.
Jiang, Y. C., and Gao, J., E-mail: jugao@hku.hk. 2016. "Enhancement of photovoltaic effects and photoconductivity observed in Co-doped amorphous carbon/silicon heterostructures". United States. doi:10.1063/1.4961673.
@article{osti_22590475,
title = {Enhancement of photovoltaic effects and photoconductivity observed in Co-doped amorphous carbon/silicon heterostructures},
author = {Jiang, Y. C. and Gao, J., E-mail: jugao@hku.hk},
abstractNote = {Co-doped amorphous carbon (Co-C)/silicon heterostructures were fabricated by growing Co-C films on n-type Si substrates using pulsed laser deposition. A photovoltaic effect (PVE) has been observed at room temperature. Open-circuit voltage V{sub oc} = 320 mV and short-circuit current density J{sub sc }= 5.62 mA/cm{sup 2} were measured under illumination of 532-nm light with the power of 100 mW/cm{sup 2}. In contrast, undoped amorphous carbon/Si heterostructures revealed no significant PVE. Based on the PVE and photoconductivity (PC) investigated at different temperatures, it was found that the energy conversion efficiency increased with increasing the temperature and reached the maximum at room temperature, while the photoconductivity showed a reverse temperature dependence. The observed competition between PVE and PC was correlated with the way to distribute absorbed photons. The possible mechanism, explaining the enhanced PVE and PC in the Co-C/Si heterostructures, might be attributed to light absorption enhanced by localized surface plasmons in Co nanoparticles embedded in the carbon matrix.},
doi = {10.1063/1.4961673},
journal = {Applied Physics Letters},
number = 8,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • The photoconductivity of amorphous silicon films is shown to be enhanced by a factor of 25 at long wavelengths when the material is deposited on a rough, reflecting substrate. In a solar cell, this light trapping effect would produce a 4.5-mA/cm/sup 2/ increase in the short circuit current.
  • The potential improvement in stability of hydrogenated silicon-sulfur alloys (a-SiS{sub x}:H) with respect to ordinary hydrogenated amorphous silicon (a-Si:H) has been attributed to the introduction of an additional metastability known as persistent photoconductivity (PPC). In order to examine the PPC process in more detail we examine a series of alloys with large sulfur concentrations (x{gt}0.01). Although these alloys are not useful in photovoltaic devices, the high sulfur concentrations accentuate the PPC effect and allow one to study this effect with little competition from the ordinary Staebler-Wronski effect that dominates the metastable processes that occur in a -Si:H. {copyright} {ital 1997more » American Institute of Physics.}« less
  • The concept of electronic doping is used to explain unexpectedly large values of the diode quality factor (exceeding two) and supralinearity which is sometimes observed in amorphous silicon p-i-n-type diodes and materials, respectively. This suggests the presence of an extra set of defect states in lightly boron-doped films with a capture rate for electrons which is much larger than that of the inherent defect states. We also report that for high-quality undoped intrinsic layers, the photoconductivity versus intensity behavior exhibits sublinear power dependence which increases with intensity in distinct contrast to the previously reported results. We provide a self-consistent modelmore » which is able to explain the above observations.« less
  • Etching and passivation effects of hydrogen treatment of boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) film used as a p layer of p-i-n type amorphous silicon based solar cells using a mercury-sensitized photochemical vapor deposition method were investigated. For the hydrogen treatment of the p-layer film, longer p-layer deposition time was needed to obtain the same thickness as for no hydrogen treatment because of hydrogen etching effect. However, the cell performance was improved by {approximately}7{percent} due to an increase in the open circuit voltage (V{sub oc}) and fill factor (FF) although the p-layer thickness was nearly identical in both cases. Themore » increase in the V{sub oc} and FF could be explained by an increase in the built-in potential due to a decrease in the film activation energy. Moreover, the electrical property improvement of the film was well explained by the passivation effect of a SiH{sub 2}/SiH ratio decrease and a hydrogen content increase calculated from Fourier transformed infrared absorption measurements. {copyright} {ital 1997 American Institute of Physics.}« less
  • A boron-doped hydrogenated amorphous diamondlike carbon (a-DLC:H) was prepared using a mercury-sensitized photochemical vapor deposition (photo-CVD) method. The source gases were B{sub 2}H{sub 6} and C{sub 2}H{sub 4}. By increasing the boron doping ratio (B{sub 2}H{sub 6}/C{sub 2}H{sub 4}) from 0 to 12000 ppm, the dark conductivity increased from {approximately}10{sup {minus}9} to {approximately}10{sup {minus}7} S/cm. A boron-doped a-DLC:H with an energy band gap of 3.8 eV and a dark conductivity of 1.3{times}10{sup {minus}8} S/cm was obtained at a doping ratio of 3600 ppm. By using this film, amorphous silicon (a-Si) solar cells with a novel p-a-DLC:H/p-a-SiC double p-layer structure weremore » fabricated using the photo-CVD method and the cell photovoltaic characteristics were investigated as a function of a-DLC:H layer thickness. The open circuit voltage increased from 0.766 V for the conventional cell with a 40-{Angstrom}-thick p-a-SiC to 0.865 V for the cell with a p-a-DLC:H (15 {Angstrom})/p-a-SiC (40 {Angstrom}) double p-layer structure. The thin ({lt}15 {Angstrom}) p-a-DLC:H layer proved to be an excellent hole emitter as a wide band gap window layer. {copyright} {ital 1998 American Institute of Physics.}« less