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He J.,East China Normal University | Sun L.,East China Normal University | Zhang K.,East China Normal University | Wang W.,East China Normal University | And 5 more authors.
Applied Surface Science | Year: 2013

Quaternary Cu2ZnSnS4 (CZTS) thin films were deposited on heated glass substrates directly from a non-stoichiometric quaternary CZTS target by radio-frequency (RF) magnetron sputtering process, followed by post-sulfurization in atmosphere of Ar + H2S(5%). The results of X-ray diffraction (XRD), Raman spectra, and scanning electron microscope (SEM) show that post-annealed process can improve the crystallinity of CZTS thin films. Both XRD and Raman spectra analysis indicate the internal compressive stress relaxes in post-annealed CZTS thin films. Further transmission spectra demonstrate that the band gaps of post-annealed CZTS thin films are smaller than those of as-deposited due to the relaxation of internal compressive stress and the increase of Cu content in the post-annealed CZTS films. © 2012 Elsevier B.V. All rights reserved. Source


Wu Y.,Tongji University | Xia Z.,Tongji University | Liang Z.,Tongji University | Zhou J.,Tongji University | And 3 more authors.
Optics Express | Year: 2014

Semiconducting nanowire arrays have emerged as a promising route toward achieving high efficiencies in solar cells. Here we propose a perpendicular elliptical silicon nanowire (PEE-SiNW) array for broadband light absorption in thin film silicon solar cells. Simulation results reveal that light absorption enhancement is originated from the split of the principal modes as well as the excitation of high order modes caused by the asymmetry of the elliptical nanowires and the enhanced mode coupling between adjacent elliptical nanowires attained by the appropriate arrangement of nanowires. An ultimate efficiency of 29.1% is achieved for the optimal PEE-SiNW array, which is 16.4% higher than that of the circular SiNW array with the same fill fraction. © 2014 Optical Society of America. Source


Tao J.,East China Normal University | Liu J.,East China Normal University | He J.,East China Normal University | Zhang K.,East China Normal University | And 5 more authors.
RSC Advances | Year: 2014

Cu2ZnSnS4 (CZTS) absorbers have been successfully deposited on tin-doped indium oxide coated glass (ITO/glass) substrates by sulfurization process of co-electrodeposited Cu-Zn-Sn-S precursor thin films at various annealing temperatures ranging from 500 to 580 °C for 30 min in an atmosphere of Ar-H2S (6.5%). The effects of sulfurization temperature on the structure, morphology, composition and optical properties of CZTS thin films have been investigated in details. XRD and Raman measurements reveal that the intensity of preferential orientation along the (112) direction becomes relatively more intense and sharp with increasing annealing temperature. The morphological and chemical composition studies indicate the formation of compact and homogenous CZTS thin films with Cu-poor and Zn-rich composition at a sulfurization temperature of 560 °C. And its band gap energy is around 1.50 eV. The AZO/i-ZnO/CdS/CZTS/ITO/glass thin-film solar cell is fabricated with the CZTS absorber layer grown at an optimized sulfurization temperature of 560 °C. It shows a power conversion efficiency of 1.98% for a 0.25 cm 2 area with Voc = 490 mV, Jsc = 9.69 mA cm -2 and FF = 40.03%. © The Royal Society of Chemistry 2014. Source


He J.,East China Normal University | Sun L.,East China Normal University | Ding N.,East China Normal University | Kong H.,East China Normal University | And 6 more authors.
Journal of Alloys and Compounds | Year: 2012

Cu 2ZnSn(S,Se) 4 (CZTSSe) thin films have been firstly deposited on heating quartz substrates by pulsed laser deposition (PLD) method using one-step process. The results of energy dispersive X-ray (EDX) spectroscopy show that there are some discrepancies of the elemental composition between targets and thin films. However, structural and optical properties of CZTSSe thin films show good tolerance to the composition deviation from stoichiometry. Both X-ray diffraction (XRD) and Raman spectra analysis indicate the internal compressive stress exists in CZTSSe thin films. Further transmission spectra demonstrate that the band gaps of CZTSSe thin films are higher than those of CZTSSe bulks. The internal compressive stress and the deficiency of Cu content in the films contribute to the enlargement of the band gaps of CZTSSe thin films. © 2012 Elsevier B.V. All rights reserved. Source


He J.,East China Normal University | Sun L.,East China Normal University | Chen Y.,East China Normal University | Jiang J.,Shanghai Center for Photovoltaics | And 3 more authors.
Journal of Power Sources | Year: 2015

Effects of sulfurization pressure on composition, morphology and microstructure of kesterite Cu2ZnSnS4 (CZTS) thin films obtained by sulfurization of the metallic layers have been investigated in detail. It is found that the S content in the CZTS thin films is strongly dependent on the sulfurization pressure. The CZTS thin films sulfurized under low sulfurization pressure have S-poor state with a bilayer structure, while it exhibits sufficient amounts of sulfur under high sulfurization pressure with grain growth throughout the entire absorber film. X-ray diffraction data indicate lower sulfurization pressure during the CZTS grain growth process can induce the formation of more structural defects in the CZTS lattice and the CZTS thin films sulfurized under high sulfurization pressure have more random orientation. Furthermore, ZnS and MoS2 phase exist in all samples determined by Fourier transform infrared reflectance spectroscopy as complementary to Raman spectroscopy. The solar cell fabricated with the CZTS thin film under 10 Torr sulfurization pressure shows the best conversion efficiency of 3.52% (VOC = 484 mV, JSC = 14.56 mA cm-2, FF = 50.1%). © 2014 Elsevier B.V. Source

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