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Frontiers of Optoelectronics

Front. Optoelectron.    2017, Vol. 10 Issue (1) : 31-37     DOI: 10.1007/s12200-016-0595-2
Structural, optical and electrical properties of ZnO: B thin films with different thickness for bifacial a-Si:H/c-Si heterojunction solar cells
Dong XU, Sheng YIN(), Xiangbin ZENG, Song YANG, Xixing WEN
School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
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Textured surface boron-doped zinc oxide (BZO) thin films were fabricated by metal organic chemical vapor deposition as transparent conductive oxide (TCO) for solar cells. The surface microstructure was characterized by X-ray diffraction spectrum and scanning electron microscope. The optical transmittance was shown by optical transmittance microscope and the electrical properties were tested by Hall measurements. The thickness of the BZO film has crucial impact on the surface morphology, optical transmittance, and resistivity. The electrical and optical properties as well as surface microstructure varied inconsistently with the increase of the film thickness. The grain size and the surface roughness increased with the increase of the film thickness. The conductivity increased from 0.96×103 to 6.94×103 S/cm while the optical transmittance decreased from above 85% to nearly 80% with the increase of film thickness from 195 to 1021 nm. The BZO films deposited as both front and back transparent electrodes were applied to the bifacial p-type a-Si:H/i-type a-Si:H/n-type c-Si/i-type a-Si:H/n+-type a-Si:H heterojunction solar cells to obtain the optimized parameter of thickness. The highest efficiency of all the samples was 17.8% obtained with the BZO film thickness of 829 nm. Meanwhile, the fill factor was 0.676, the open-circuit voltage was 0.63 V and the short-circuit density was 41.79 mA/cm2. The properties of the solar cells changing with the thickness were also investigated.

Keywords boron-doped zinc oxide (BZO)      metal organic chemical vapor deposition (MOCVD)      heterojunction solar cell      thickness      textured surface      transparent conductive oxide (TCO)     
Corresponding Authors: Sheng YIN   
Just Accepted Date: 14 September 2016   Online First Date: 17 October 2016    Issue Date: 17 March 2017
 Cite this article:   
Dong XU,Sheng YIN,Xiangbin ZENG, et al. Structural, optical and electrical properties of ZnO: B thin films with different thickness for bifacial a-Si:H/c-Si heterojunction solar cells[J]. Front. Optoelectron., 2017, 10(1): 31-37.
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Dong XU
Sheng YIN
Xiangbin ZENG
Xixing WEN
Fig.1  XRD patterns of BZO films with different thickness
Tab.1  Variation of the Bragg angle 2 θ, FWHM and crystal size with thickness
Fig.2  Surface morphology?of the BZO film with the thickness of (a) 195 nm, (b) 383 nm, (c) 607 nm, (d) 829 nm, (e) 1021 nm
Fig.3  Plot of (a) carrier concentration, (b) Hall mobility, and (c) resistivity of the BZO films versus the film thickness
Fig.4  Optical transmittance of BZO films with different thickness
Fig.5  Tauc plots with different thickness
Fig.6  (a) Schematic diagram of the bifacial heterojunction solar cells; (b) current density–voltage (I–V) curves of the bifacial a-Si:H/c-Si heterojunction solar cells applied with the ZnO:B films of 195–1021 nm as electrodes
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