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ABSTRACT: This paper presents the thermal effect on the performance of a GaAs thin-film solar cell with a 50-200- μm-thick copper (Cu) substrate. The GaAs thin-film solar cell is fabricated by transferring a GaAs solar cell on a Cu substrate with a AuGe/Au mirror. The thin-film solar cells with sufficiently thick Cu substrates exhibit significant performance stability (e.g., V <sub>oc</sub>, J <sub>sc</sub>, and FF ) as the temperature increases. This stability can be attributed to the following two factors: 1) The highly reflective AuGe/Au mirror enhances the light absorption of the thin-film cell with a thin base layer, and 2) the good thermal dissipation of the Cu substrate reduces thermal degradation.
IEEE Transactions on Electron Devices 12/2011; · 2.32 Impact Factor
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ABSTRACT: This paper presents the In<sub>0.17</sub>Ga<sub>0.83</sub>As solar cell grown on misoriented GaAs substrate (2°- and 15<sup>°</sup>-off) by metalorganic chemical vapor deposition. The crystalline quality of the In<sub>0.17</sub>Ga<sub>0.83</sub>As solar cell is determined by X-Ray reciprocal space mapping (RSM). RSM results show that the crystalline quality of In<sub>0.17</sub>Ga<sub>0.83</sub>As solar cell grown on 2°-off GaAs substrate is better than that of 15°-off GaAs substrate. Moreover, the photovoltaic performance of In<sub>0.17</sub>Ga<sub>0.83</sub>As solar cell grown on 2°-off GaAs substrate is found to be better than that of In<sub>0.17</sub>Ga<sub>0.83</sub>As solar cell grown on a 15°-off GaAs substrate, because the In<sub>x</sub>Ga<sub>1-x</sub>As epilayer grown on 15°-off GaAs substrate shows a large strain relaxation in the active layer of the solar cell. A large strain relaxation causes high dislocation density at the initial active layer/In<sub>x</sub>Ga<sub>1-x</sub>As graded layer interface for the solar cell grown on 15°-off GaAs substrate. The effect of dislocation defects on the solar cell performance can be alleviated using the p-i-n structure as the epilayer grown on 15°-off GaAs substrate.
IEEE Journal of Quantum Electronics 12/2011; · 1.88 Impact Factor
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ABSTRACT: In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cells grown on GaAs substrates with different miscut angles via metalorganic chemical vapor deposition were utilized to study the effect of substrate orientation on solar cell efficiency. A p-n In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cell grown on a 2°-off GaAs substrate exhibited better conversion efficiency than one grown on a 15°-off GaAs substrate. The poor performance of the 15°-off In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cell could be attributed to the formation of high-density misfit dislocations through strain relaxation, thereby reducing the minority carrier lifetime. The conversion efficiency of a 15°-off In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cell was improved using a p-i-n structure. Using the p-i-n structure design, a 15°-off In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cell showed conversion efficiency close to or even better than that of a 2°-off In<sub>0.16</sub>Ga<sub>0.84</sub>As solar cell with the same structure.
IEEE Transactions on Electron Devices 10/2010; · 2.32 Impact Factor
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ABSTRACT: This letter presents performance comparison between a GaAs/mirror/copper thin-film solar cell and a conventional GaAs solar cell with a thick GaAs substrate. The GaAs thin-film solar cell was fabricated by transferring a GaAs solar cell onto a AuGe/Au mirror-coated copper substrate. With the aid of the excellent copper conductor, the thin-film solar cell exhibits significant improvement in both open-circuit voltage and short-circuit current density. The improved current-voltage ( I - V ) performance of the thin-film solar cell originates from the following two factors: reduced reverse saturation current by good heat dissipation of copper and enhanced light absorption by the highly reflective AuGe/Au mirror. The role of the mirror can further be verified in the measurement of external quantum efficiency (EQE) response where the thin-film solar cell exhibits a larger EQE response in the wavelength range of 700-900 nm than the conventional GaAs solar cell with the same active absorbing thickness.
IEEE Electron Device Letters 10/2009; · 2.85 Impact Factor
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ABSTRACT: Phosphorous-doped microcrystalline silicon (μc-Si) films were prepared using hot-wire chemical vapor deposition (HWCVD). Structural, electrical and optical properties of these thin films were systematically studied as a function of PH3 gas mixture ratio. We report recent results for p-type crystalline silicon-based heterojunction (HJ) solar cells using the HWCVD n-μc-Si film to form an n–p junction. The surface morphology of the crystalline Si substrate after hydrogen treatment was examined using atomic force microscopy. A transfer length method was used to modify the indium–tin–oxide (ITO) deposition parameters in order to reduce front ITO/n-μc-Si contact resistance. In our best solar cell sample (1 cm2) without any buffer layer, the conversion efficiency of 15.1% has been achieved with an open circuit voltage of 0.615 V, fill factor of 0.71 and short circuit current density of 34.6 mA/cm2 under 100 mW/cm2 condition. The spectral response of this cell will also be discussed.
Thin Solid Films.
