| Summary: | 碩士 === 國立中興大學 === 精密工程學系所 === 98 === This thesis 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 is fabricated by transferring a GaAs solar cell onto a AuGe/Au mirror-coated copper substrate. The device performance of GaAs solar cell with different base layer thickness for thin-film and conventional solar cell will be discussed and compared. The base layer thickness leads the performance of solar cell and results in increased photocurrent. The copper substrate thickness of thin films solar cell are 50, 100, 150 and 200 μm, respectively. With the aid of the excellent copper conductor, the thin-film solar cell exhibits significant improvement in both open-circuit voltage (Voc) and short-circuit current (Jsc) density in one-sun AM 1.5G light source. 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. The device properties of conventional solar cell versus different working temperature show the degradation of cell performance for open circuit voltage and fill factor (FF) due to the degradation of bulk semiconductor material. The GaAs thin films solar cell significantly is improved temperature coefficient of FF by transferring onto a copper substrate. A combined analysis on dVoc/dT, dJsc/dT and dFF/dT, the degradation of the conversion efficiency for conventional GaAs solar cell is improved by the thin-film solar cell with thick copper sub (thickness is 200 μm). The dη/dT value of conventional GaAs solar cell can be alleviated from -0.0235 %/°C to -0.01077 %/°C.
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