| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系所 === 103 === The semiconductor-insulator-semiconductor hetero-junction structure (SISHJS) comprising of a transparent conductive oxide (TCO) film directly deposited on the n-type Si substrates clad with a SiOx insulating layer were fabricated by pulsed laser deposi-tion (PLD). First, the SISHJS solar cells containing amorphous indium zinc oxide (a-IZO) and the thin SiOx layer grown by wet process were prepared. Such a device fabricated at low substrate temperature of 150°C exhibits a conversion efficiency of 2.2%, open-circuit voltage (Voc) of 0.24 V, short-circuit current density (Jsc) of 28.4 mA/cm^2 and fill factor (FF) of 33.6%. Analytical results indicated that the thickness and quality of the SiOx layer plays a decisive role in the performance of SIS solar cells. Accordingly, the dry thermal oxidation was employed to grow the SiOx layer and its thickness was further adjusted by varying the substrate temperature during PLD. It was found that, with the SiOx layer thickness about 1.8 to 2.0 nm obtained at sub-strate temperatures of 200 to 300°C, the device performance was improved to have Voc, Jsc, FF and conversion efficiency of 0.35 V, 28.6 mA/cm^2, 34.3% and 3.4%, respectively. The dry thermal method resulted in dense SiOx layer with less crystalline defects and, hence, the improved device performance. In order to further improve the conversion efficiency value of device, the interface trap density (Dit) at the a-IZO/SiOx interface has to be reduced. We ex-amined the influences of carrier density in the a-IZO layer on the photovoltaic (PV) characteristics of SISHJS devices by varying the In/(Zn+In) ratio while keeping the SiOx/Si part identical. The increase of In/(Zn+In) ratio in a-IZO layer apparently low-ered the Dit at the a-IZO/SiOx interface, presumably due to the charge compensation at the interface. The device exhibited the excellent SIS solar cells performance with Voc of 0.38 V, Jsc of 45.1 mA/cm^2, FF of 49.7% and conversion efficiency of 8.4% under the AM1.5 il-lumination condition.
This thesis study also found the TCO-based SISHJS is potentially sensitive to the lights with wavelengths ranging from near-infrared (NIR) to ultraviolet (UV) when the devices are irradiated by incident photons with energies above the optical energy band gap (Eg) of Si. The underlying mechanism for such a unique characteristic was attributed to the suppression of majority carrier tunneling resulted from the Schottky barrier established at interfaces of the SISHJS. The SIS photo-detectors made of the SISHJS exhibited the excellent photo-response of 35 AW^–1 and 6.15 AW^–1 under the illumination of 650-nm visible light and 365-nm UV light, respectively, with a quick photo-response time less than 80 msec.
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