Three-dimensional Graphene-Silicon Schottky Junctions to Enhance Stability and Performance of Photoelectrochemical Cells

• Main Authors: Che-Kuei Ku, 顧哲魁
• Other Authors: Chun-Wei Chen
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9w6mrx

碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 107 === Photoelectrochemical (PEC) water splitting has drawn lots of attention as an eco-friendly technology for renewable energy. Since 1976, silicon, whose band gap is smaller, and band edge position overlaps the potential of hydrogen evolution, has been widely used as the electrode in PEC devices. Recently, graphene, an atomic-layered carbon-based material with extraordinary properties, has been introduced to this field to form Schottky junction with silicon. The high efficiency of charge separation and passivation of graphene-silicon Schottky junction indeed enhanced the performance and stability of PEC devices. However, the high reflectivity of silicon substrates has been a big issue in harvesting solar energy. Therefore, how to solve the problem of reflectivity and improve the performance of devices is my thesis topic.At the beginning of my thesis, we try to build graphene-silicon Schottky junction on the anti-reflective pyramid silicon. With the introduction of the EVA transfer method, the quality and integrity of graphene are perfect on the pyramid silicon. The precise analyze, like SEM, AES, and STEM, prove that we successfully create the three-dimensional graphene-silicon Schottky junction on each part of the pyramid silicon. Next, this new epoch-making Schottky junction is utilized to improve the performance of PEC. Due to the increment of harvested incident light, the saturation current reaches 42.5 mA/cm2, and, after the deposition of Pt particles, the onset potential shifts positively to 0.3 V vs. RHE. Graphene layer protects the pyramid silicon very well after we finished a 30-hour-long measurement of stability. Moreover, the tunable morphology of deposited Pt on the graphene/pyramid-silicon is investigated, and we also hypothesize the intriguing mechanism. Due to these result, the three-dimensional graphene-silicon Schottky junction is a promising structure for future utilization of solar energy.