Preparation of Iron(Ⅲ) Oxide Thin Films for Photoelectrochemical Cell
Date Issued
2005
Date
2005
Author(s)
Liu, Huei-Yu
DOI
zh-TW
Abstract
Compared to silicon, iron oxide can absorb sunlight in the lower wavelength region. It is one of the candidates which can combine with silicon to form ideal multijunction electrode with higher solar-efficiency than the single band-gap silicon electrode. Therefore, the preparation of Fe2O3 thin films and the characterization of their photoelectrochemical properties were carried out in this research. The films were mainly prepared from sol-gels by dip-coating technique, and were compared with that by sputtering technique. It was found that the pretreatment of substrates would be a significant key to the success of smooth film surface (without apparent cracks) from the dip-coating. Due to poor affinity between substrate (ITO glass) and sol-gel, a process (rinsing the substrate in methanol and drying in air at 60 ℃) has been developed in this study, which is sufficient to enhance the affinity. Moreover, we also observed that different electrolytes and morphologies have significant effects on the performance of photocurrents.
In order to increase the photocurrent, the effect of doping Si4+ or Ti4+ into the iron oxide film was studied. Either Si4+ or Ti4+ was added into the sol-gel solution and the resulted films were calcined at 700 ℃. It was found that owing to the larger difference between atomic sizes of Si4+ and Fe3+, the addition of Si4+ resulted in the distortion of iron oxide lattice. Therefore, the doping of Si4+ cannot improve the performance of thin films, but the doping of Ti4+ can.
Similar to the iron oxide pellets or particles, the films prepared from dip-coating possessed n-type semiconductor property. However, it was found in this research that the films prepared from the oxygen sputtering process possessed p-type property. It suggests that oxygen molecules were inserted between the framework of iron oxide during sputtering. The electrons would be trapped by these O2 molecules, and leaving holes in valence band which led the formation of p-type semiconductor.
Subjects
氧化鐵
多重能隙
光分解水
溶膠凝膠法
摻雜
基材前處理
介面能帶變化
P-type光電流
Iron oxide
Water splitting
Multijunction
Photoelectrolysis
Sol-gel technique
Substrate pretreatment
Interface change
Doping
P-type photocurrent
SDGs
Type
thesis
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