有效使用太陽能最近幾年成為各國研究發展的重點項目之一，無論是將太陽能直接轉換成熱能、 電能，或者是將太陽能轉換成化學能，皆需要一適當介質吸收太陽能，並且有效率的將其轉變成另一 形式的能量儲存。使用半導體光觸媒將太陽能轉換成化學能儲存是綠色生產的方式之一，以光分解水 為例，若半導體材料具有適當的能隙值、導帶及價帶的位置，光生載子便具有氧化與還原的能力與電 解質的物種進行反應，產生氧氣與氫氣。這種光化學/光電化學系統的效率，理想的狀況下，能隙值約 2.3 eV 的光觸媒，太陽光產氫效率可以達到10%。然而實際的效率遠低於此數值，其原因不外乎( 1 ) 光 生載子的分離效率差，( 2 ) 載子傳輸的有效距離短，( 3 ) 半導體光學吸收度低與元件吸光面積小，以 及( 4 ) 界面反應動力慢等。此計畫我們將使用較為綠色的噴塗製程，先減少前驅物使用量；並且利用 不同薄膜半導體間的能帶位置及性質，製備異質結構的薄膜半導體。使用薄膜內部驅動力來促進電子 -電洞分離效率，進而提升其光電轉化率，讓半導體效能提升以及利用此異質結構的薄膜半導體來探討 光電化學系統的載子傳輸機制。 ;Utilize the solar energy efficiently is one of the most important tasks for every country. No matter whether the solar energy is transformed into electricity, heat or chemical energy, a suitable medium to absorb and store the solar energy is required. One of the green processes to transform solar energy into chemical energy is to use semiconductor photocatalyst. Take water splitting for example, when the semiconductor has a suitable band gap, and right conduction band and valence band edges, the excited carriers gain enough potential to oxidize/reduce water and species presented in the electrolyte. Hydrogen and oxygen then can be produced without any CO2 emission and hazardous waste. In the ideal condition, the hydrogen production efficiency can reach 10% with the semiconductor of the band gap of 2.3 eV. Unfortunately, the real efficiency is far below this value. The reasons are the following: 1. low excited carrier separation, 2. short carrier diffusion length, 3. the small absorption/specific surface area, and 4. the slow reaction rate of the interface. In this proposed research, our approach involves the development of green pyrolysis to deposit semiconductor thin films, and generate homo- and heterojunction to create p-n junction. Based on our previous studies, different band positions and conductivity types of semiconductor (n-type and p-type) can be used as the model system, to improve the electron-hole separation, and to investigate the carrier transfer mechanism.
