CdS-ZnO奈米異質結構之製備與其載子分離特性

Abstract

由兩個半導體間能階之差異，因具有光誘發電子電洞對分離之特性，而廣泛運用於光電轉換用途，包含太陽能電池、光催化反應或分解水產生氫氣等。本實驗是利用水熱法製備CdS奈米棒後，再一次利用水熱法將ZnO奈米粒子修飾於CdS奈米棒表面，以形成CdS/ZnO奈米異質結構，藉由控制水熱中去離子水的含量，可以控制其修飾於CdS奈米棒表面之ZnO奈米粒子數量。由於CdS與ZnO間能帶結構為Type-II，使光激發電子會傾向於從CdS傳遞至ZnO，而電洞則傾向於從ZnO傳遞至CdS，以達成電子電洞對的分離。 由穩定態光致螢光光譜(steady-state photoluminescence)的測量結果確定經由ZnO奈米粒子修飾之CdS奈米棒可有效達到載子分離之特性，將其於可見光下作RhB降解光催化反應，可以得到其加入4mL水製備出的CdS/ZnO 具有最佳光觸媒效果。CdS-ZnO奈米異質材料在太陽光下亦有良好之光催化效果，相較於商用CdS而言，則其應用於光電裝置或氣體偵測有優良的效果。且由重覆照光光催化測試可知其穩定性較純CdS高。由此研究製備出之ZnO奈米粒子修飾於CdS奈米棒，預期可在光催化或水分解有良好效果

Due to the photo-induced charge carrier separation property, Semiconductor-semiconductor nanoheterostructures have been applied in many photoeletronic conversion processes, such as photovoltaics, photocatalysis, and water splitting. In this work, we successfully use two-step solvothermal method to synthesize CdS-ZnO nanoheterostucture. One solvothermal method use to prepare CdS nanorods, and the other solvothermal method use to be decorated ZnO nanoparticles on CdS nanowires. By modulating the ratio of water, the amount of ZnO nanoparticles which be decorated on CdS nanorods can be controlled. Because of CdS-ZnO band structure type is type-II, the photoexicited electrons of CdS would preferentially transfer to ZnO, and the photogenerate holes of ZnO would transfer to CdS, which achieve charge separation. The result of steady-state photoluminescence analysis confirms the enhancement in charge separation efficiency for CdS-ZnO nanoheterostuctures. Among the different samples, CdS-ZnO nanoheterostuctures which synthesize by 4mL water show the most significant charge separation efficiency, which may find the potential application in relevant photocatalytic reaction including photoexcited electron storage and water splitting.