標題: Enhanced performance of dye-sensitized solar cells by an Al2O3 charge-recombination barrier formed by low-temperature atomic layer deposition
作者: Lin, Ching
Tsai, Feng-Yu
Lee, Min-Hsueh
Lee, Chia-Hua
Tien, Ta-Chang
Wang, Lih-Ping
Tsai, Song-Yeu
材料科學與工程學系
Department of Materials Science and Engineering
公開日期: 1-一月-2009
摘要: Al2O3 films are deposited conformally and uniformly by atomic layer deposition (ALD) at 150 degrees C throughout the surface of the nanoporous TiO2 electrode of dye-sensitized solar cells (DSSCs) to serve as charge recombination barriers (CRB). The self-limiting film growth of ALD enables detailed analysis of the thickness dependence of the CRB effects on the DSSCs, revealing the optimal Al2O3 CRB thickness to be that produced by 1 ALD cycle (nominal thickness - 0.1 nm), at which the CRB increases the power conversion efficiency (PCE) of the DSSCs by 14% (to up to 7.8% PCE). Above 1 cycle, the ALD films excessively raise the Fermi level of the TiO2 electrode surface, as determined by ultraviolet photoelectron spectroscopy (UPS), so as to block electron injection at the dye-to-TiO2 heterojunction and to cause significant degradation in the DSSC performance. Instead of its nominal 0.1 nm thickness, the 1-cycle ALD film has an effective CRB thickness of 0.3 nm because of steric hindrance among the ALD precursor molecules and the dye molecules, as analyzed by a graphical model. The optimal thickness of the ALD Al2O3 CRB is considerably thinner than the 0.9-2.5 nm reported for Al2O3 CRB formed by conventional sol-gel processes, but it should better reflect the true value, considering the better infiltrating capability and finer thickness resolution of the ALD films. The low temperature and fine thickness control of the ALD process will broaden the utility of CRB.
URI: http://dx.doi.org/10.1039/b819337a
http://hdl.handle.net/11536/149779
ISSN: 0959-9428
DOI: 10.1039/b819337a
期刊: JOURNAL OF MATERIALS CHEMISTRY
Volume: 19
起始頁: 2999
結束頁: 3003
顯示於類別:期刊論文