Tien, T.-C.T.-C.TienPan, F.-M.F.-M.PanWang, L.-P.L.-P.WangLee, C.-H.C.-H.LeeTung, Y.-L.Y.-L.TungTsai, S.-Y.S.-Y.TsaiLin, C.C.LinFENG-YU TSAIChen, S.-J.S.-J.Chen2020-05-122020-05-122009https://scholars.lib.ntu.edu.tw/handle/123456789/491238Low-temperature (∼150 °C), atomic-layer-deposited Al 2O3 films on nanoporous TiO2 electrodes of dye-sensitized solar cells (DSSCs) were investigated using electron spectroscopy. The power conversion efficiency (PCE) of the DSSCs was increased from 5.7% to 6.5%, an improvement of 14%, with one monolayer of Al 2O3 with a thickness of ∼0.2nm. The formation of Ti-O-Al(OH)2 and interfacial dipole layers exhibited a strong influence on the work function of the Al2O3 over-layers, while the thicker Al2O3 over-layers caused the values of valence band maximum and band gap to approach the values associated with pure Al2O3. A work function difference (ΔΦ A-T) of 0.4eV and a recombination barrier height (ε RB) of 0.1eV were associated with the highest PCE achieved by the first monolayer of the Al2O3 layer. Thicker Al 2O3 over-layers, however, caused significant reduction of PCE with negative ΔΦT-A and increased interfacial energy barrier height (*εIB) between the N719 dyes and TiO2 electrodes. It was concluded that the PCE of the DSSCs may correlate with ΔΦA-T, εRB, and *εIB resulting from various thicknesses of the Al2O3 over-layers and that interfacial reactions, such as the formation of Ti-O-Al(OH)2 and dipole layers, play an important role in determining the interfacial energy levels required to achieve optimal performance of dye-sensitized TiO2 solar cells. © 2009 IOP Publishing Ltd.[SDGs]SDG7Atomic layer deposited; Band gaps; Barrier heights; Dye sensitized; Dye-Sensitized solar cell; Dye-sensitized solar cells; Interfacial dipole layers; Interfacial reactions; Low temperatures; N719 dye; Nanoporous TiO; Optimal performance; Power conversion efficiencies; Pure Al; TiO; Valence-band maximums; Work-function difference; Atoms; Conversion efficiency; Electrodes; Electron spectroscopy; Interfacial energy; Monolayers; Phase interfaces; Photoelectrochemical cells; Photovoltaic cells; Solar cells; Solar energy; Work function; Aluminum; aluminum oxide; dye; titanium dioxide; article; dipole; electrode; energy; nanopore; priority journal; spectroscopy; thicknessjournal article10.1088/0957-4484/20/30/3052012-s2.0-67651146667https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651146667&doi=10.1088%2f0957-4484%2f20%2f30%2f305201&partnerID=40&md5=ccc7f9149cf45ffba089a951f3b50312