Two-Stage Hydrothermal Growth of Long ZnO Nanowires for Efficient TiO₂ Nanotube-Based Dye-Sensitized Solar Cells

Abstract

Vertically aligned TiO 2 1-D nanostructures synthesized directly on transparent conducting oxide (TCO) have shown great promise to overcome the limitation of the random network of TiO 2 nanoparticles currently used in dyesensitized solar cells (DSCs). A promising process for synthesis of such structures is to first grow aligned ZnO nanowire arrays and then convert them to TiO 2 nanotubes. Growth of ZnO nanowires with a sufficient length and density but without fusion of their roots, however, remains challenging. In this paper, we investigate the dependence of wire density and aspect ratio on the temperature, concentrations of reagents, and seeding crystals used in a liquid-phase ZnO nanowire synthesis process. On the basis of the results of the investigation, we introduce a two-step hydrothermal process for synthesis of long and vertically aligned ZnO nanowire arrays, and demonstrate that, by dividing the wire growth process into two steps at two different temperatures and reducing Zn 2+ concentration, ZnO nanowires up to 20 μm long can be obtained without fusing their roots. The resulting ZnO nanowires can be converted into TiO 2 nanotubes, and DSCs fabricated using such TiO 2 nanotubes yield power conversion efficiencies up to 6.1%.

Three dimensional-TiO2 nanotube array photoanode architectures assembled on a thin hollow nanofibrous backbone and their performance in quantum dot-sensitized solar cells

“…Similar recombination resistances are observed for both samples. Despites the larger effective surface area of H-TiO 2 NFs, the recombination resistance does not become significantly 15 higher than the resistance observed for TiO 2 -NT. voltage, V app =0.57 V. Red solid line is the fit of the experimental data points using the previously described model for EIS analysis of QDSCs samples 7 .…”

“…Fig. 1(f) reveals that the spatially decorated ZnO NT arrays on TiO 2 NF have good 15 contact with the TiO 2 backbone. Furthermore, TEM image ( Fig.…”

“…15 The mesoscopic sensitized-solar cell is the emerging candidate in electrical power production though direct conversion of solar energy to electrical energy without green house effect. 1 Recently, quantum dot (QDs) semiconductors have attracted a great deal of 20 interest as sensitizers in mesoscopic sensitized solar cells.…”

“…One simple way to promote the interface surface area of the NT array is to extend their length, 15 however there exist a tradeoff between the NT length and mechanical stability. Therefore, assembling NT array on highly interconnected 3D fibrous backbone would be a more effective way for achieving high 70 electron transport channels in energy conversion devices.…”

Research Progress in Preparation and Applications of ZnO Nanowire/rod Arrays by Hydrothermal Method

“…the functional relationship between length of ZnO nanowire arrays and thickness of ZnO seed layer and (c) the functional relationship between length of ZnO nanowire arrays and preheating time [6] 面的粗糙度和结晶质量(图 11b), 进而影响 ZnO 纳米线 的长度和直径(图 11c Figure 15 Side-view SEM image of ZnO nanowire arrays prepared by two-step hydrothermal process [40] 由于制备 ZnO 纳米线阵列时会不断消耗生长液中 的溶质而阻碍纳米线的生长, 所以 2012 年 Chen 等 最近, 本课题组 [48] 首先将 0.0111 g 醋酸锌和 0.0060 g 的氢氧化钠溶解于 12 mL 甲醇溶液中, 超声 2 h 后形 成均匀的种子液; 然后在玻璃基底上旋涂种子液并加热 形成 ZnO 种子层, 再利用微加工技术构建出了微流控 器件(图 17a); 最后在 90 ℃条件下保持生长液的注入速 度为 15 μL/min, 在 6 h 内制备出了长度达到 11 μm 的 ZnO 纳米线阵列(图 17b), 纳米线阵列的制备过程如图 17c. 该方法避免了更新生长液的复杂操作 [11] , 进一步 减少了 ZnO 纳米线阵列的制备时间, 提高了纳米线的 生长效率 [37] .…”