Effect of seed layer on the growth of rutile TiO2 nanorod arrays and their performance in dye-sensitized solar cells

In order to improve the performance of TiO₂ photoanode-based dye sensitized solar cells (DSSCs), rutile TiO₂ nanorod arrays (NRAs) were grown on SnO₂:F (FTO) conductive glass coated with TiO₂ seed layer by a hydrothermal method. The TiO₂ seed layer was obtained by spin-coating titanium tetraisopropoxide (TTIP) isopropanol solution with concentration in the range of 0~0.075 M. Then the effect of the thin TiO₂ seed layer on the crystal structure and surface morphology of TiO₂ NRAs and the photoelectric conversion properties of the corresponding DSSCs were investigated. It is found that TiO₂ NRAs are vertically oriented, about 1.7 μm long and the average diameter is about 35 nm for the samples derived from TTIP in the range of 0.005~0.05 M, which are more uniform and better separated from each other than those without TiO₂ seed layer (average diameter 35~85 nm). The photoelectric conversion efficiency of DSSCs based on TiO₂ NRAs with TiO₂ seed layer is larger than that without TiO₂ seed layer. Typically, the energy efficiency of DSSCs obtained from the seed solution of 0.025 M TTIP is 1.47%, about 1.8 times greater than that without TiO₂ seed layer. The performance improvement is attributed to the thinner, denser and better oriented NRAs grown on seeded-FTO substrate absorbing more dye and suppressing charge recombination at the FTO substrate/electrolyte interface.     

Effect of growth time on morphology and photoelectrochemical performance of TiO2 nanorod arrays grown on transparent conducting substrates

TiO2 nanorod arrays (NRAs) were synthesized directly on the fluorine tin oxide (FTO) coated glass substrates by a facile hydrothermal route. The effects of growth time on the photoelectrochemical (PEC) properties of TiO2 NRAs are investigated. The samples synthesized for 4 h exhibit a photocurrent intensity of 0.37 mA/cm2 at the irradiation of Xe lamp and a bias of 0 V. As the growth time increases, the thickness and order degree of the NRAs are enhanced, but the photocurrent is reduced a lot. It might be associated with the hindering of a high background electron density in NRs due to the long-time hydrothermal reaction in acid environment. Moreover, the decline behavior is observed, which is attributed to the poor charge separation capacity of TiO2 array electrodes and could be suppressed efficiently by applying a suitable positive bias.     

Comparative study between CBD and SILAR methods for deposited TiO2, CdS,and TiO2/CdS core-shell structure

TiO₂, CdS, and TiO₂/CdS core–shell structures were deposited on fluorine-doped tin oxide (FTO)-coated glass substrate using chemical methods. TiO₂ thin films were prepared by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). SILAR was also utilized to deposit CdS film on TiO₂ thin film. The structural, surface morphology, and optical characteristics of FTO/TiO₂, FTO/CdS, and FTO/TiO₂/CdS core- shell structures were evaluated. The FTO/TiO₂ films produced by both methods conformed to anatase and rutile phase structures. Corresponding XRD pattern of the FTO/TiO₂/CdS sample exhibited one peak corresponding to hexagonal (101) for CdS. Scanning electron micrographs showed nanorod structures for the TiO₂ thin films deposited by CBD, contrary to the nanograin structure formed by SILAR. Optical results showed highly extended absorption edge to the visible region for the FTO/TiO₂/CdS structure deposited by the two methods. The TiO₂ thin films deposited by CBD exhibited higher absorption in the visible region than nanograined TiO₂ thin films deposited by SILAR because of the high surface area of the TiO₂ nanorod. Photoelectrochemical (PEC) properties of FTO/TiO₂, and FTO/TiO₂/CdS system were also examined. PEC behavior of FTO/TiO₂/CdS was compared with that of FTO/TiO₂ deposited by CBD and SILAR. The TiO₂ nanorod thin films deposited by CBD showed evidently enhanced PEC performance compared with nanograined TiO₂ thin films deposited by SILAR.     

CdS and PbS quantum dots co-sensitized TiO2 nanorod arrays with improved performance for solar cells application

In this paper, we report a novel CdS and PbS quantum dots (QDs) co-sensitized TiO₂ nanorod arrays photoelectrode for quantum dots sensitized solar cells (QDSSCs). TiO₂ film consisting of free-standing single crystal nanorods with several microns high and 90–100 nm in diameter were deposited on a conducting glass (SnO₂:FTO) substrate by hydrothermal method. Then CdS/PbS QDs were deposited in turn on TiO₂ nanorods by facile SILAR technique. The FTO/TiO₂/CdS/PbS, used as photoelectrode in QDSSCs, produced a light to electric power conversion efficiency (Eff) of 2.0% under AM 1.5 illumination (100% sun), which shows the best power conversion efficiency compared with single CdS or PbS sensitized QDSSCs. One dimension TiO₂ nanorod provides continuous charge carrier transport pathways without dead ends. The stepwise structure of the band edges favored the electron injection and the hole-recovery for both CdS and PbS layers in photoelectrode, which may gave a high electric power conversion efficiency. The facile preparation and low cost nature of the proposed method and structure make it has a bright application prospects in photovoltaic areas in the future.     

Synergistic Effect of Si Doping and Heat Treatments Enhances the Photoelectrochemical Water Oxidation Performance of TiO2 Nanorod Arrays

TiO₂ is a very promising photocatalytic material due to its merits including low cost, nontoxicity, high chemical stability, and photocorrosion resistance. However, it is also known that TiO₂ is a wide bandgap material, and it is still challenging to achieve high photocatalytic performance driven by solar light. In this paper, silicon‐doped TiO₂ nanorod arrays are vertically grown on fluorine‐doped tin oxide substrates and then are heat treated both in air and in vacuum. It is found that the silicon doping together with the heat treatment brings synergic effect to TiO₂ nanorod films by increasing the crystallinity, producing abundant oxygen vacancies, enhancing the hydrophilicity as well as improving the electronic properties. When used as photoanodes in photoelectrochemical water splitting, under the condition of AM 1.5G simulated solar irradiation and without using any cocatalysts, these nanorod films show photocurrent density as high as 0.83 mA cm^?2 at a potential of 1.23 V versus reversible hydrogen electrode, which is much higher than that of the TiO₂ nanorod films without doping or heat treating. The silicon‐doped TiO₂ nanorod array films described in this paper are envisioned to provide valuable platforms for supporting catalysts and cocatalysts for efficient solar‐light‐assisted water oxidation and other solar‐light‐driven photocatalytic applications.     

High-Performance Ultraviolet Photodetectors Enabled by van der Waals Schottky Junction Based on TiO2 Nanorod Arrays/Au-Modulated Ti3C2Tx MXene

Two-dimensional transition metal carbides and nitrides (MXenes) show tremendous potential for optoelectronic devices due to their excellent electronic properties. Here, a high-performance ultraviolet photodetector based on TiO₂ nanorod arrays/Ti₃C₂T_x MXene van der Waals (vdW) Schottky junction by all-solution process technique is reported. The Ti₃C₂T_x MXene modulated by the Au electrode increases its work function from 4.41 to 5.14 eV to form a hole transport layer. Complemented by the dangling bond-free surface of Ti₃C₂T_x, the Fermi-level pinning effect is suppressed and the electric-field strength of the Schottky junction is enhanced, which promotes charge separation and transport. After applying a bias of −1.5 V, the photovoltaic effect is favorably reinforced, while the hole-trapping mechanism (between TiO₂ and oxygen) and reverse pyroelectric effect are largely eliminated. As a result, the responsivity and specific detectivity of the device with FTO/TiO₂ nanorod arrays/Ti₃C₂T_x/Au structure reach 1.95 × 10⁵ mA W⁻¹ and 4.3 × 10¹³ cm Hz^1/2 W⁻¹ (370 nm, 65 mW cm⁻²), respectively. This work provides an effective approach to enhance the performance of photodetectors by forming the vdW Schottky junction and choosing metal electrodes to modulate MXene as a suitable charge transport layer.     

Periodic TiO2 Nanorod Arrays with Hexagonal Nonclose‐Packed Arrangements: Excellent Field Emitters by Parameter Optimization

Periodic TiO₂ nanorod arrays with hexagonal nonclose‐packed (hncp) arrangements are synthesized by pulsed laser deposition (PLD) using polystyrene colloidal monolayers as templates and with subsequent annealing in air. The hncp‐array formation is governed by in situ volume shrinkage of amorphous TiO₂ nanorods in the crystallizing process during annealing. The array periodicity can easily be tuned by different sphere sizes of the colloidal template, whereas the distance between neighboring nanorods can be controlled by altering the background gas pressure during the PLD process, at a given periodicity for the nanorod array. Parameter‐controlled growth is helpful for investigating and optimizing the parameter‐dependent field‐emission properties. The hncp nanorod array exhibits an enhanced field‐emission (FE) performance compared to both particle films and nanorod arrays with top aggregation. With an increase in periodicity of a hncp nanorod array, the field‐enhancement factor decreases and the turn‐on FE field increases. FE characteristics can be further enhanced by increasing the distance between adjacent nanorods while maintaining the same periodicity. The parameter‐optimized results suggest that the arrays with a smaller periodicity and a larger distance display the best FE performance and could be highly valuable for designing field‐emission devices based on these periodic nanorod arrays.     

Zero-valent nanophase iron and nitrogen co-modified titania nanotube arrays: Synthesis,characterization, and enhanced visible-light photocatalytic performance

We prepared nano-zero-valent iron (nZVI) and N co-modified TiO₂ (nZVI/N–TiO₂) nanotube arrays as an enhanced visible-light photocatalyst. The TiO₂ nanotube arrays were synthesized by electrochemical anodization of Ti foil in a two-electrode system. Amorphous TiO₂ nanotube arrays were immersed in ammonia and then annealed to produce crystalline N-doped TiO₂ (N–TiO₂) nanotube arrays. nZVI spheres were directly deposited on the N–TiO₂ nanotube arrays by borohydride reduction. The photocatalysts were characterized by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and electrochemical impedance spectroscopy (EIS). The environmental applicability and photocatalytic activity of the proposed nZVI/N–TiO₂ nanotube arrays were tested by phenol degradation in an aqueous system under UV and visible light irradiation. The phenol degradation rate constants of each sample under visible light irradiation were in the following order: nZVI/N–TiO₂ (k_obs=0.006 min⁻¹⁾>N–TiO₂ (k_obs=0.002 min⁻¹) ⪢ nZVI/TiO₂ (k_obs=0.0003 min⁻¹)>TiO₂ (k_obs=0.0001 min⁻¹). This result can be attributed to the synergistic effect of the N–TiO₂ nanotubes with lower energy band gap and the electron transfer from the conduction band (CB) of N–TiO₂ to nZVI spheres highly-dispersed on the N–TiO₂ for enhanced separation of photogenerated electrons and holes.     

TiO2 Coating for SnO2:F Films Produced by Filtered Cathodic Arc Evaporation for Improved Resistance to H+ Radical Exposure

Titanium dioxide thin films were deposited by filtered cathodic arc evaporation (FCAE) from a Ti target in an oxygen atmosphere onto (a) fluorine-doped tin oxide substrates SnO₂:F (FTO) and (b) glass microscope slides. The growth rate calculated from film thickness profilometry measurements was found to be approximately 0.8?nm/s. The films were highly transparent to visible light. x-Ray photoemission spectroscopy analysis of the Ti 2p electron binding- energy shift confirmed the presence of a TiO₂ stoichiometric compound. The results for the root-mean-square (RMS) surface roughness of the films deposited onto FTO substrates evaluated by atomic force microscopy suggested nanostructured film surfaces. When exposed to hydrogen plasma, TiO₂ films revealed insignificant changes in the optical spectra. The initial sheet resistance of the SnO₂:F layer was 14?Ω/sq. The deposition of the top TiO₂ layer (45?nm thick) over the FTO electrode resulted in an increase of the sheet resistance of 2?Ω/sq. In addition, the sheet resistance of the double-layer FTO/TiO₂ transparent conductive oxide (TCO) electrode increased by 1?Ω/sq as a result of H⁺ plasma exposure. Regardless of the TiO₂ film’s low conductivity, a thin protective layer could be coated onto FTO films (presumably 15?nm thick) due to their high transparency, offering high resistance to aggressive H⁺ plasma conditions. In this paper we show that ～50-nm-thick TiO₂ coating on FTO films provides sufficient protection against deterioration of transparency and conductivity due to hydrogen radical exposure.     

Binder-free MWCNT/TiO2 multilayer nanocomposite as an efficient thin interfacial layer for photoanode of dye sensitized solar cell

Multiwalled carbon nanotube/TiO₂ multilayer nanocomposite was successfully deposited on the fluorine-doped tin oxide (FTO) glass via layer-by-layer assembly technique to modify interfacial contact between the FTO surface and nanocrystalline TiO₂ layer as well as carbon nanotube/TiO₂ contacts in photoanode of dye sensitized solar cell. Using this approach, binder-free interfacial thin film was developed with nonagglomerated, well-dispersed MWCNTs on FTO and into TiO₂ matrix and with maximum covering of TiO₂ nanoparticles on MWCNTs. Introduction of MWCNTs/TiO₂ interfacial layer into the TiO₂ photoanode increased short circuit current density (J_sc) from 11.90 to 17.25 mA/cm² and open circuit voltage (V_oc) from 730 mV to 755 mV, whereas there was no notable change in the fill factor (FF). Consequently, power conversion efficiency (η) was enhanced from 5.32% to 7.53%, yielding a 41.5% enhancement. The results suggest that our simple strategy can integrate reduction of back electron reaction at FTO/TiO₂ interface with the effective charge transport ability of carbon nanotubes and possessing high surface area for efficient dye loading.     

The preparation of oxygen-deficient ZnO nanorod arrays and their enhanced field emission

Vertical and uniform zinc oxide (ZnO) nanorod arrays (NRAs) with sharp tips were fabricated on Zn substrate by a straightforward hydrothermal method without the assistance of seed layer, template or surfactant. Whereafter, the as-synthesized ZnO NRAs were successfully doped with oxygen vacancies by sodium borohydride (NaBH₄) solution reduction, aiming to generate donor energy levels below the conduction band. More importantly, the doped concentration of oxygen vacancies could be effectively controlled by adjusting the reduction temperature, and we have ultimately achieved the purpose of controllable tailoring the energy band structure of ZnO NRAs. As with design, the oxygen-deficient ZnO NRAs present a lower turn-on field of 0.67 V/μm, higher field enhancement factor of 64601 and better field emission stability. Such excellent FE performance of the as-prepared emitter should originate from the optimization of geometry, the efficient electron transport, as well as the decreased work function.     

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

High Areal Capacity Dendrite-Free Li Anode Enabled by Metal–Organic Framework-Derived Nanorod Array Modified Carbon Cloth for Solid State Li Metal Batteries

Li metal is one of the most promising anode materials for high energy density batteries. However, uncontrollable Li dendrite growth and infinite volume change during the charge/discharge process lead to safety issues and capacity decay. Herein, a carbonized metal–organic framework (MOF) nanorod arrays modified carbon cloth (NRA-CC) is developed for uniform Li plating/stripping. The carbonized MOF NRAs effectively convert the CC from lithiophobic to lithiophilic, decreasing the polarization and ensuring homogenous Li nucleation. The 3D interconnected hierarchal CC provides adequate Li nucleation sites for reducing the local current density to avoid Li dendrite growth, and broadens internal space for buffering the volume change during Li plating/stripping. These characteristics afford a stable cycling of the NRA-CC electrode with ultrahigh Coulombic efficiencies of 96.7% after 1000 h cycling at 2 mA cm⁻² and a prolonged lifespan of 200 h in the symmetrical cell under ultrahigh areal capacity (12 mAh cm⁻²) and current (12 mA cm⁻²). The solid-state batteries assembled with the composite Li anode, high-voltage cathode (LiNi_0.5Co_0.2Mn_0.3O₂), and composite solid-state electrolyte also deliver excellent cyclic and rate performance at 25 °C. This work sheds fresh insights on the design principles of a dendrite-free Li metal anode for safe solid-state Li metal batteries.     

Piezoelectric‐Effect‐Enhanced Full‐Spectrum Photoelectrocatalysis in p–n Heterojunction

Photoelectrochemical (PEC) water splitting offers a promising strategy for converting solar energy to chemical fuels. Herein, a piezoelectric‐effect–enhanced full‐spectrum photoelectrocatalysis with multilayered coaxial titanium dioxide/barium titanate/silver oxide (TiO₂/BTO/Ag₂O) nanorod array as the photoanode is reported. The vertically grown nanorods ensure good electron conductivity, which enables fast transport of the photogenerated electrons. Significantly, the insertion of a piezoelectric BaTiO₃ (BTO) nanolayer at the p‐type Ag₂O and n‐type TiO₂ interface created a polar charge‐stabilized electrical field. It maintains a sustainable driving force that attract the holes of TiO₂ and the electrons of Ag₂O, resulting in greatly increased separation and inhibited recombination of the photogenerated carriers. Furthermore, Ag₂O as a narrow bandgap semiconductor has a high ultraviolet–visible–near infrared (UV–vis–NIR) photoelectrocatalytic activity. The TiO₂/BTO/Ag₂O, after poling, successfully achieves a prominent photocurrent density, as high as 1.8 mA cm^?2 at 0.8 V versus Ag/Cl, which is about 2.6 times the TiO₂ nanorod photoanode. It is the first time that piezoelectric BaTiO₃ is used for tuning the interface of p‐type and n‐type photoelectrocatalyst. With the enhanced light harvesting, efficient photogenerated electron–hole pairs' separation, and rapid charge transfer at the photoanode, an excellent photoelectrocatalytic activity is realized.     

Tunable TiO2 films for high-performing transparent Schottky photodetector

We demonstrate the transparent Schottky photodetector of the configuration Cu/TiO₂/FTO unveiling superior photodetection properties. The improved performance of fabricated photodetector was ascribed to high quality rutile-nanocrystalline TiO₂ films with very high absorption coefficient (~6×10⁵ cm⁻¹) and excitonic localized states. The existence of such localized states in TiO₂ Schottky device offered fastest response time of 1.12 ms suggesting their application in fast switching photodetectors. In addition, the photodetectors showed high responsivity of the value 0.897 A/W and detectivity 4.5×10¹² Jones. This transparent TiO₂ design would provide a functional route for various photoelectric device applications.     

Anatase titania nanorods by pseudo-inorganic templating

A novel, facile and cost-effective single step aqueous sol–gel method for the synthesis of anatase TiO₂ nanorods without the assistance of structure-directing organic/inorganic templates is reported. We specifically demonstrate a pseudo-inorganic templating method using ammonium iron (III) sulfate. Highly thermal stable anatase TiO₂ nanorods were obtained using titanium oxysulfate and ammonium iron (III) sulfate as precursors. The structural, microstructural and chemical analyses of the nanorods synthesized, strongly supported the pseudo inorganic templating role of ammonium iron (III) sulfate on the formation of nanorod morphology. The materials have been characterized using different techniques such as TEM, XRD, BET surface area measurement, diffuse reflectance spectra and XPS. TEM study confirmed the rod shape of nano-anatase TiO₂, having a diameter in the range of 20–40 nm and a length of 100 nm. XPS investigation showed that along with Fe³⁺, nitrogen and sulfur were also been doped into the TiO₂ lattice from the single source dopant precursor ammonium iron (III) sulfate. Moreover, UV/vis diffuse reflectance spectra of nanorods showed red-shifts towards visible light and a corresponding decrease in band-gap energies consistent with an n-type doping of the anatase TiO₂ matrix. This aqueous sol–gel synthesis of anatase nanorod with pseudo inorganic templating explores the advantages of inexpensive precursors, control over the powder morphology and optical properties, and distribution of the dopants over TiO₂ at nano level due to homogeneous mixing of the precursors. Finally the photocatalytic analysis showed that the TiO₂ nanorod have two times higher activity than the commercially available Degussa P 25.     

Tailoring the surface morphology of TiO2 nanotube arrays connected with nanowires by anodization

Different surface morphologies of TiO₂ nanotube arrays were formed by anodization of Ti foils in various water-containing electrolytes at various voltages. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to investigate the morphology of TiO₂ nanowires. The results show that the morphology of TiO₂ nanowires is apparently influenced by viscosity of electrolytes and voltage. In this case, we introduce a detailed formation mechanism of nanowires that shows a strong relationship between the formation of TiO₂ nanowires and TiF₆²⁻ concentration. It was also found that TiO₂ nanowires are polycrystalline with anatase phase after annealing at 450 °C for 3 h.     

Solar Cells by Design: Photoelectrochemistry of TiO2 Nanorod Arrays Decorated with CdSe

One‐dimensional (1D) nanostructures of TiO₂ are grown directly on transparent, conductive glass substrate using hydrothermal/solvothermal methods. When employed as a photoanode in photoelectrochemical cells, the vertically aligned TiO₂ nanorod array exhibits slower charge recombination at electrolyte interface as compared to mesoscopic TiO₂ particulate film. Electrochemical deposition of CdSe onto TiO₂ nanorod array is carried out to extend absorption into visible light region. The role of CdSe‐sensitized, 1D rutile TiO₂ architecture in the solar cell design is discussed.     

Ti3+ Self‐Doped Dark Rutile TiO2 Ultrafine Nanorods with Durable High‐Rate Capability for Lithium‐Ion Batteries

Dark‐colored rutile TiO₂ nanorods doped by electroconducting Ti³⁺ have been obtained uniformly with an average diameter of ≈7 nm, and have been first utilized as anodes in lithium‐ion batteries. They deliver a high reversible specific capacity of 185.7 mAh g^?1 at 0.2 C (33.6 mA g^?1) and maintain 92.1 mAh g^?1 after 1000 cycles at an extremely high rate 50 C with an outstanding retention of 98.4%. Notably, the coulombic efficiency of Ti³⁺–TiO₂ has been improved by approximately 10% compared with that of pristine rutile TiO₂, which can be mainly attributed to its prompt electron transfer because of the introduction of Ti³⁺. Again the synergetic merits are noticed when the promoted electronic conductivity is combined with a shortened Li⁺ diffusion length resulting from the ultrafine nanorod structure, giving rise to the remarkable rate capabilities and extraordinary cycling stabilities for applications in fast and durable charge/discharge batteries. It is of great significance to incorporate Ti³⁺ into rutile TiO₂ to exhibit particular electrochemical characteristics triggering an effective way to improve the energy storage properties.     

High Efficiency Solid‐State Dye‐Sensitized Solar Cells Assembled with Hierarchical Anatase Pine Tree‐like TiO2 Nanotubes

A facile and effective method to prepare hierarchical pine tree‐like TiO₂ nanotube (PTT) arrays with an anatase phase directly grown on a transparent conducting oxide substrate via a one‐step hydrothermal reaction. The PTT arrays consist of a vertically oriented long nanotube (NT) stem and a large number of short nanorod (NR) branches. Various PTT morphologies are obtained by adjusting the water/diethylene glycol ratio. The diameter of the NTs and the size of the NR branches decreases from 300 to100 nm and from 430 to 230 nm, respectively, with increasing water content. The length of the PTT arrays could be increased up to 19 μm to significantly improve the charge transport and specific surface area. The solid‐state dye‐sensitized solar cells (ssDSSC) assembled with the 19 μm long PTT arrays exhibit an outstanding energy‐conversion efficiency of 8.0% at 100 mW/cm², which is two‐fold higher than that of commercially available paste (4.0%) and one of the highest values obtained for N719 dye‐based ssDSSCs. The high performance is attributed to the larger surface area, improved electron transport, and reduced electrolyte/electrode interfacial resistance, resulting from the one‐dimensional, well‐aligned structure with a high porosity and large pores.