Successful Growth of TiO2 Nanocrystals with {001} Facets for Solar Cells

Abstract

The growth of nanocrystals (NCs) from metal oxide-based substrates with exposed high-energy facets is of particular importance for many important applications, such as solar cells as photoanodes due to the high reactivity of these facets. The hydrothermal method remains a current trend for the synthesis of metal oxide nanostructures in general and titanium dioxide (TiO2) in particular since the calcination of the resulting powder after the completion of the hydrothermal method no longer requires a high temperature. This work aims to use a rapid hydrothermal method to synthesize numerous TiO2-NCs, namely, TiO2 nanosheets (TiO2-NSs), TiO2 nanorods (TiO2-NRs), and nanoparticles (TiO2-NPs). In these ideas, a simple non-aqueous one-pot solvothermal method was employed to prepare TiO2-NSs using tetrabutyl titanate Ti(OBu)4 as a precursor and hydrofluoric acid (HF) as a morphology control agent. Ti(OBu)4 alone was subjected to alcoholysis in ethanol, yielding only pure nanoparticles (TiO2-NPs). Subsequently, in this work, the hazardous chemical HF was replaced by sodium fluoride (NaF) as a means of controlling morphology to produce TiO2-NRs. The latter method was required for the growth of high purity brookite TiO2 NRs structure, the most difficult TiO2 polymorph to synthesize. The fabricated components are then morphologically evaluated using equipment, such as transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), electron diffraction (SAED), and X-ray diffraction (XRD). In the results, the TEM image of the developed NCs shows the presence of TiO2-NSs with an average side length of about 20–30 nm and a thickness of 5–7 nm. In addition, the image TEM shows TiO2-NRs with diameters between 10 and 20 nm and lengths between 80 and 100 nm, together with crystals of smaller size. The phase of the crystals is good, confirmed by XRD. The anatase structure, typical of TiO2-NS and TiO2-NPs, and the high-purity brookite-TiO2-NRs structure, were evident in the produced nanocrystals, according to XRD. SAED patterns confirm that the synthesis of high quality single crystalline TiO2-NSs and TiO2-NRs with the exposed {001} facets are the exposed facets, which have the upper and lower dominant facets, high reactivity, high surface energy, and high surface area. TiO2-NSs and TiO2-NRs could be grown, corresponding to about 80% and 85% of the {001} outer surface area in the nanocrystal, respectively.

Nanostructured thin films of TiO2 tailored by anodization

“…These characteristics fulfill the technical requirements, such as a glass substrate, nanometric pore size, length range, preferred orientation, transmittance, energy gap and wet contact angle, that make the achieved nanostructured TiO 2 thin films, potential candidates for the electron transport layers in hybrid perovskite solar cells. In addition, the results of this work open the possibility to prepare, at a low-cost, TiO 2 in thin film form, with a specific nanostructure, on diverse substrates relevant for particular applications (as the mentioned in references [6,7] and [12][13][14][15][16]).…”

“…3.37 ± 0.02 eV, for the 3 to 9 min samples, is suitable for HPSC applications[41]. These values are higher than in bulk TiO 2 (3.2 eV[13,40,44]), but within the expected range for TNS (∼3.3-3.43 eV[2,[45][46][47][48][49][50]). Table…”

“…The physical-chemical properties of TiO 2 have placed it as the preferred material for diverse applications, over other semiconductors as WO 3 , ZrO 2 , BiVO 4 , Fe 2 O 3 and NaTaO 3 [1]. Performance of such applications can be enhanced by the use of mesoporous and/or TiO 2 nanostructures in the anatase phase (TNS), as in biomedical implants [2], water and air remediation [3][4][5], gas sensors [6,7], degradation of dyes and pharmaceuticals [8,9], ceramic membranes [10], drug delivery and tissue engineering [11], photoelectrochemical cells [12], dyesensitized solar cells [13], supercapacitors [14] and Li-ion batteries [15]. TNS can also be used as the electron transport layer (ETL) in hybrid perovskite solar cells (HPSC) to increase the efficiency [16].…”

A Theoretical Insight into the Physical Characteristics of Double Perovskite Rb2TlInBr6 for Renewable Energy Applications

“…It is essential to assess the capabilities of materials and their inherent advantages in order to properly understand their technical applications, such as the fabrication of solar panels, photonic DOI: 10.1002/crat.202300329 sensors, thermoelectric generators, etc., [1] The double perovskite compounds have been identified as compatible materials in many practical applications because of their extraordinary properties. [2][3][4][5] Metallicity, halfmetallicity, ferromagnetism, photovoltaics, magneto-electricity, and photocatalytic are only a few of the intriguing physical characteristics that the double perovskites exhibit. [4,6] Due to their remarkable energy-harvesting abilities, these materials are currently finding use in optoelectronic and thermoelectric applications.…”

Fluoride Removal Using Nanofiltration-Ranged Polyamide Thin-Film Nanocomposite Membrane Incorporated Titanium Oxide Nanosheets

“…(a) TEM image of the TiO2 NSs and (b) simulated MountainsMap1 software of TEM image of the TiO2 NSs, Figure S2. Magnified HRTEM image of an NSs Reference [ 65 ] is cited in Supplementary Materials.…”