Laser Sintering of TiO2 Films for Flexible Dye-Sensitized Solar Cells

Abstract

In this study, laser sintering of TiO2 nanoparticle films on plastic substrates was conducted in order to improve the incident photon-to-electron conversion efficiency (IPCE) of flexible dye-sensitized solar cells (DSCs). Lasers with different wavelengths (355 nm and 1064 nm) were used to process the TiO2 electrodes. With an optimized processing parameter combination, the 1064 nm laser can sinter 13 μm thick TiO2 films uniformly, but the uniform sintering cannot be achieved by the 355nm ultraviolet (UV) laser, since the films possess a high absorption ratio at 355 nm. The experimental results demonstrate that the near-infrared laser sintering can enhance the electrical connection between TiO2 nanoparticles without destroying the flexible plastic substrate, reduce the transmission impedance of electrons and increase the absorption rate of incident light. Furthermore, the charge collection efficiency, fill factor, and short-circuit current have all been improved to some extent, and the solar conversion efficiency increased from 4.6% to 5.7%, with an efficiency enhancement reaching 23.9%.

Extremely Sensitive SERS Sensors Based on a Femtosecond Laser-Fabricated Superhydrophobic/-philic Microporous Platform

“…Surface-enhanced Raman scattering (SERS) is a phenomenon in which Raman signals can be significantly enhanced on well-designed plasmonic materials or structures. − Two main primary mechanisms, electromagnetic (EM) enhancement and chemical (CM) enhancement, are believed to be responsible for Raman signal enhancement. − The latter mechanism induced by the localized surface plasmon resonance is universally accepted. , Considering the advantages of noninvasive, fast-detection, and label-free means, this technology is one of the most promising candidates for detecting highly low-concentration analytes. − It has been extensively applied in explosive detection, , precancer diagnosis, food safety, − forensic analysis, etc. In these cases, the target molecules are usually randomly dispersed in highly diluted solutions with concentrations as low as the pico/femtomolar level.…”

Transmittance of TiO2 Nanoparticle-based Films Deposited by CO2 Laser Heating

“…Titanium dioxide (TiO2) is known to possess excellent thermophysical, mechanical, and optical properties 1,2 , but it is difficult to directly deposit TiO2 nanoparticles (NPs) into large two-dimensional (2D) films or three-dimensional (3D) microstructures, such as patterned and periodic microstructures. A new laser manufacturing technique; called the nanoelectrospray laser deposition technique (NELD) process, is developed for simultaneously patterning and sintering semiconductor and metal nanoparticles to deposit 2D and 3D micro-nanostructures for different applications [3][4][5] .…”

“…TiO2 crystallizes in three structures, which are anatase (tetragonal, space group 𝐼4 1 𝑎𝑚𝑑 ⁄ , 𝜌 = 3.89 𝑔 𝑐𝑚 2 ⁄ ), rutile (tetragonal, space group 𝑃42 𝑚𝑛𝑚 ⁄ , 𝜌 = 4.25 𝑔 𝑐𝑚 2 ⁄ ), and brookite (orthorhombic, space group 𝑃𝑐𝑎𝑏, 𝜌 = 4.12 𝑔 𝑐𝑚 2 ⁄ ) 12 . The thermal transformation from anatase to rutile phase; i.e., the growth process of the TiO2 films, depends on the grain boundary concentration, particle packing and size, defect concentration, and annealing temperature 1,12 . As a bulk material, rutile is the stable phase of TiO2 under ambient conditions, whereas anatase and brookite are metastable and can transform to rutile under thermal treatment (in an oven) 11 or laser heating 2 .…”

Emergence and Evolution of Crystallization in TiO2 Thin Films: A Structural and Morphological Study

“…This exciting and rich set of material properties has made TiO 2 a valuable candidate for applications in many fields, as well as for fundamental science investigations. To date, the market demand on TiO 2 -based devices for photocatalysis [1][2][3][4], sensors [5,6], optical reflective coatings for highly innovative 2 of 18 applications [7,8] (innovative mirrors for gravitational wave interferometers, among the others [9][10][11][12]), solar cells [13][14][15], metal insulator semiconductor industry [16], self-cleaning application [17][18][19], water purification processes [20], has been systematically growing, especially for thin films and nanostructures. In addition, a constant effort has been made in setting up reliable computational techniques, mainly based on density functional theory (DFT), to predict and describe the properties of TiO 2 , not only in its crystalline forms, but also in the amorphous phase, as well as to simulate the amorphous to crystalline phase transition [21][22][23].…”