N, La Co-Doped TiO₂for Use in Low-Temperature-Based Dye-Sensitized Solar Cells

Abstract

In this survey, N, La co-doped TiO 2 nanocrystals are synthesized through simple sol-gel method. Results reveal that both elements of N and La are introduced successfully into the structure of TiO 2 and exist as the form of La (Ti-O-La) bonds, N (N-Ti-O) bonds and N (Ti-O-N) bonds by several characterization analysis, thereby resulting in the formation of new impurity energy level between the forbidden bands, and great enhancement of light absorption ability in visible light region. These resulting samples are fabricated for low-temperature-based dye-sensitized solar cells (DSSCs), and the highest temperature of the whole process is 120 • C. EIS, Bode plot and I-V analysis are employed to measure photovoltaic performance of DSSCs. The photoelectric conversion efficiency (η) of DSSCs with co-doped TiO 2 materials as the photoanode is 5.33%, and when compared to pure TiO 2 -based cell (4.02%), the η is increased by 32.6%. Dye-sensitized solar cells (DSSCs) have attracted a lot of research interest due to the low-cost, easy fabrication, good stability, and high photoelectric conversion efficiency.1 However, the traditional fabrication procedure of DSSCs requires not only the heavy FTO substrate, but also a high temperature calcination process at about 500 • C. These will limit the large area production and commercial application of DSSCs. In order to overcome these problems, flexible DSSCs with their incomparable advantages have attracted more interest of scientists, 2 compared with the traditional high temperaturebased DSSCs. By using the flexible substrate, the high temperature calcination process is not needed, which can save energy and reduce the production cost. More importantly, a wide range of flexible substrates can be applied in the fabrication of flexible DSSCs. Generally, the transparency of the solar cell substrate need to be more than 80%, and thus only FTO can be employed in the high temperature-based DSSCs. For the low temperature-based DSSCs, the substrate can involve FTO, ITO-PET (ITO-coated pol(ethylene terephthalate), ITO-PEN (ITO-coated polyethylene naphthalate), Ti foil and Ti meshes, [3][4][5] ZnO/Al thin film with high transmittance, 6 etc. It is believed that the cell based on the flexible substrate should possess the merits of being light weight, foldable and easy to carry, and thus can be used in portable electronic products. Furthermore, the cell preparation process is simple and suitable for industrial roll-to-roll mass production. It is known that the fabrication of photoanode at low temperature is essential for these flexible DSSCs. The paste employed for the generation of photoanode does not have to undergo a high temperature (about 500• C) annealing process, since no organic materials are introduced. After a slight agitation, the paste could be dried at low temperature(<150• C). Unfortunately, it is reported that the short-circuit current (J sc ) is low without the high temperature calcination process, which is the main reason for the poorer efficiency realized for the low temperatur...

Fast and Low-Temperature (70 °C) Mineralization of Inkjet Printed Mesoporous TiO2 Photoanodes Using Ambient Air Plasma

“…Even though the dip-coating method was used several times to deposit layers of sufficient thickness, the entire coating had to be processed in an oven at 120 °C for 1 h, which is quite a long time if roll-to-roll processing is envisaged. Similarly, Y. F. Jiang et al 11 used the doctor-blade technique to deposit an N−La codoped TiO 2 photoanode, which had to be further processed at 120 °C for 30 min to eliminate volatiles, still an extended period for convenient roll-to-roll processing. Silica has been successfully employed as a binder for passive photocatalytic coatings 12 and, despite its inherently insulating nature, it has proved useful for titania photoanodes as well.…”

Recent progress in one dimensional TiO2nanomaterials as photoanodes in dye-sensitized solar cells

“…The classification of dopants based on general electronic configuration falls into alkaline earth metals [94][95][96] , metalloids [97][98][99] , non-metals [100][101][102] , transition metals 103 , post-transition metals 104,105 and lanthanides [106][107][108] . Significant attempts were made for co-doping in which more than one dopant is introduced into the lattice for enhanced device performance [109][110][111] . Doping in TiO 2 lattice alters its phase, flat band potential, recombination rate, electron transport rate and dye adsorption capability 79 .…”

A review on spectral converting nanomaterials as a photoanode layer in dye‐sensitized solar cells with implementation in energy storage devices

“…Xie et al in 2012 presented the feasibility of luminescence conversion and RE ions as p‐type dopants leading to elevation of Fermi‐level of the oxide films, thus enhancing the photovoltage of the DSSCs. Therefore, solar conversion efficiency was enhanced in DSSCs containing RE ions as compared with DSSCs lacking RE ions. The authors reported that Tm 3+ /Yb 3+ ions act as luminescence medium and transfer infrared light into visible light through an upconversion luminescence process, which leads to improvement in incident light harvesting as well as enhanced photocurrent of RE‐doped DSSCs. In 2017, Fouad et al reported that with increasing Eu doping concentration optical absorption/fluorescence was enhanced and this resulted in an increase in the FWHM of peaks as well as photoconversion efficiency .…”

“…The authors reported that Tm 3+ /Yb 3+ ions act as luminescence medium and transfer infrared light into visible light through an upconversion luminescence process, which leads to improvement in incident light harvesting as well as enhanced photocurrent of RE‐doped DSSCs. In 2017, Fouad et al reported that with increasing Eu doping concentration optical absorption/fluorescence was enhanced and this resulted in an increase in the FWHM of peaks as well as photoconversion efficiency . It is observed that photoanode layer of Eu‐doped TiO 2 enhances efficiency as compared to undoped TiO 2 and this important property of doping plays an important role in altering the material for DSSCs to exhibit better performance . Figure represents the fabrication of DSSCs with Eu‐doped TiO 2 as photoanode, distinctly showing dye absorption, electrolyte reduction and oxidation, electron‐injection and conduction process …”