Effect of Au nano-particles on TiO2 nanorod electrode in dye-sensitized solar cells

Recent progress in one dimensional TiO2 nanomaterials as photoanodes in dye-sensitized solar cells

Exploiting the vast possibilities of crystal and electronic structural modifications in TiO2 based nanomaterials creatively attracted the scientific community to various energy applications. A dye sensitised solar cell, which converts photons into electricity, is considered a viable solution for the generation of electricity. TiO2 nanomaterials were well accepted as photoanode materials in dye-sensitized solar cells, and possess non-toxicity, high surface area, high electron transport rates, fine tuneable band gap, high resistance to photo corrosion and optimum pore size for better diffusion of dye and electrolyte. This review focuses on various aspects of TiO2 nanomaterials as photoanodes in dye-sensitized solar cells. TiO2 photoanode modification via doping and morphological variations were discussed in detail. The impact of various morphologies on the design of TiO2 photoanodes was particularly stressed.

Polyaniline-Layered Rutile TiO2 Nanorods as Alternative Photoanode in Dye-Sensitized Solar Cells

In this paper, dye-sensitized solar cell (DSSC) performance of the less explored polymorph of TiO₂, rutile, has been explored, and its performance has been modified with polyaniline (PANI) wrapping on the surface. For this purpose, highly crystalline rutile nanorods have been synthesized without any growth-directing substrates, employing a hydrothermal treatment. Further, to understand the phase composition and morphology, the synthesized nanorods and PANI-layered nanorods have been characterized through various physicochemical methods. The synthesized rods were implemented as photoanode material for DSSCs which exhibited a photoelectric conversion efficiency (PCE) of 4.28% with a high open-circuit voltage (V _OC) of 0.84 V which is highly superior to DSSC with Degussa P25 (PCE = 3.95%) TiO₂ nanoparticles. The resultant PCE of the nanorods was further enhanced to 6.23% on in situ deposition of PANI which acts as an electron-transporting layer. Introduction of conducting PANI over the rutile rod was explored as a new concept to improve the performance of photoanode material besides conventional TiCl₄ treatment or scattering layer deposition.

Enhanced light-harvesting by plasmonic hollow gold nanospheres for photovoltaic performance

A 'sandwich'-structured TiO₂NR/HGN/CdS photoanode was successfully fabricated by the electrophoretic deposition of hollow gold nanospheres (HGNs) on the surface of TiO₂ nanorods (NRs). The HGNs presented a wide surface plasmon resonance character in the visible region from 540 to 630 nm, and further acted as the scatter elements and light energy 'antennas' to trap the local-field light near the TiO₂NR/CdS layer, resulting in the increase of the light harvesting. An outstanding enhancement in the photochemical behaviour of TiO₂NR/HGN/CdS photoanodes was attained by the contribution of HGNs in increasing the light absorption and the number of electron-hole pairs of photosensitive semiconductors. The optimized photochemical performance of TiO₂NR/HGN/CdS photoanodes by using plasmonic HGNs demonstrated their potential application in energy conversion devices.

Plasmonically enhanced metal-insulator multistacked photodetectors with separate absorption and collection junctions for near-infrared applications

Plasmonically enhanced metal-insulator-metal (MIM) type structures are popular among perfect absorbers and photodetectors in which the field enhancement (for increased absorption) mechanism is directly coupled with collection (photocurrent) processes. In this work we propose a device structure that decouples absorption and collection parts for independent optimization. Double-stacked MIM (i.e. MIMIM) photodetectors operating in the near-infrared (NIR) spectrum up to 1200 nm wavelength are demonstrated. In the absorbing MIM (at the top side), we have used Silver nanoparticles resulting from dewetting, yielding a very low reflection of 10% for the most part of the 400 to 1000 nm wavelength range. An unconventional plasmonic material, Chromium, exhibits an absorption peak of over 80% at 1000 nm. The complete device has been fabricated and the photo-collection tunneling MIM (at the bottom) suppresses the leakage current by metal workfunction difference. An optimized stack consisting of Silver – Hafnium Oxide – Chromium – Aluminum Oxide – Silver nanoparticles (from bottom to top) yields a dark current of 7 nA and a photoresponsivity peak of 0.962 mA/W at 1000 nm and a full width at half maximum of 300 nm, while applied bias is 50 mV and device areas are 300 μm × 600 μm.

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells

In the present investigation, gold-silver@titania (Au-Ag@TiO₂) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au-Ag incorporated TiO₂ photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO₂ photoanode (2.22%) under full sunlight illumination (100 mW cm^-2, AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au-Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO₂ was found to be Au₇₅-Ag₂₅. This was reflected in the femtosecond transient absorption dynamics in which the electron-phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO₂/Au₇₅:Ag₂₅, compared to 2.38 ps for free Au and 4.02 ps for TiO₂/Au₁₀₀:Ag₀. The slower dynamics indicates a more efficient electron-hole separation in TiO₂/Au₇₅:Ag₂₅ that is attributed to the formation of a Schottky barrier at the interface between TiO₂ and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au-Ag@TiO₂ plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs.

Facile synthesis of Au@TiO2 nanocomposite and its application as a photoanode in dye-sensitized solar cells

Au@TiO₂ nanocomposite materials were synthesized by a facile one-step chemical reduction method and employed as photoanodes in dye-sensitized solar cells.