Mesh‐Shaped Nanopatterning of Pt Counter Electrodes for Dye‐Sensitized Solar Cells with Enhanced Light Harvesting

A facile process to produce large‐area platinum (Pt) counter electrode platforms with well‐arrayed, mesh‐shaped nanopatterns using commercially available TiO₂ paste and poly(dimethyl siloxane) (PDMS) nanostamps is presented. The process involves mesh‐shaped (200 nm × 200 nm) nanopatterning of a TiO₂ scaffold onto a fluorine‐doped tin oxide (FTO) substrate, followed by Pt sputtering. The structure and morphology of the counter electrodes are characterized by a field emission scanning electron microscope (FE‐SEM) and an atomic force microscope (AFM). Solid‐state dye‐sensitized solar cells (ssDSSCs) fabricated with these mesh‐shaped Pt counter electrodes showed an efficiency of 7.0%. This is one of the highest efficiencies observed for N719 dye and is much higher than that of devices with non‐patterned, thermally deposited electrodes (5.4%) or non‐patterned, sputtering deposited electrodes (5.7%). This improvement is attributed to enhanced light harvesting and a greater surface area and has been confirmed by incident photon‐to current efficiency (IPCE), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) measurements.     

Atomic Layer Deposition of Highly Transparent Platinum Counter Electrodes for Metal/Polymer Flexible Dye‐Sensitized Solar Cells

Atomic layer deposition (ALD) is used to deposit Pt nanoparticles at low temperature (25–150 °C) to fabricate highly transparent counter electrodes (CEs) for flexible dye‐sensitized solar cells (DSCs). The Pt nanoparticles (NPs) are deposited for different number of ALD cycles on indium tin oxide (ITO)/polyethylene naphthalate (PEN) substrates. Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM) are used to assess the Pt NP loading, density, and size. There is a trade‐off between transparency and catalytic activity of the CE, and the best cell performances of back‐side‐illuminated DSCs (≈3.7% efficiency) are achieved for Pt ALD at temperatures in the range of 100–150 °C, even though deposition at 25 °C is also viable. The best cell produced with ALD platinized CE (100 cycles at 100 °C) outperforms the reference cells fabricated with electrodeposited and sputtered Pt CEs, with relative improvements in efficiency of 19% and 29%, respectively. In addition, these parameters are used to fabricate a large area CE for a sub‐module (active area of 17.6 cm²), resulting in an efficiency of 3.1%, which demonstrates the scalability of the process.     

Bifunctional Moth‐Eye Nanopatterned Dye‐Sensitized Solar Cells: Light‐Harvesting and Self‐Cleaning Effects

A nanopatterning technique using nanostamps that provides a facile process to create a nature‐inspired moth‐eye structure achieving high transmittance in the visible range as well as a self‐cleaning effect is reported. Commercially available perfluoropolyether (PFPE) and NOA63 as the mold resin and second replica mold material, respectively, play an important role in fabricating the structure. The structure is found to increase transmittance up to 82% at 540 nm and contact angle up to 150°, representing superhydrophobicity even without the aid of a fluorinated self‐assembled monolayer (SAM) coating. The resulting solid‐state dye‐sensitized solar cells (ssDSSCs) with moth‐eye structures show enhancement of efficiency to 7.3% at 100 mW cm^?2, which is among the highest values reported to date for N719 dye‐based ssDSSCs. This nature‐inspired nanopatterning process could be used for improving light harvesting in any type of photovoltaic cell, and it produces superhydrophobic surfaces, which in turn lead to self‐cleaning for long‐term stability.     

Surface‐Plasmon Assisted Energy Conversion in Dye‐Sensitized Solar Cells

In this study, the effect of plasmonic core‐shell structures, consisting of dielectric cores and metallic nanoshells, on energy conversion in dye‐sensitized solar cells (DSSCs) is investigated. The structure of the core‐shell particles is controlled to couple with visible light so that the visible component of the solar spectrum is amplified near the core‐shell particles. In core‐shell particle – TiO₂ nanoparticle films, the local field intensity and light pathways are increased due to the surface plasmons and light scattering. This, in turn, enlarges the optical cross‐section of dye sensitizers coated onto the mixed films. When 22 vol% of core‐shell particles are added to a 5 μm thick TiO₂ film, the energy conversion efficiency of DSSCs increases from 2.7% to 4.0%, in spite of a more than 20% decrease in the amount of dyes adsorbed on the composite films. The correlation between core‐shell particle content and energy conversion efficiency in DSSCs is explained by the balance among near‐field effects, light scattering efficiency, and surface area in the composite films.