Higher Incident Photon-to-current Conversion Efficiency Research Articles

Superior incident photon-to-current conversion efficiency of Mo-doped activated carbon supported CdS-sensitized solar cells.

In this study, the performance of activated carbon (AC) produced from defatted black cumin (Nigella sativa L.) by chemical activation with zinc chloride (ZnCl2) activator in photovoltaic application is evaluated. It is of great importance to increase the photovoltaic efficiency of cadmium sulfide (CdS)-based solar cells, which are widely used in photovoltaic applications, with AC support. The main purpose of the study is to determine how the incident photon-to-current conversion efficiency (IPCE) of undoped and Mo-doped AC supported CdS semiconductor materials changes in the presence of AC support material and to interpret the observed effect in the light of literature. For these reasons, in the study, AC supported CdS (CdS/AC) (5%, 10%, and 15% by weight) and Mo-doped CdS/AC semiconductor materials with different molybdenum (Mo) concentrations (0.33%, 1%, 3%) are produced by chemical precipitation method. Produced CdS/AC and Mo-doped CdS/AC semiconductor materials are characterized by IPCE, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) measurements. Based on the result values, the optimum CdS concentration with the highest IPCE (%) value is determined as 10% (for CdS/AC). As a result of the experimental measurements, the optimum Mo concentration with the maximum IPCE (%) value is found as 1% (for Mo-doped CdS/AC). In particular, it is clear that an appreciable increase (from 4.70 to 39.00%) in IPCE (%) of 1% Mo-doped 10% CdS/AC semiconductor material is achieved when compared to pure CdS. Thus, the ability to increase the photovoltaic efficiency of CdS-based solar cells, which are widely used in photovoltaic applications, with AC support has been clearly demonstrated. This study presents a new strategy to increase the solar cell efficiency of semiconductor-based solar cell structures using biowaste-based AC supported CdS semiconductor materials.

MoSexOy‐Coated 1D TiO2 Nanotube Layers: Efficient Interface for Light‐Driven Applications

AbstractUltrathin molybdenum oxyselenide (MoSexOy) coatings are made first ever by atomic layer deposition (ALD) within anodic 1D TiO2 nanotube layers for photoelectrochemical and photocatalytic applications. The coating thickness is controlled through varying ALD cycles from 5 to 50 cycles (corresponding to ≈1–10 nm). In the ultraviolet region, the coatings have enhanced up to four times the incident photon‐to‐current conversion efficiency (IPCE), and the highest IPCE is recorded at 32% at (at λ = 365 nm). The coatings notably extend the photoresponse to the visible spectral region and remarkable improvement of photocurrent densities up to ≈40 times is registered at λ = 470 nm. As a result, the MoSexOy‐coated‐TiO2 nanotube layers have shown to be an effective photocatalyst for methylene blue degradation, and the optimal performance is credited to a coating thickness between 2 and 5 nm (feasible only by ALD). The enhancement in photoactivities of the presented heterojunction is mainly associated with the passivation effect of MoSexOy on the TiO2 nanotube walls and the suitability of bandgap position between MoSexOy and TiO2 interface for an efficient charge transfer. In addition, MoSexOy possesses a narrow bandgap, which favors the photoactivity in the visible spectral region.

A Near‐Infrared cis‐Configured Squaraine Co‐Sensitizer for High‐Efficiency Dye‐Sensitized Solar Cells

AbstractA cis‐configured squaraine dye (HSQ1), synthesized by incorporation of a strongly electron‐withdrawing dicyanovinyl group into the central squaric acid moiety, is employed in dye‐sensitized solar cells (DSCs). In solution, HSQ1 displays an intense absorption in the near‐infrared region with a maximum at 686 nm and when the dye is adsorbed on a TiO2 surface, the absorption spectrum broadens in both the blue and the near‐infrared regions, which is favorable for efficient light harvesting over a broad wavelength range. A solar cell sensitized with HSQ1 shows a broader incident photon‐to‐current conversion efficiency (IPCE) spectrum (from 400 to 800 nm) and a higher IPCE in the long‐wavelength region (71% at 700 nm) than a cell sensitized with squaraine dye SQ1. Furthermore, a solar cell co‐sensitized with HSQ1 and N3 dye shows remarkably improved short‐circuit current density and open‐circuit voltage compared to those of a DSC based on N3 alone and fabricated under the same conditions. The energy‐conversion efficiency of the co‐sensitized DSC is 8.14%, which is the highest reported efficiency for a squaraine dye–based co‐sensitized DSC without using Al2O3 layer.

Light management in dye-sensitized solar cell

Dye-sensitized solar cell (DSSC) is composed of a nanocrystalline TiO2 film whose surface is covered with dye molecules, an iodide/tri-iodide electrolyte and a platinum counter electrode. Charge generation occurs when dye absorbs photon energy, which is separated by injection of photo-excited electrons into the conduction band of TiO2. The photo-injected electrons are transported through TiO2 network and collected at transparent conducting electrode. The oxidized dyes are regenerated by oxidation of iodide. Light-to-electricity conversion efficiency depends on photocurrent density, open-circuit voltage and fill factor. Photocurrent density is related to the incident photon-to-current conversion efficiency (IPCE) that is a collective measure of light harvesting, charge separation and charge collection efficiency. Since the higher IPCE, the higher photocurrent density becomes, light management in DSSC is one of most important issues. In this paper, effective methods to improve IPCE are described including size-dependent light scattering effect, bi-functionality design in material synthesis and panchromatic approach such as selective position of different dyes in a mesoporous TiO2 film.

Thin film TiO 2 photoanodes for water photolysis prepared by dc magnetron sputtering

The TiO 2 thin film photoanodes for hydrogen generation by water photolysis have been prepared by dc reactive magnetron sputtering. Optical monitoring of the plasma emission with the feedback signal I/ I 0 controlling the reactive gas admission and reflecting the target oxidation state has been used. X-ray diffraction GID and AFM studies have revealed the systematic evolution of the microstructure with I/ I 0, from that of well-crystallized mixture of anatase and rutile at the lowest I/ I 0 (oxidized target) to that of amorphous state with finely dispersed rutile grains at the highest I/ I 0 (metallic target). It has been demonstrated that the microstructure of TiO 2 affects to a large extent the optical and photoelectrochemical properties of the photoanodes. Optical band gap E opt and the photocurrent response have been found to increase systematically with a decreasing feedback signal I/ I 0. The best efficiency, i.e. the highest IPCE (incident photon-to-current conversion efficiency) has been obtained for the TiO 2 photoanodes sputtered at I/ I 0 = 0.09 from the oxidized target.