Nanostructured semiconductor materials for dye-sensitized solar cells

Since O'Regan and Grätzel's first report in 1991, dye-sensitized solar cells (DSSCs) appeared immediately as a promising low-cost photovoltaic technology. In fact, though being far less efficient than conventional silicon-based photovoltaics (being the maximum, lab scale prototype reported efficiency around 13%), the simple design of the device and the absence of the strict and expensive manufacturing processes needed for conventional photovoltaics make them attractive in small-power applications especially in low-light conditions, where they outperform their silicon counterparts. Nanomaterials are at the very heart of DSSC, as the success of its design is due to the use of nanostructures at both the anode and the cathode. In this review, we present the state of the art for both n-type and p-type semiconductors used in the photoelectrodes of DSSCs, showing the evolution of the materials during the 25 years of history of this kind of devices. In the case of p-type semiconductors, also some other energy conversion applications are touched upon. © 2017 Carmen Cavallo et al

Controlling the Microstructure and Properties of Titanium Dioxide for Efficient Solar Cells

In this chapter, we review the controlling of the microstructures, the properties, and the different methods to obtain titanium dioxide and the application of these materials on solar cells. We will concentrate on the application of efficient solar cells including dye-sensitized solar cells (DSSCs). In the first section, we provide a background on energy, including its sources—photovoltaics and titanium dioxide—and the advantages of their application in solar cells. The second section outlines the different methods to obtain TiO2 nanoparticles. The shapes of titanium dioxide are explored in the third section. In the fourth section, we discuss the use and effect of the titanium dioxide in the efficient dye-sensitized solar cells, and the last section is a summary of the current state of the art and perspectives of titanium dioxide for efficient solar cells

How mobile are dye adsorbates and acetonitrile molecules on the surface of TiO2 nanoparticles? A quasi-elastic neutron scattering study

Motions of molecules adsorbed to surfaces may control the rate of charge transport within monolayers in systems such as dye sensitized solar cells. We used quasi-elastic neutron scattering (QENS) to evaluate the possible dynamics of two small dye moieties, isonicotinic acid (INA) and bis-isonicotinic acid (BINA), attached to TiO2 nanoparticles via carboxylate groups. The scattering data indicate that moieties are immobile and do not rotate around the anchoring groups on timescales between around 10 ps and a few ns (corresponding to the instrumental range). This gives an upper limit for the rate at which conformational fluctuations can assist charge transport between anchored molecules. Our observations suggest that if the conformation of larger dye molecules varies with time, it does so on longer timescales and/or in parts of the molecule which are not directly connected to the anchoring group. The QENS measurements also indicate that several layers of acetonitrile solvent molecules are immobilized at the interface with the TiO2 on the measurement time scale, in reasonable agreement with recent classical molecular dynamics results

Coupling gold nanoparticles to Dye-Sensitized Solar Cells for an increased efficiency

New approaches for coupling Au NPs to the photoanode of dye sensitized solar cells (DSSCs) were proposed herein, aiming to improve the typical energy conversion efficiency of these cells. For this purpose, colloidal Au NPs with different particles sizes, ∼5 nm and ∼22 nm, were chemically synthesized and attached (i) directly to titanium dioxide (TiO2) or (ii) to TiO2 surface modified with siliceous shells enriched in dithiocarbamate moieties (SiO2/SiDTC). Photoanodes composed by films of TiO2 anatase, TiO2@Au NPs (∼5 nm and ∼22 nm), or TiO2 functionalized with SiO2/SiDTC, loaded with colloidal Au NPs, were made. DSSCs were set-up in a typical sandwich configuration, using the photoanode, a Pt counter electrode, and an iodide electrolyte solution (I−/I3−). In general, a relevant contribution in the plasmonic DSSC performance was evidenced by using Au NPs of ∼22 nm loaded in different amounts 23.9 wt%, 31.0 wt% and 44.0 wt%. Photoanodes composed by 23.9% of Au yielded an increment of 14.40% in photocurrent and of 11.21% in the overall power conversion efficiency (PCE), when compared to the conventional one. In turn, the new strategy used in the chemical modification of the conventional photoanodes with dithiocarbamate groups showed also a significant improvement of the DSSC parameters.publishe

Research and Development Aspects on Chemical Preparation Techniques of Photoanodes for Dye Sensitized Solar Cells

The importance of dye sensitized solar cells (DSSCs) as a low-cost and environmentally friendly photovoltaic (PV) technology has prompted many researchers to improve its efficiency and durability. The realization of these goals is impossible without taking into account the importance of the materials in DSSCs, so the focus on the preparation/deposition methods is essential. These methods can be either chemical or physical. In this study, the chemical applied methods that utilize chemical reaction to synthesize and deposit the materials are covered and categorized according to their gas phase and liquid phase precursors. Film processing techniques that can be used to enhance the materials' properties postpreparation are also included for further evaluation in this study. However, there is a variety of consideration, and certain criteria must be taken into account when selecting a specific deposition method, due to the fact that the fabrication conditions vary and are unoptimized

Solar Cells

The second book of the four-volume edition of "Solar cells" is devoted to dye-sensitized solar cells (DSSCs), which are considered to be extremely promising because they are made of low-cost materials with simple inexpensive manufacturing procedures and can be engineered into flexible sheets. DSSCs are emerged as a truly new class of energy conversion devices, which are representatives of the third generation solar technology. Mechanism of conversion of solar energy into electricity in these devices is quite peculiar. The achieved energy conversion efficiency in DSSCs is low, however, it has improved quickly in the last years. It is believed that DSSCs are still at the start of their development stage and will take a worthy place in the large-scale production for the future

Microwave Plasmas as a Processing Tool for Tailoring the Surface Properties of Ceramic Coatings

This chapter reviews the use of low pressure microwave plasmas as a processing technology for both sintering and controlling the surface chemistry of porous ceramic coatings. A particular advantage of microwave processing is its ability to penetrate the surface of the workpiece; enabling rapid volumetric heating and thus reducing the need for external heat sources. The microwave plasma treatments have the ability to sinter materials in minutes rather than the hours taken using conventional furnace processing. This study provides examples of the use of these plasmas to sinter both nickel and titanium nanoparticles. These are used in the fabrication of electrodes for use in dye sensitized solar cells. Further applications of the microwave plasma treatments investigated is for their use in heat treatment to control crystalline phase transitions, as well as a rapid technique to oxidize metal surfaces

Ion Beam Techniques and Applications

A wide variety of ion beam techniques are being used in several versatile applications ranging from environmental science, nuclear physics, microdevice fabrication to materials science. In addition, new applications of ion beam techniques across a broad range of disciplines and fields are also being discovered frequently. In this book, the latest research and development on progress in ion beam techniques has been compiled and an overview of ion beam irradiation-induced applications in nanomaterial-focused ion beam applications, ion beam analysis techniques, as well as ion implantation application in cells is provided. Moreover, simulations of ion beam-induced damage to structural materials of nuclear fusion reactors are also presented in this book

Controllable Core Size of Au@TiO2 through Al(NO3)3 Addition and Its Effects on DSSC Performance

It is known that plasmonic nanoparticles in dye-sensitized solar cells (DSSC) could enhance efficiency through improvement in light absorbance and electron dynamics. Herein we investigated various sizes of AuNP through spontaneous Al(NO3 )3 addition. Core-Shell Au@TiO2 was prepared with various Al(NO3 )3 concentrations of 0.25 mM, 0.5 mM, 0.75 mM and 1 mM. The Au@TiO2 volume fraction of 1% was further added to TiO2 photoanode. Based on the particle size analyzer (PSA) characteristics, the synthesized AuNP’s size was within a range of 34.62 nm – 139.5 nm. The highest efficiency of DSSC was obtained for the sample with the largest AuNP ’s diameter, i.e., 0.0313%, which is about three times higher than pristine DSSC. The increase in efficiency was in accord with Metallic Nanoparticle Boundary Element Method (MNPBEM) simulation, UV-vis spectroscopy, and Incident Photon to Current Conversion Efficiency (IPCE) analysis largest Au core diameter contributes to the strong absorbance and hence the short circuit curren