Recent Developments in Dye-Sensitized Solar Cells

The current state of the art in internal additive materials and quantum dots for improving efficiency and stability against humidity in perovskite solar cells

The remarkable optoelectronic capabilities of perovskite structures enable the achievement of astonishingly high-power conversion efficiencies on the laboratory scale. However, a critical bottleneck of perovskite solar cells is their sensitivity to the surrounding humid environment affecting drastically their long-term stability. Internal additive materials together with surface passivation, polymer-mixed perovskite, and quantum dots, have been investigated as possible strategies to enhance device stability even in unfavorable conditions. Quantum dots (QDs) in perovskite solar cells enable power conversion efficiencies to approach 20%, making such solar cells competitive to silicon-based ones. This mini-review summarized the role of such QDs in the perovskite layer, hole-transporting layer (HTL), and electron-transporting layer (ETL), demonstrating the continuous improvement of device efficiencies.

The Golden Fig: A Plasmonic Effect Study of Organic-Based Solar Cells

An optimization work on dye-sensitized solar cells (DSSCs) based on both artificial and natural dyes was carried out by a fine synthesis work embedding gold nanoparticles in a TiO₂ semiconductor and perfecting the TiO₂ particle sizes of the scattering layer. Noble metal nanostructures are known for the surface plasmon resonance peculiarity that reveals unique properties and has been implemented in several fields such as sensing, photocatalysis, optical antennas and PV devices. By embedding gold nanoparticles in the mesoporous TiO₂ layer and adding a scattering layer, we were able to boost the power conversion efficiency (PCE) to 10.8%, using an organic ruthenium complex. The same implementation was carried out using a natural dye, betalains, extracted from Sicilian prickly pear. In this case, the conversion efficiency doubled from 1 to 2% (measured at 1 SUN illumination, 100 mW/cm² under solar simulation irradiation). Moreover, we obtained (measured at 0.1 SUN, 10 mW/cm² under blue light LED irradiation) a record efficiency of 15% with the betalain-based dye, paving the way for indoor applications in organic natural devices. Finally, an attempt to scale up the system is shown, and a betalain-based- dye-sensitized solar module (DSSM), with an active area of 43.2 cm² and a PCE of 1.02%, was fabricated for the first time.

Semiconductors as Effective Electrodes for Dye Sensitized Solar Cell Applications

As proficient photovoltaic devices, dye-sensitized solar cells (DSSCs) have received considerable consideration in recent years. In order to accomplish advanced solar-to-electricity efficiency and increase long-term functioning stability, improvements in the configuration structure of DSSCs are essential, as is an understanding of their elementary principles. This work discusses the application of different semiconductor constituents designed for effective DSSCs. The main parameters crucial to fabrication of DSSC electrodes in nano-porous semiconductor structures are high surface area and large pore size. Different inorganic semiconductor materials are used to load sensitizer dyes, which absorb a lot of light and induce high photocurrent for efficient DSSCs. The first section of the review covers energy sources, photovoltaics, and the benefits of solar cells in daily life, while the second part includes the various types of semiconductors applied in DSSC applications. The final section provides a brief review of future perspectives for DSSCs and a survey of semiconductor materials proposed for solar cell applications.

Density functional theory study on the donating strength of donor systems in dye-sensitized solar cells

Donating strength of typically used donors in dye-sensitized solar cells.

Ru(II) porphyrins as sensitizers for DSSCs: Axial vs. peripheral carboxylate anchoring group

In this study, two porphyrin chromophores metallated with ruthenium, RuTBP and RuTBPPy, were prepared and studied as sensitizers in dye-sensitized solar cells (DSSCs). The difference between the two dyes is the position (axial vs. peripheral) of the carboxylic anchoring group. This work examines the impact of this variation towards the optical, electrochemical and photovoltaic performance of DSSCs. The thorough photophysical and photovoltaic measurements indicated that the peripherally substituted sensitizer (RuTBP) presented higher photovoltaic performance compared to RuTBPPy. More specifically, DSSCs sensitized with RuTBP and RuTBPPy displayed an overall power conversion efficiency (PCE) of 5.12% and 4.08%, respectively. The higher PCE value of the DSSC sensitized with RuTBP is mainly attributed to the enhancement of [Formula: see text] and FF values. These factors were enhanced due to the efficient dye regeneration process, the suppression of back-charge recombination reactions and the longer electron lifetimes as evidenced from the electrochemical impedance spectra.

Boron-doped graphene quantum dots: an efficient photoanode for a dye sensitized solar cell

A cost effective boron doped graphene quantum dot from boron carbide graphene by microwave reactor assisted process that can tune the properties of metal oxides for DSSC application is proposed by D. K. Pattanayak, S. Kundu, T. N. Narayanan and co-workers.

Enhanced photoresponse of a high-performance self-powered UV photodetector based on ZnO nanorods and a novel electrolyte by the piezo-phototronic effect

A flexible self-powered ultraviolet (UV) photodetector based on ZnO nanorods (NRs) and a novel iodine-free quasi solid-state electrolyte was fabricated. The obtained device has a fast and high response to UV light illumination at zero bias and also shows long-term stability. The responsivity is 50.5 mA W⁻¹ and the response time is less than 0.2 s. Strain-induced piezo-phototronic potential within wurtzite-structured ZnO can optimize the performance of corresponding optoelectronic devices since it could effectively tune the charge carriers' separation and transport. The photoresponse performances of the photodetector under different upward angles (tensile strain) and downward angles (compressive strain) at 0 V bias were studied in detail. A 163% change of responsivity was obtained when the downward angle reached 60°. The enhancement could be interpreted by the piezo-phototronic effect. The piezoelectric potential (piezopotential) at the ZnO NRs/electrolyte interface can expand the built-in field, and as a result, it is easier for charge carriers to separate and transport.

A flexible UV detector exhibits high performance. The photoresponse of the device under different upward angles (tensile strain) and downward angles (compressive strain) were studied. A 163% change in responsivity was obtained when the downward angle reached 60°.

Versatile ruthenium(II) dye towards blue-light emitter and dye-sensitizer for solar cells

A versatile Ru(II) complex bearing an anthracene moiety was synthesized in our search for suitable compounds towards efficient molecular devices. The new engineered dye, cis‑[Ru(dcbH₂)(NCS)₂(mbpy‑anth)] (dcbH₂=2,2'‑bipyridyl‑4,4'‑dicarboxylic acid, mbpy‑anth=4‑[N‑(2‑anthryl)carbamoyl]‑4'‑methyl‑2,2'‑bipyridine), exhibits a blueish emission in a vibronically structured spectrum ascribed to the fluorescence of a ¹LC_Anth (ligand centered) excited state in the anthracene and has a potential to be exploited in the fields of smart lighting and displays. This complex was also employed in dye-sensitized solar cells with fairly efficient solar energy conversion with the use of self-assembled TiO₂ compact layers beneath the TiO₂ mesoporous film to prevent meso‑TiO₂/dye back reactions. Further photoelectrochemical investigations through incident photon-to-current efficiency and electrochemical impedance spectra showed that the all-nano-TiO₂ compact layer acts as contact layers that increase the electron harvesting in the external circuit, enhancing efficiencies up to 50%.

Polymeric Materials for Conversion of Electromagnetic Waves from the Sun to Electric Power

Solar photoelectric energy converted into electricity requires large surface areas with incident light and flexible materials to capture these light emissions. Currently, sunlight rays are converted to electrical energy using silicon polymeric material with efficiency up to 22%. The majority of the energy is lost during conversion due to an energy gap between sunlight photons and polymer energy transformation. This energy conversion also depends on the morphology of present polymeric materials. Therefore, it is very important to construct mechanisms of highest energy occupied molecular orbitals (HOMO)s and the lowest energy unoccupied molecular orbitals (LUMO)s to increase the efficiency of conversion. The organic and inorganic solar cells used as dyes can absorb more photons from sunlight and the energy gap will be less for better conversion of energy to electricity than the conventional solar cells. This paper provides an up-to-date review on the performance, characterization, and reliability of different composite polymeric materials for energy conversion. Specific attention has been given to organic solar cells because of their several advantages over others, such as their low-energy payback time, conversion efficiency and greenhouse emissions. Finally, this paper provides the recent progress on the application of both organic and inorganic solar cells for electric power generations together with several challenges that are currently faced.

Multimolecular assemblies on high surface area metal oxides and their role in interfacial energy and electron transfer

High surface area metal oxides offer a unique substrate for the assembly of multiple molecular components at an interface.

A 3D architecture composite of porous vanadium nitride nanoribbons and reduced graphene oxide as a high-efficiency counter electrode for dye-sensitized solar cells

A three-dimensional (3D) porous architecture combining porous vanadium nitride nanoribbons with reduced graphene oxide was prepared through a hydrothermal process and subsequent thermal annealing in an ammonia/argon mixed atmosphere. Then, the obtained 3D porous vanadium nitride nanoribbon/reduced graphene oxide (PVNN/RGO) composite was explored as the counter electrode of dye-sensitized solar cells (DSCs). As evidenced by the electrochemical measurements, the 3D PVNN/RGO composite demonstrates excellent electrocatalytic performance, which is comparable to that of Pt. This can be attributed to the fact that the 3D architecture composite of porous vanadium nitride and reduced graphene oxide can simultaneously provide a favorable electrolyte diffusion channel, a fast electron-transport network, and an abundance of efficient electrocatalytic active sites. By employing such PVNN/RGO composite as the counter electrode, the fabricated DSC can achieve a conversion efficiency of 7.43%, which is comparable to that of the conventional Pt counter electrode (7.74%). Therefore, the 3D PVNN/RGO composite is a promising low-cost alternative to the expensive Pt as a counter electrode in DSCs.

3D PVNN/RGO composite electrode with hierarchical porosity exhibits superior photovoltaic performance competing with that of the conventional Pt electrode.

X-Ray diffraction and resonance shear measurement of nano-confined ionic liquids

The X-ray diffraction and resonance shear measurement (RSM) demonstrated the relation between the structure and lubrication properties of ionic liquid ([C₄mim][NTf₂], [C₄mim][BF₄]) films of nanometer thickness confined between silica surfaces.

Determining the Conduction Band-Edge Potential of Solar-Cell-Relevant Nb2O5 Fabricated by Atomic Layer Deposition

Often key to boosting photovoltages in photoelectrochemical and related solar-energy-conversion devices is the preferential slowing of rates of charge recombination-especially recombination at semiconductor/solution, semiconductor/polymer, or semiconductor/perovskite interfaces. In devices featuring TiO₂ as the semiconducting component, a common approach to slowing recombination is to install an ultrathin metal oxide barrier layer or trap-passivating layer atop the semiconductor, with the needed layer often being formed via atomic layer deposition (ALD). A particularly promising barrier layer material is Nb₂O₅. Its conduction-band-edge potential E_CB is low enough that charge injection from an adsorbed molecular, polymeric, or solid-state light absorber and into the semiconductor can still occur, but high enough that charge recombination is inhibited. While a few measurements of E_CB have been reported for conventionally synthesized, bulk Nb₂O₅, none have been described for ALD-fabricated versions. Here, we specifically determine the conduction-band-edge energy of ALD-fabricated Nb₂O₅ relative to that of TiO₂. We find that, while the value for ALD-Nb₂O₅ is indeed higher than that for TiO₂, the difference is less than anticipated based on measurements of conventionally synthesized Nb₂O₅ and is dependent on the thermal history of the material. The implications of the findings for optimization of competing interfacial rate processes, and therefore photovoltages, are briefly discussed.

Synthesis of a dibenzo-BODIPY-incorporating phenothiazine dye as a panchromatic sensitizer for dye-sensitized solar cells

The introduction of dibenzo-BODIPY into a phenothiazine dye led to the production of a panchromatic sensitizer for dye-sensitized solar cells, a cell with the dye showing a PCE (η) value of 7.69%.

Broadband and Low-Loss Plasmonic Light Trapping in Dye-Sensitized Solar Cells Using Micrometer-Scale Rodlike and Spherical Core-Shell Plasmonic Particles

Dielectric scattering particles have widely been used as embedded scattering elements in dye-sensitized solar cells (DSCs) to improve the optical absorption of the device. Here we systematically study rodlike and spherical core-shell silica@Ag particles as more effective alternatives to the dielectric scattering particles. The wavelength-scale silica@Ag particles with sufficiently thin Ag shell support hybrid plasmonic-photonic resonance modes that have low parasitic absorption losses and a broadband optical response. Both of these features lead to their successful deployment in light trapping in high-efficiency DSCs. Optimized rodlike silica@Ag@silica particles improve the power conversion efficiency of a DSC from 6.33 to 8.91%. The dimension, surface morphology, and concentration of these particles are optimized to achieve maximal efficiency enhancement. The rodlike silica particles are prepared in a simple one-pot synthesis process and then are coated with Ag in a liquid-phase deposition process by reducing an Ag salt. The aspect ratio of silica rods is tuned by adjusting the temperature and duration of the growth process, whereas the morphology of Ag shell is tailored by controlling the reduction rate of Ag salt, where slower reduction in a polyol process gives a smoother Ag shell. Using optical calculations, the superior performance of the plasmonic core-shell particles is related to the large number of hybrid photonic-plasmonic resonance modes that they support.

Multifunctional Iodide-Free Polymeric Ionic Liquid for Quasi-Solid-State Dye-Sensitized Solar Cells with a High Open-Circuit Voltage

A polymeric ionic liquid, poly(oxyethylene)-imide-imidazolium selenocyanate (POEI-IS), was newly synthesized and used for a multifunctional gel electrolyte in a quasi-solid-state dye-sensitized solar cell (QSS-DSSC). POEI-IS has several functions: (a) acts as a gelling agent for the electrolyte of the DSSC, (b) possesses a redox mediator of SeCN(-), which is aimed to form a SeCN(-)/(SeCN)3(-) redox couple with a more positive redox potential than that of traditional I(-)/I3(-), (c) chelates the potassium cations through the lone pair electrons of the oxygen atoms of its poly(oxyethylene)-imide-imidazolium (POEI-I) segments, and (d) obstructs the recombination of photoinjected electrons with (SeCN)3(-) ions in the electrolyte through its POEI-I segments. Thus, the POEI-IS renders a high open-circuit voltage (VOC) to the QSS-DSSC due to its functions of b-d and prolongs the stability of the cell due to its function of a. The QSS-DSSC with the gel electrolyte containing 30 wt % of the POEI-IS in liquid selenocyanate electrolyte exhibited a high VOC of 825.50 ± 3.51 mV and a high power conversion efficiency (η) of 8.18 ± 0.02%. The QSS-DSSC with 30 wt % POEI-IS retained up to 95% of its initial η after an at-rest stability test with the period of more than 1,000 h.

Progress on nanoparticle-based carbon nanotube complex: fabrication and potential application

Carbon nanotubes (CNTs) are considered as one of the most intensively explored nanostructured materials and have been widely used as a platform material for metal and semiconductor nanoparticles (NPs) due to their large and chemically active surface area. Several approaches have been described in the literature to immobilize NPs on the surface of CNTs. This report reviews the recent developments in this area by exploring the various techniques where nanotubes can be functionalized with NPs to improve the optical, mechanical, thermal, medical, electrical, and magnetic applications of CNTs.

A novel triphenylamine-based dye sensitizer supported on titania nanoparticles and the effect of titania fabrication on its optical properties

A new synthesised triphenylamine-based dye having a branched structure with one OH-ending branch able to interact with the surface hydroxyl moieties of mesoporous TiO

Bilayer structured supramolecular light harvesting arrays based on zinc porphyrin coordination polymers for enhanced photocurrent generation in dye sensitized solar cells

Coordination polymers based on an acylhydrazone zinc porphyrin were synthesized and applied in dye sensitized solar cells for enhanced photocurrent generation.

Surface passivation of titanium dioxide via an electropolymerization method to improve the performance of dye-sensitized solar cells

We introduce an electrochemical method for insulating and passivation open areas of a nanoporous TiO₂ in dye-sensitized solar cells, which can effectively decrease the recombination rate of electrons.

High performance dye-sensitized solar cell from a cocktail solution of a ruthenium dye and metal free organic dye

A Ru-based dye K-60 and a metal free D–A organic dye Y1 have been employed for the fabrication of a mixed dye sensitized solar cell (MDSSCs) system.

3D bicontinuous SnO2/TiO2 core/shell structures for highly efficient organic dye-sensitized solar cell electrodes

SnO₂/TiO₂ core/shell hybrid structures with a 3D bicontinuous morphology were demonstrated as an electrode for dye-sensitized solar cells.

Organic Charge Carriers for Perovskite Solar Cells

The photovoltaic field is currently experiencing the "perovskite revolution". These materials have been known for decades, but only recently have they been applied in solid-state solar cells to obtain outstanding power conversion efficiencies. Given that the variety of perovskites used so far is limited, a lot of attention has been devoted to the development of suitable organic charge-transport materials to improve device performance. In this article, we will focus on the most promising materials able to transport electrons or holes from a structural point of view. Thereby, we focus on organic materials owing to their ease of preparation and manipulation, and this is nicely combined with the potential tuning of their properties through chemical synthesis.

Electrodes/electrolyte interfaces in the presence of a surface-modified photopolymer electrolyte: application in dye-sensitized solar cells

Since hundreds of studies on photoanodes and cathodes show that the electrode/electrolyte interfaces represent a key aspect at the base of dye-sensitized solar cell (DSSC) performances, it is reported here that these interfaces can be managed by a smart design of the spatial composition of quasi-solid electrolytes. By means of a cheap, rapid, and green process of photoinduced polymerization, composition-tailored polymer electrolyte membranes (PEMs) with siloxane-enriched surfaces are prepared, and their properties are thoroughly described. When assembled in DSSCs, the interfacial action promoted by the composition-tailored PEMs enhances the photocurrent and fill factor values, thus increasing the global photovoltaic conversion efficiency with respect to the non-modified PEMs. Moreover, the presence of the siloxane-chain-enriched surface increases the hydrophobicity and reduces the water vapor permeation into the device, thus enhancing the cell's durability.

Structural stability and polarisation of ionic liquid films on silica surfaces

Using molecular dynamics simulations, we studied the structure of [BMIM][NTF2] and [BMIM][BF4] liquid films on hydroxylated silica surfaces. The results pointed out that the main features of the solid–liquid interface were present on both crystalline and amorphous silica, and how these determine their electrostatic properties.

Functional quasi-solid-state electrolytes for dye sensitized solar cells prepared by amine alkylation reactions

Novel quasi-solid state electrolytes for dye-sensitized solar cells (QSS-DSCs) are prepared by the amine alkylation reaction.