Butyronitrile-based electrolyte for dye-sensitized solar cells

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW·cm(-2) incident solar radiation intensity, respectively. We reached >95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW·cm(-2) light-soaking exposure at 60 °C.     

New architectures for dye-sensitized solar cells

Modern dye-sensitized solar cell (DSSC) technology was built upon nanoparticle wide bandgap semiconductor photoanodes. While versatile and robust, the sintered nanoparticle architecture exhibits exceedingly slow electron transport that ultimately restricts the diversity of feasible redox mediators. The small collection of suitable mediators limits both our understanding of an intriguing heterogeneous system and the performance of these promising devices. Recently, a number of pseudo-1D photoanodes that exhibit accelerated charge transport and greater materials flexibility were fabricated. The potential of these alternative photoanode architectures for advancing, both directly and indirectly, the performance of DSSCs is explored.     

Liquid electrolytes for dye-sensitized solar cells

The present review offers a survey of liquid electrolytes used in dye-sensitized solar cells from the beginning of photoelectrochemical cell research. It handles both the solvents employed, and the prerequisites identified for an ideal liquid solvent, as well as the various effects of electrolyte solutes in terms of redox systems and additives. The conclusions of the present review call for more detailed molecular insight into the electrolyte-electrode interface reactions and structures.     

Optimizing dyes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have emerged as an important cheap photovoltaic technology. Charge separation is initiated at the dye, bound at the interface of an inorganic semiconductor and a hole-transport material. Careful design of the dye can minimize loss mechanisms and improve light harvesting. Mass application of DSSCs is currently limited by manufacturing complexity and long-term stability associated with the liquid redox electrolyte used in the most-efficient cells. In this Minireview, dye design is discussed in the context of novel alternatives to the standard liquid electrolyte. Rapid progress is being made in improving the efficiencies of such solid and quasi-solid DSSCs which promises cheap, efficient, and robust photovoltaic systems.     

Arylamine-based dyes for p-type dye-sensitized solar cells

New arylamine-based sensitizers for p-type dye-sensitized solar cells (DSSCs) have been synthesized and used for p-type DSSCs. The best conversion efficiency reaches ～0.1%. Sensitizers with two anchoring carboxylic acids lead to higher open-circuit voltages, short-circuit currents, and energy conversion efficiencies.     

Phenothiazinyl rhodanylidene merocyanines for dye-sensitized solar cells

Phenothiazinyl rhodanylidene acetic acid merocyanine dyes with variable substitution pattern on the peripheral benzene ring were synthesized in good to excellent yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and rhodanine-N-acetic acid. The electronic properties were investigated by cyclic voltammetry, absorption, and fluorescence spectroscopy. Electron releasing substitution leads to an appreciable lowering of the oxidation potential, bathochromic shift of the absorption band, and minimization of the emission quantum yield. Not least as a consequence of these properties, the compounds are interesting for use as chromophores in dye-sensitized solar cells (DSSC). DSSCs were constructed and successfully tested by determining the characteristic parameters such as incident-photon-to-electron conversion efficiency (IPCE), fill factor (FF), and overall efficiency.     

Ionic liquid electrolytes for dye-sensitized solar cells

The potential of room-temperature molten salts (ionic liquids) as solvents for electrolytes for dye-sensitized solar cells has been investigated during the last decade. The non-volatility, good solvent properties and high electrochemical stability of ionic liquids make them attractive solvents in contrast to volatile organic solvents. Despite this, the relatively high viscosity of ionic liquids leads to mass-transport limitations. Here we review recent developments in the application of different ionic liquids as solvents or components of liquid and quasi-solid electrolytes for dye-sensitized solar cells.     

New difluorenylaminocoumarin photosensitizers for dye-sensitized solar cells

Research on Chemical Intermediates - Three difluorenylaminocoumarin sensitizers with different π-bridges bearing thiophene ring and cyanoacrylic acid acceptor were synthesized and their...     

Dihydrophenazine-based double-anchoring dye for dye-sensitized solar cells

A novel dihydrophenazine-based organic di-anchoring dye DK-11 was synthesized by utilizing a simple synthetic protocol. The dye was characterized by optical and electrochemical studies and used as a sensitizer for dye-sensitized solar cell. The proposed butterfly structure was supported by IR experiments which ensured the binding of both carboxylic acid units on the semiconductor surface. Using the dye DK-11 , the device generated an efficiency of 5.07% with J_SC, V_OC, and FF values of 10.65 mA/cm², 0.67 V, and 0.71, respectively.     

Thiophene-fused coplanar sensitizer for dye-sensitized solar cells

We have designed and synthesized a novel ladder-type heteroacene dye consisting uniquely of thiophene segments as a photosensitizer for the dye-sensitized solar cells (DSSCs). The onset of the IPCE spectrum for the dye not only reaches up to 700 nm with a high IPCE (>60%) but also a solar energy-to-electricity conversion efficiency of 2.31% is achieved. Even though the efficiency is slightly lower than those of other dyes reported previously, this work opens up a new strategy to design heteroaromatic fused photosensitizers for DSSCs.     

Charge separation versus recombination in dye-sensitized nanocrystalline solar cells: the minimization of kinetic redundancy

In this paper we focus upon the electron injection dynamics in complete dye-sensitized nanocrystalline metal oxide solar cells (DSSCs). Electron injection dynamics are studied by transient absorption and emission studies of DSSCs and correlated with device photovoltaic performance and charge recombination dynamics. We find that the electron injection dynamics are dependent upon the composition of the redox electrolyte employed in the device. In a device with an electrolyte composition yielding optimum photovoltaic device efficiency, electron injection kinetics exhibit a half time of 150 ps. This half time is 20 times slower than that for control dye-sensitized films covered in inert organic liquids. This retardation is shown to result from the influence of the electrolyte upon the conduction band energetics of the TiO2 electrode. We conclude that optimum DSSC device performance is obtained when the charge separation kinetics are just fast enough to compete successfully with the dye excited-state decay. These conditions allow a high injection yield while minimizing interfacial charge recombination losses, thereby minimizing "kinetic redundancy" in the device. We show furthermore that the nonexponential nature of the injection dynamics can be simulated by a simple inhomogeneous disorder model and discuss the relevance of our findings to the optimization of both dye-sensitized and polymer based photovoltaic devices.     

Recent progress in interface modification for dye-sensitized solar cells

Interface modification on the TiO₂/dye/electrolyte interface of dye-sensitized solar cells (DSCs) is one of the most effective approaches to suppress the charge recombination, improve electron injection and transportation, and thus ameliorate the conversion efficiency and stability of DSCs. Conventional research focusing on the photoanodes interface modification before sensitization in dye-sensitized solar cells has been carried out and reviewed. However, recent studies showed that post-modification after sensitization of the TiO₂ electrode also plays a significant role on the TiO₂/dye/electrolyte interface. This post-modification using the immersing method could deprotonate dye molecules, prohibit the dye aggregation and retard the recombination reaction. As a result, it has great influence on the devices’ photovoltaic performance. This interface modification could also provide an approach to broaden the response of the solar spectrum by introducing an alternative assembling structure. An in-situ meaning of using a co-adsorbent is employed to modify the interface in the DSCs, which could retard the aggregation of the dye molecules and enhance the conversion efficiency. In addition, electrolyte additives can be used to modify the TiO₂/dye/electrolyte interface through some unique mechanisms. Based on the background of interface modification of photoanodes before sensitization, this review introduces various interface modifications after sensitization of dye-sensitized solar cells and their mechanisms.     

Recent advances in phenothiazine-based dyes for dye-sensitized solar cells

Dye-sensitized solar cells(DSSCs) have attracted significant attention as alternatives to conventional silicon-based solar cells owing to their low-cost production,facile fabrication,excellent stability and high power conversion efficiency(PCE).The dye molecule is one of the key components in DSSCs since it significant influence on the PCE,charge separation,light-harvesting,as well as the device stability.Among various dyes,easily tunable phenothiazine-based dyes hold a large proportion and achieve impressive photovoltaic performances.This class of dyes not only has superiorly non-planar butterfly structure but also possesses excellent electron donating ability and large π conjugated system.This review summarized recent developments in the phenothiazine dyes,including small molecule phenothiazine dyes,polymer phenothiazine dyes and phenothiazine dyes for co-sensitization,especially focused on the developments and design concepts of small molecule phenothiazine dyes,as well as the correlation between molecular structures and the photovoltaic performances.     

Highly-efficient metal-free organic dyes for dye-sensitized solar cells

A solar-to-electric conversion efficiency of 6.1% is achieved with this new dye, compared to 6.3% for N3 dye under the same experimental conditions. Although these indoline dyes are slightly less efficient than N3 dye, the cost of indoline dye is much less than for N3 due to ease of preparation. Furthermore, indoline dyes are shown to be highly stable to photoredox processes by cyclic voltammogram.     

Phenothiazine derivatives for efficient organic dye-sensitized solar cells

Novel organic dyes based on the phenothiazine (PTZ) chromophore were designed and synthesized for dye-sensitized solar cells, which give solar energy-to-electricity conversion efficiency (eta) of up to 5.5% in comparison with the reference Ru-complex (N3 dye) with an eta value of 6.2% under similar experimental conditions.     

Coplanar indenofluorene-based organic dyes for dye-sensitized solar cells

A series of new organic dyes, comprising indenofluorene moiety as a conjugated bridge, with an extended π-groups, such as thiophene and furan, diphenylamine as donor, cyanoacrylic acid group as an electron acceptor and anchoring group, have been synthesized. Photophysical and electrochemical measurements, and theoretical computation were carried out on these dyes. Dye-sensitized solar cells (DSSCs) using these dyes as the sensitizers exhibited photocurrent density (J_SC), open-circuit voltage (V_OC), and fill factor (FF) in the range of 6.95–8.20 mA/cm², 0.70–0.71 V, and 0.69–0.71, respectively, corresponding to an overall conversion efficiency of 3.36–4.05%. The best efficiency reached 56% of the standard cell based on N719.     

A fluorene-modified porphyrin for efficient dye-sensitized solar cells

Porphyrins bearing a polyaromatic or a heterocyclic group are prepared to study their fundamental and photovoltaic properties. Solar cells sensitized with a fluorene-modified porphyrin outperform other dyes in the series, reaching ~90% efficiency of N719 dye.     

Novel organic dyes for efficient dye-sensitized solar cells

Two novel metal-free organic dyes containing thienothiophene and thiophene segments have been synthesized. Nano-crystalline TiO2 dye-sensitized solar cells were fabricated using these dyes as light-harvesting sensitizers, and a high solar energy-to-electricity conversion efficiency of 6.23% was achieved.