Tandem Dye-sensitized Solar Cells Research Articles

Molecular Engineering Strategies of Spectral Matching and Structure Optimization for Efficient Metal-Free Organic Dyes in Dye-Sensitized Solar Cells: A Theoretical Study.

Metal-free organic dyes are promising dyes that can be applied widely in dye-sensitized solar cells (DSSCs). The rational design and selection of dyes with complementary absorption can promote the development of methods that can enhance the utilization of incident light by DSSCs, such as cosensitization and tandem devices. Based on these opinions, the structure of the reported high-performance metal-free organic dye ZL003 is used as a template to design two new metal-free organic dyes, HX-1 and HX-2, by replacing its donor unit with a 2-phenothiazine-phenylamine unit and fusing its three independent π-bridge units into a whole with the aim of driving the red shift and the blue shift of the absorption spectra of ZL003, respectively. Through theoretical investigation, it is demonstrated that the perfect complementary optical absorption of HX-1 and HX-2 can be realized as the shift of the absorption spectra of ZL003 to different directions, which means their feasibility to the application in cosensitization or tandem dye-sensitized solar cells (T-DSSCs). Furthermore, it is hypothesized that HX-1 may be the dye with better photovoltaic performance than ZL003 by modeling their intramolecular charge-transfer (ICT) processes, TiO2 surface adsorption, and photovoltaic parameters. The short-circuit current density (Jsc) and photoelectric conversion efficiency (PCE) of HX-1 are 23.10 mA·cm-2 and 21.26% in theory, compared to those of 20.68 mA·cm-2 and 19.64% in ZL003 at the same computational level, respectively. In view of the complementary optical properties, the combination of HX-1 with HX-2 may be a reasonable option for dyes for the development of a highly efficient cosensitization system or T-DSSCs in the future. In terms of such findings, these two novel metal-free organic dyes may have bright prospects in the research of highly efficient DSSCs, and this work can provide a reference for the design of dyes with complementary absorption through simple structural adjustments of the realistic dyes with high photovoltaic performance.

A very simple flexible tandem dye-sensitized solar cell

AbstractDye-sensitized solar cells (DSSCs) have been proposed as the most important third generation photovoltaic devices owing to their low fabrication cost, design flexibility, having low hazard to the environment and ease of construction. Tandem DSSCs (T-DSSC) were said to possess properties of its sensitized photoanode and sensitized photocathode in terms of the power conversion efficiency (PCE) parameters. With less studies on the fabrication of simple a flexible tandem DSSC, this work aims at filling this gap as well as showing the influence of one of the main factors that affect the performance of such a device. In this paper, TiO2 and NiO layers were prepared by blading method, sensitized separately, then sandwiched together. The fabricated device produced short circuit current, open circuit voltage and power conversion efficiency of 0.138 mA.cm−2, 0.942 V and 0.063%, respectively. This simple T-DSSC produced a high photovoltage and showed that the photocurrent produced by each photoelectrode should be identical. This match is to overcome the possible hump in the device performance.

A solid-state p–n tandem dye-sensitized solar cell

First demonstration of a solid-state p–n tandem dye-sensitized solar cell (t-DSC) shows a substantial open-circuit voltage which holds great promise for a wide range of applications, particularly in the fields of photovoltaics and photoelectrochemical devices.

Unveiling a New Frontier in Efficient Solar Power Conversion with a Pioneering Bifacial Tandem Dye-Sensitized Solar Cell

Unveiling a New Frontier in Efficient Solar Power Conversion with a Pioneering Bifacial Tandem Dye-Sensitized Solar Cell

Photoelectrochemical performance of BiOI/TiO 2 nanotube arrays (TNAs) p-n heterojunction synthesized by SILAR-ultrasonication-assisted methods

In order to extend the visible region activity of titania nanotube array (TNAs) films, the successive ionic layer adsorption and reaction (SILAR)-ultrasonication-assisted method has been used to prepare BiOI-modified TiO 2 nanotube arrays (BiOI/TNAs). The band gap of BiOI/TNAs for all the variations reveals absorption in the visible absorption. The surface morphology of BiOI/TNAs is shown in the nanoplate, nanoflake and nanosheet forms with a vertical orientation perpendicular to TiO 2 . The crystalline structure of BiOI did not change the structure of the anatase TNAs, with the band gap energy of the BiOI/TNAs semiconductor in the visible region. The photocurrent density of the BiOI/TNAs extends to the visible-light range. BiOI/TNAs prepared with 1 mM Bi and 1 mM KI on TNAs 40 V 1 h, 50 V 30 min show the optimum photocurrent density. A tandem dye-sensitized solar cell (DSSC)-photoelectrochemical (PEC) was used for hydrogen production in salty water. BiOI/TNAs optimum was used as the photoanode of the PEC cell. The solar to hydrogen conversion efficiency (STH) of tandem DSSC-PEC reaches 1.34% in salty water.

The application of a novel D−A− π − A phenothiazine-based organic dye with N719 in efficient parallel tandem dye-sensitized solar cells

In this study, an innovative D−A− π − A 2-phenothiazine-phenylamine-based organic dye PTZ-15 was synthesized and confirmed to own compatibility and helpfulness with the classical ruthenium dye N719 in the aspect of light-harvesting. Hence, the T-DSSCs with a doubled-sided Pt electrode which were composed of a N719-based top cell and a PTZ-15-based bottom cell in the parallel connection were manufactured and the corresponding performance was tested. The parallel tandem DSSCs (PT-DSSCs) exhibited a substantially increased short-circuit photocurrent density (Jsc) of 20.62 mA·cm−2 and photoelectric conversion efficiency (PCE) of 10.85 % relative to the conventional DSSCs based on single N719 or PTZ-15. In terms of such findings, we afford a strategy for driving the further development of the high-efficient T-DSSCs.

Dye‐Sensitized Solar Cells with Efficiency over 36% under Ambient Light Achieved by Cosensitized Tandem Structure

The cosensitization process is an effective way to improve the performance of dye‐sensitized solar cells (DSSCs), especially for tandem cells that employ the complementary light harvest ranges of different dyes. Herein, various cosensitized DSSCs are prepared using D35, XY1b, and Y123 dyes and employed to construct cobalt tandem DSSCs. First, the performance of single cells with and without scattering layers is studied. The results show that the cosensitized cells using D35 + XY1b and XY1b + Y123 dyes have higher power conversion efficiency (PCE) than the others, attributed to their longer light absorption wavelength and higher charge recombination resistance. Furthermore, the XY1b + Y123 cell has significantly higher open circuit voltage (Voc) but slightly lower current density (Jsc) than those of the D35 + XY1b cell. The cosensitized systems are further utilized to prepare tandem cells. Photoelectrodes without and with scattering layers are used as top and bottom cells, respectively. It shows that by using D35 + XY1b (higher Jsc) and XY1b + Y123 (higher Voc) as sensitizers of top and bottom cells, respectively, a PCE as high as 36.27% can be achieved under fluorescent lighting. The cells using these dyes have high long‐term stability at room temperature.

Pentafluorosulfanyl-functionalised BODIPY push-pull dyes for p-type dye-sensitized solar cells.

We report a push-pull BODIPY-based dye functionalised with an electronegative SF5 group at the meso position for applications in photocathodes in tandem dye-sensitized solar cells (DSSCs). The push-pull character enhances charge-transfer from the mesoporous NiO cathode surface towards the redox mediator. A Knoevenagel condensation reaction was used to introduce the carboxylic acid to anchor the dye to the oxide surface, via a styryl linker which increases the conjugation in the molecule and shifts the absorption to the red. The room-temperature synthesis and high yields, make the dye promising for manufacture on a large scale. The dye was applied in p-DSSCs giving a power conversion efficiency (0.066%), a short circuit photocurrent (J SC) of 3.84 mA cm-2, open circuit voltage (V OC) of 58 mV and fill factor of 30%.

A strategy for efficient parallel tandem dye-sensitized solar cells based on doubled-sided Pt electrode with a novel phenothiazine-based dye and N719

The tandem idea of the dye-sensitized solar cells (DSSCs) is considered as a promising route to break through the barrier for the development of the DSSCs through extending the absorption spectra and improving the short-circuit photocurrent density (Jsc) or open-circuit voltage (Voc). In this paper, an innovative 2-phenothiazine-phenylamine-based organic dye PTZ-17 with complementary optical properties to dye N719 was exploited. The parallel tandem dye-sensitized solar cells (PT-DSSCs) with a doubled-sided Pt electrode which are composed of a N719-based top cell and a PTZ-17-based bottom cell were manufactured and exhibited a high photoelectric conversion efficiency of 10.52%. From our work, a new strategy is provided for the further exploration of the dye molecular selection and the high-efficient DSSCs preparation.

Push-Pull Phenoxazine-Based Sensitizers for p-Type DSSCs: Effect of Acceptor Units on Photovoltaic Performance.

Finding new efficient p-type sensitizers for NiO photocathodes is a great challenge for the development of promising low-cost tandem dye-sensitized solar cells (DSSCs). Now, the focus of researchers investigating these cells has been to create high-performance p-type systems. With this intention, herein, the design and synthesis of six new phenoxazine-based donor-acceptor (D-A)-configured organic dyes PO1-6 was reported, comprising different acceptor moieties specially designed for the sensitization of mesoporous p-type semiconductor NiO for the construction of p-type DSSCs (p-DSSCs). This work includes structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies of these dyes, including evaluation of their structure-property relationships. The optical studies revealed that PO1-6 displayed adequate absorption and emission features in the range of 480-550 and 560-650 nm, respectively, with a bandgap in the order of 2.05-2.40 eV, and their thermodynamic parameters favored an efficient interfacial charge transfer involving NiO. Among the six new dyes, the device based on sensitizer PO2 carrying electron-withdrawing 1,3-diethyl-2-thiobarbituric acid achieved the highest power conversion efficiency of 0.031 % (short-circuit current density=0.89 mA cm-2 , open-circuit voltage=101 mV, and fill factor=35 %). Conclusively, the study furnishes an understanding of the intricacies involved in the structural modification of phenoxazine-based sensitizers to further ameliorate the performance of the p-type DSSCs.

Tandem dye-sensitized solar cells with efficiencies surpassing 33% under dim-light conditions

To fabricate dye-sensitized solar cells (DSSCs), the variation of TiO2 film thickness elicits contrary effects on the light-harvesting and charge transfer, thereby affecting cell performance. To compromise the TiO2 thickness on the two effects, tandem DSSCs constructed by stacking two cells in series were proposed herein. Cells with high transparent photoelectrodes and counter electrodes were employed as the top cells; thus, the light unabsorbed by the top cells can be transmitted through, and harvested by the bottom cells. Furthermore, cobalt redox couple was adopted to decrease the light loss caused by absorption of the electrolyte. By regulating the film thicknesses of the top and bottom cells, both light harvest and charge transfer performance can be improved simultaneously, thereby, achieving a conversion efficiency as high as 33.98% under 2000 lx fluorescent lighting. This efficiency is much higher than the value (26.57%) obtained by the single cell. The tandem structure can also be applied under sunlight conditions, which can increase the efficiency from 9.27% to 11.31%.

High-Efficiency (Over 10%) Parallel Tandem Dye-Sensitized Solar Cells Based on Tri-Carbon Electrodes

Ensuring high power conversion efficiency, partially or completely replacing Pt electrodes with inexpensive materials is one of the important development directions of dye-sensitized solar cells (DSSCs). In this work, we have developed a three-component (MWCNTs, carbon black and graphite) carbon (tri-carbon) electrode material for DSSC devices combined with the advantages of high electron transfer kinetics of MWCNTs, plentiful catalytic sites in crystal edges of carbon black and superior electrical conductivity and catalytic activity of graphite. Using a tri-carbon electrode, a Pt electrode, and two N719-sensitized photoanodes, a parallel tandem dye-sensitized solar cells are assembled obtaining a high PCE of 10.26% (Voc = 0.70 V, Jsc = 19.99 mA/cm2, FF = 73.33%). It opens up a new avenue for the development of low-cost and high-performance DSSCs.

Assessing the effect of surface states of mesoporous NiO films on charge transport and unveiling an unexpected light response phenomenon in tandem dye-sensitized solar cells

The effect of surface states of mesoporous NiO films on charge transport and an unexpected light response phenomenon in tandem dye-sensitized solar cells has been investigated.

Tandem Dye-Sensitized Solar Cells with Efficiencies Surpassing 33% Under Dim-Light Conditions

Tandem Dye-Sensitized Solar Cells with Efficiencies Surpassing 33% Under Dim-Light Conditions

Switching the electrical characteristics of TiO2 from n-type to p-type by ion implantation

For many applications, as for example tandem dye-sensitized solar cells (DSSCs), the development of transparent p-type semiconductor with good charge transport properties is crucial. In this work, a nitrogen-doped TiO2 material is transformed by ion implantation into an efficient hole transport layer that could reduce the electron-hole recombination processes in the devices. Theoretical calculations allowed to demonstrate that the position of nitrogen species as well as their respective ratio impact the optical and electrical properties of N-doped TiO2 materials. The chemical composition was therefore tuned by the ion implantation parameters, achieving a high transparency in the UV–visible region while generating delocalized states near the top of the valence band that do not act as traps. In terms of electrical properties, beyond the possibility to tune the electrical behavior of TiO2 from n-type to p-type upon nitrogen doping, we succeed to increase the conductivity by a higher electron mobility without change in their density, which is of prime interest for charge transport application.

NiO/ZrO2 nanocomposites as photocathodes of tandem DSCs with higher photoconversion efficiency with respect to parent single-photoelectrode p-DSCs

Tandem dye-sensitized solar cell shows higher photoconversion performances with respect to parent devices with single photoactive electrode thanks to careful photocurrent matching and complementarity of electrodes optical absorption.

A High-Field Anodic NiO Nanosponge with Tunable Thickness for Application in p-Type Dye-Sensitized Solar Cells

Dye-sensitized photocathodes have the potential to significantly contribute to the efficiency of the solar light-to-current conversion in tandem dye-sensitized solar cells (DSSCs). A novel, highly ...

Toward Current Matching in Tandem Dye-Sensitized Solar Cells.

The tandem pn-type dye-sensitized solar cells (pn-DSCs) have received much attention in the field of photovoltaic technologies because of their great potential to overcome the Shockley-Queisser efficiency limitation that applies to single junction photovoltaic devices. However, factors governing the short-circuit current densities (Jsc) of pn-DSC remain unclear. It is typically believed that Jsc of the pn-DSC is limited to the highest one that the two independent photoelectrodes can achieve. In this paper, however, we found that the available Jsc of pn-DSC is always determined by the larger Jsc that the photoanode can achieve but not by the smaller one in the photocathode. Such experimental findings were verified by a simplified series circuit model, which shows that a breakdown will occur on the photocathode when the photocurrent goes considerably beyond its threshold voltage, thus leading to an abrupt increase in Jsc of the circuit. The simulation results also suggest that a higher photoconversion efficiency of the pn-DSCs can be only achieved when an almost equivalent photocurrent is achieved for the two photoelectrodes.

Low lying valence band edge materials based on copper oxide for tandem dye-sensitized solar cells

For enhancing the photovoltaic performance of tandem dye-sensitized solar cell (DSSC), a new perspective is proposed to develop a novel material with a lower valence band edge in alternative to the low-performing p-type semiconductor oxides. Copper oxide (Cu2O/CuO) materials were synthesized by a facile and near room-temperature wet chemical precipitation synthesis. The lowest reported lying valence band edge along with 2.10 V of the open circuit voltage (VOC) in a hypothetical tandem-DSSC certainly had demonstrated the suitability of these materials for the design of highly efficient photocathodes in tandem architecture. To illustrate the potential of a tandem-DSSC built with this material and TiO2, further efforts will be devoted to design and synthesize new suitable organic dyes and electrolytes.

Can a temporary bond between dye and redox mediator increase the efficiency of p-type dye-sensitized solar cells?

Efficient n-type dye-sensitized solar cells are known since the seminal work of O'Reagan and Grätzel in 1991. However, highly efficient p-type dye-sensitized solar cells have not been developed so far. This hinders the construction of tandem dye-sensitized solar cells, which can surpass the performance of n-type devices. Within this work, we investigate if a temporary coordination of transition metal-based redox mediators at a sensitizer can increase the efficiency of p-type dye-sensitized solar cells. Based on a computational screening, diverse Cu, Ni, and Co redox mediators were selected to construct p-type dye-sensitized solar cells. Unfortunately, the efficiency of the investigated devices does not surpass analogous cells with iodide-triiodide as redox mediator. While Ni and Cu complexes might be reduced to Ni(0) and Cu(0), respectively, the investigated Co-complex quenches the excited state efficiently. As a result, the necessary electron injection from the semiconductor is too slow, which hinders the construction of a highly efficient p-type dye-sensitized solar cell. Graphical Abstract Comparison of the mode of action of p-type dye-sensitized solar cells. While top shows the traditional one, bottom shows the investigated devices where a temporary link between dye and redox mediator plays a crucial role.