Photocurrent Of Dye-sensitized Solar Cells Research Articles

Comments on: Enhancing photocurrent of dye-sensitized solar cells through solvent modulating aggregation of dyes [Solar Energy 240 (2022) 157–167; https://doi.org/10.1016/j.solener.2022.05.032

Comments on: Enhancing photocurrent of dye-sensitized solar cells through solvent modulating aggregation of dyes [Solar Energy 240 (2022) 157–167; https://doi.org/10.1016/j.solener.2022.05.032

Enhancing photocurrent of dye-sensitized solar cells through solvent modulating aggregation of dyes

Aggregation of organic molecules plays a key role in determining the photoelectronic properties of various devices. However, the formation of aggregates is an outcome of complex synergistic effects of various intermolecular forces, and changes with the molecular structure and environment. Here we exploit the aggregation of two dyes with (MTPABT-Pyc) or without (MTPAcc) the nanosecond long-lived charge separation state and their effect on photovoltaic performance of dye-sensitized solar cells (DSSCs). Different solvent systems were selected to modulate the interactions between solvents and dye molecules for the effects on photophysical processes. Combining the experimental results on the solvent effect on dye aggregation with theoretical calculations reveals that MTPAcc inclines to form H-aggregation on the TiO2 surface because of the decisive role of its molecular structure. The solvent regulation has a great impact on MTPABT-Pyc which can make aggregates transform between H-aggregation and J-aggregation. The effects of aggregation on the device performance of two dyes are completely opposite. High performance of MTPAcc depends on the co-adsorbent chenodeoxycholic acid, which could suppress the dye aggregation. In contrast, the aggregation of MTPABT-Pyc will not harm the charge separation and transportation processes in devices and shows a positive effect on the cell performance due to the aggregation exhibiting broader absorption bands. As the photocurrent contribution by the aggregation-induced long-wavelength absorption increases from 9% (H-aggregation) to 34% (J-aggregation), the short-circuit current (Jsc) and the power conversion efficiency (PCE) of MTPABT-Pyc increased by 13% and 14%, respectively. These results pave a new way for taking full advantage of the aggregation of molecules to realize high-performance light-to-current conversion.

Modelling of Diffusion-Limited Growth in the Electrodeposition of Porous ZnO

Electrodes of ZnO sensitized with appropriate dyes are very suitable as photoanodes in dye-sensitized solar cells (DSSCs).1 They are of particular advantage relative to established photoanodes based on nanoparticulate TiO2 since they- can be processed at low temperature and- provide higher electron mobility.Processing at low temperature is beneficial in itself because it leads to lower energy consumption during preparation and, hence, helps to reach payback times. Further, it allows using plastic foils as substrates and, thereby, further improves the energy balance and allows constructing lightweight and mechanically flexible solar cells. The higher electron mobility in ZnO helps to reduce the transport resistance in films which becomes important to suppress recombination in DSSCs using reversible redox shuttles to achieve higher photovoltage and, hence, higher efficiency.The electrodeposition of porous ZnO was optimized1 by addition of structure-directing agents (SDAs) in a reaction sequenceO2 + 2 H2O + 4 e- → 4 OH- (1)Zn2+ + 2 OH- → [Zn(OH)2] → ZnO + H2O (2)in which the growth rate of porous ZnO is limited by the diffusion of O2. Optimization of porosity and pore radius of ZnO essential for its application in dye-sensitized solar cells in order to enhance the cell performance can be obtained by proper choice of SDAs. Larger pores, e.g., showed a significantly decreased impedance of mass transport leading to an increased photocurrent in DSSCs. Successful application of these new ZnO films in dye-sensitized solar cells confirmed improved pathways for large complex ions as redox shuttles through the ZnO pore structure.2 Further optimization of film growth requires appropriate modelling. Simulations and experiments are presented for electrodeposition on microstructured electrode arrays (MEAs), namely, parallel band electrodes as model for planar substrates. Microelectrodes are very attractive in electrochemical applications because of easily reached high current densities and fast establishment of a steady state. In the present case of band arrays, however, the overlap of diffusion layers of adjacent electrodes has to be considered and leads to a reduced mass flux to each individual electrode band in comparison to a single electrode. A lower current density and, hence, lower rate of electrodeposition is observed. Three consecutive steps in the build-up of diffusion profiles have been established in the literature: at the beginning, each electrode band can be treated separately, then the overlap has to be considered and finally the diffusion profile can be described as planar, well comparable to a macroscopic electrode. Simulations were performed considering the detailed distribution of concentration changes in the electrolyte and also including all changes brought forward by the deposition of material (see Figure) and, hence, changes of the electrode geometry.3 The simulated current densities and the simulated shape of electrodeposited films compared very well to experimentally observed values, proving the validity of the chosen approach. 1. T. Yoshida, J. B. Zhang, D. Komatsu, S. Sawatani, H. Minoura, T. Pauporte, D. Lincot, T. Oekermann, D. Schlettwein, H. Tada, D. Wöhrle, K. Funabiki, M. Matsui, H. Miura, H. Yanagi, "Electrodeposition of Inorganic/Organic Hybrid Thin Films", Adv. Funct. Mat. (2009) 19, 17-43.2. T. H. Q. Nguyen, R. Ruess, D. Schlettwein, "Adjusting Porosity and Pore Radius of Electrodeposited ZnO Photoanodes", J. Electrochem. Soc. (2019) 166, B3040-B3046.3. C. Lupó, D. Schlettwein, "Modeling of Dendrite Formation as a Consequence of Diffusion-Limited Electrodeposition", J. Electrochem. Soc. (2019) 166, D3182-D3189.Figure: Simultaneously obtained modelling results of interdependent electrodeposition of porous ZnO (in grey) and concentration changes of O2 in the electrolyte (red for high, blue for low concentrations) after 100 s of electrodeposition under diffusion limitation. Figure 1

Preparation of Nano-Ag-TiO2 Composites by Co-60 Gamma Irradiation to Enhance the Photocurrent of Dye-Sensitized Solar Cells

Nano-silver-titanium dioxide (Ag-TiO2) composites were prepared from commercial TiO2 (P25, Degussa) and silver nitrate (AgNO3) by gamma Co-60 irradiation method with various initial concentrations of AgNO3. The nano-AgTiO2 composites are utilized as the photoanode for dye-sensitized solar cells (DSCs). Under full sunlight illumination (1000 W/m2, AM 1.5), the efficiency of DSCs has improved significantly despite the Ag content of below 1%. The DSC—assembled with 0.75 Ag-TiO2 (0.75% Ag) photoanode—showed that the photocurrent was significantly enhanced from 8.1 mA.cm−2 to 9.5 mA.cm−2 compared to the DSCs using bared TiO2 photoanode. The unchanged open-circuit voltage resulted in the overall energy conversion efficiency to be increased by 25% from 3.75% to 4.86%. Electrochemical impedance spectroscopy (EIS) analysis showed that the charge transfer resistance is reduced when increasing Ag content, demonstrating that the charge transfer at TiO2/dye interface was enhanced in the presence of silver nanoparticles.

Dimethylammonium Iodide: Boosting Photocurrent for Dye-sensitized Solar Cells with Perovskite Precursors Electrolyte

Dimethylammonium Iodide: Boosting Photocurrent for Dye-sensitized Solar Cells with Perovskite Precursors Electrolyte

Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect.

A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-π-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pre-treatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte-induced dye reorganization at the surface.

Near-infrared quantum-cutting and long-persistent phosphor Ca3Ga2Ge3O12: Pr3+, Yb3+ for application in in vivo bioimaging and dye-sensitized solar cells

Either quantum-cutting luminescence (QCL) or long-persistent luminescence (LPL) phosphor has been attracted attention for practical applications. Due to the real-time excitation source (low efficiency) for the QCL (LPL) process, both QCL and LPL have their own shortcomings. By combining the inherent properties of QCL and LPL, we devise a concept of QCLPL (quantum cutting long persistent luminescence), which can obtain high efficient LPL (at least > 100%). Germinate Ca3Ga2Ge3O12 (CGG) is chosen as matrix due to its low phonon frequency. Pr3+ is selected as donor (D) ion owing to its ladder-like arranged energy levels which facilitate the photon absorption and subsequent energy transfer (ET). Yb3+ ion is codoped as acceptor (A) ion due to its absorption and emission in near-infrared (NIR) region. Since the “optical transmission window” of biological tissues within 700–1100 nm allows for deeper light penetration, the QCLPL CGG: Pr3+, Yb3+ (CGGPY) results in increasing bioimage contrast. Meanwhile, as a down-conversion luminescent medium, CGGPY transfers UV light to NIR light, which increases the solar light harvest and photocurrent of dye-sensitized solar cells (DSSCs). Altogether, the strategy of combination of QCL and LPL processes in one host lattice has important implications for infrared lighting, DSSCs, bioimaging and et al.

Magnetic field effects in dye-sensitized solar cells controlled by different cell architecture.

The charge recombination and exciton dissociation are generally recognized as the basic electronic processes limiting the efficiency of photovoltaic devices. In this work, we propose a detailed mechanism of photocurrent generation in dye-sensitized solar cells (DSSCs) examined by magnetic field effect (MFE) technique. Here we demonstrate that the magnitude of the MFE on photocurrent in DSSCs can be controlled by the radius and spin coherence time of electron-hole (e-h) pairs which are experimentally modified by the photoanode morphology (TiO2 nanoparticles or nanotubes) and the electronic orbital structure of various dye molecules (ruthenium N719, dinuclear ruthenium B1 and fully organic squaraine SQ2 dyes). The observed MFE is attributed to magnetic-field-induced spin-mixing of (e-h) pairs according to the Δg mechanism.

A novel TiO2 film photoanode decorated with spirulina-derived residual groups for enhanced photocurrent in dye-sensitized solar cells

Spirulina-derived residual groups as a special additive to modify the dyed-TiO2/electrolyte interface are introduced to enhance the photovoltaic performance. The interaction between the spirulina residual groups and surface of TiO2 films is investigated. It is found that spirulina extracts molecule split into several small fragments as TiOCH2OH anchoring on the surface of TiO2 by thermal treatment. Spirulina residual groups modified TiO2 photoanodes have a higher light-harvesting capacity and efficient electron transport. As a result, both the Voc and Jsc are improved by TiO2 photoanodes decorated with spirulina derived residual groups, with the short-circuit current of 10.17mAcm−2 corresponding to the photoelectric conversion efficiency of 4.26%, which is 33.1% higher than the blank DSSC.

High Performance Dye-Sensitized Solar Cells with Enhanced Light-Harvesting Efficiency Based on Polyvinylpyrrolidone-Coated Au-TiO2 Microspheres.

Surface plasmon resonance using noble metal nanoparticles is regarded as an attractive and viable strategy to improve the optical absorption and/or photocurrent in dye-sensitized solar cells (DSSCs). However, no significant improvement in device performance has been observed. The bottleneck is the stability of the noble-metal nanoparticles caused by chemical corrosion. Here, we propose a simple method to synthesize high-performance DSSCs based on polyvinylpyrrolidone-coated Au-TiO2 microspheres that utilize the merits of TiO2 microspheres and promote the coupling of surface plasmons with visible light. When 0.4 wt % Au nanoparticles were embedded into the TiO2 microspheres, the device achieved a power conversion efficiency (PCE) as high as 10.49%, a 7.9% increase compared with pure TiO2 microsphere-based devices. Simulation results theoretically confirmed that the improvement of the PCE is caused by the enhancement of the absorption cross-section of dye molecules and photocurrent.

Significant improvement of photocurrent in dye-sensitized solar cells by incorporation thiophene into electrolyte as an inexpensive and efficient additive

For the first time, thiophene as an efficient additive is applied in electrolyte of dye-sensitized solar cells (DSSCs). In the cell based on 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid (TPA) sensitizer, addition of 1 M thiophene to the electrolyte (instead of 4-tert-butylpyridine (TBP)) increases significantly photocurrent density (Jsc) from 4.62 to 7.80 mA cm−2. Consequently, overall conversion efficiency (η) enhances from 2.17% to 3.18% with a 46% improvement. For DSSC based on 2-cyano-3-(2′-(5′,10′,15′,20′-tetraphenylporphyrinato zinc(II))yl)acrylic acid (Zn-1) with modified electrolyte, Jsc increases from 4.18 to 8.23 mA cm−2 and η improves from 1.46% to 1.96% that shows an enhancement of 34% in η. Intensity modulated photocurrent spectroscopy (IMPS) indicates the faster electron transfer in the DSSC based on thiophene additive compared to the standard device. Also, the higher electron diffusion coefficient (Dn) of the DSSC with modified electrolyte shows the thiophene additive facilitates the electron transfer. Based on cyclic voltammetry (CV) and UV–vis data, thiophene forms a molecular complex with iodine molecule in the electrolyte solution that has a remarkable effect on the redox couple oxidation–reduction reactions which improves Jsc. A significant improvement in Jsc with a small decrease in Voc and thereby an increase in η are observed from addition thiophene.

Hierarchical TiO2 submicron-sized spheres for enhanced power conversion efficiency in dye-sensitized solar cells

Hierarchical TiO2 submicron-sized spheres (TiO2 HSSs) with diameters of 400–600nm were synthesized by a facile one-step solvothermal method in ethanol solvent. The HSSs composed of nanoparticles of ∼14nm have a relatively large surface area of ∼35m2/g. When applied as the scattering overlayer in dye-sensitized solar cells (DSCs), such TiO2 HSSs effectively improved light harvesting and led to the increase of photocurrent in DSCs. Furthermore, bilayer-structured photoanode also provided fast electron transportation and long electron lifetime as confirmed by electrochemical impedance spectra. As a result, DSC based on P25 nanoparticle underlayer and HSS-2 overlayer exhibited the highest cell efficiency (6.23%) compared with ones with pure P25 (5.50%) or HSS-2 (2.00%) photoanodes.

Stable Plasmonic-Improved dye Sensitized Solar Cells by Silver Nanoparticles Between Titanium Dioxide Layers

Novel metal nanoparticles (NPs) are introduced as light-harvesting antennae to enhance photocurrent of photovoltaic cells. In this work, we examined the plasmonic enhancement of photocurrent in dye-sensitized solar cells with deposition of Ag NPs between different TiO2 layers. The I–V measurement showed clearly that the open-circuit voltage (VOC) of cells doesn't depend on Ag existence in our cells configuration extremely, however the short-circuit photocurrent density (JSC) strongly depends on it. Deposition of Ag NPs on packing TiO2 layer (T1) and transparent layer of TiO2 (T2) both had acceptable results. The solar cells performance by treatment of Ag was studied and the results indicated that time treatment of AgNO3 and KBH4 is a key parameter which has effect on the PCE of the device. Low time (1min), hardly shows any effect while medium time (2min) shows significant effect on device performance. Meanwhile to improve the stability of these cells, we have proposed a new sealing method to fabricate promising stabile dye synthesized solar cells.

Influence of number of benzodioxan-stilbazole-based ancillary ligands on dye packing, photovoltage and photocurrent in dye-sensitized solar cells.

Two novel heteroleptic Ru(II) bipyridyl complexes, HD-2 and HD-2-mono, were molecularly engineered, synthesized and characterized for dye-sensitized solar cells (DSCs). The influences of mono versus bis electron-donor benzodioxan ancillary ligands on optical, dye packing, electrochemical and photovoltaic properties were examined and compared to the benchmark N719. HD-2 and HD-2-mono achieved solar-to-power conversion efficiencies (%η) of 9.64 and 9.50, respectively, compared to 9.32 for N719 under the same experimental device conditions. Optical results showed that HD-2 and HD-2-mono have much higher molar extinction coefficients, longer excited state lifetimes and narrower HOMO-LUMO gaps compared to N719. Although the molar extinction coefficient of HD-2-mono was 27% less than that of HD-2, it outperformed HD-2 in photovoltaic performance when anchored on TiO2, owing to better dye packing and loading of the former. Charge recombination at the dye/TiO2 interface by impedance spectroscopy analysis showed that the recombination resistance and the lifetime of injected electron in TiO2 conduction band is directly proportional to the open-circuit voltage (Voc) observed. Furthermore, compared to HD-2 and HD-2-mono, the greater Voc of N719 can be attributed to the greater negative free energy for dye regeneration. Both HD-2 and HD-mono have almost the same negative free energy, which explains why they achieved almost the same Voc. Decay dynamic analysis for solar devices fabricated from the named dyes, by time correlated single photon counting (TCSPC), elucidated that the lowest excited state decay lifetime for HD-2-mono, HD-2 and N719 are 3, 10 and 20 ps, respectively. The shorter the decay lifetime, the less kinetic redundancy, which leads to better photocurrent, and that explanation is consistent with the measured photocurrent and total solar-to-power conversion efficiency of the named dyes in the order of HD-2-mono > HD-2 > N719.

Enhancement of Photocurrent in Dye-Sensitized Solar Cells Using Bismuth Doped TiO2- Graphene as a Hot Carrier Transport

Enhancement of Photocurrent in Dye-Sensitized Solar Cells Using Bismuth Doped TiO2- Graphene as a Hot Carrier Transport Dye-sensitized solar cells (DSSCs) are of tremendous current interest, but they suffer from a lack of ability to harness the majority of visible light, or require heavy metal addition such as Pb or Cd which are not considered environmentally friendly. By decorating doped metal oxides such as titania with earth abundant and friendly metals on functionalized graphene sheets (FGSs), functional mats are enabled for enhanced light harvesting. In this work, novel highly crystalline bismuth doped TiO2 nanocrystals were prepared successfully by a facile sol-gel hydrothermal process and attached to FGS’s to make functional catalyst mats.

Dual functions of YF3:Eu3+ for improving photovoltaic performance of dye-sensitized solar cells

In order to enhance the photovoltaic performance of dye-sensitized solar cell (DSSC), a novel design is demonstrated by introducing rare-earth compound europium ion doped yttrium fluoride (YF3:Eu3+) in TiO2 film in the DSSC. As a conversion luminescence medium, YF3:Eu3+ transfers ultraviolet light to visible light via down-conversion, and increases incident harvest and photocurrent of DSSC. As a p-type dopant, Eu3+ elevates the Fermi level of TiO2 film and thus heightens photovoltage of the DSSC. The conversion luminescence and p-type doping effect are demonstrated by photoluminescence spectra and Mott-Schottky plots. When the ratio of YF3:Eu3+/TiO2 in the doping layer is optimized as 5 wt.%, the light-to-electric energy conversion efficiency of the DSSC reaches 7.74%, which is increased by 32% compared to that of the DSSC without YF3:Eu3+ doping. Double functions of doped rare-earth compound provide a new route for enhancing the photovoltaic performance of solar cells.

Functionalized multi-walled carbon nanotubes for enhanced photocurrent in dye-sensitized solar cells

The influence of the incorporation of nitric acid-treated (functionalized) multi-walled carbon nanotubes (f-MWCNTs) and unmodified MWCNTs in TiO2 films are investigated by observing the photocurrent-voltage characteristics of dye-sensitized solar cells (DSSCs) with and without MWCNTs. The short-circuit photocurrent (Jsc) of the modified DSSC increased by 46% compared with that of a cell with plain TiO2 film. The open-circuit voltage remained the same for all cases. The enhanced Jsc is explained by the increased surface area of the film, enhanced cluster formation of TiO2 particles around f-MWCNTs, and improved interconnectivity of TiO2 particles in the presence of f-MWCNTs. The efficiency of the cell increased by 45% due to Jsc enhancement.

A novel biomass coated Ag–TiO2 composite as a photoanode for enhanced photocurrent in dye-sensitized solar cells

A novel biomass-coated Ag nanoparticle-modified TiO2 composite was prepared and used as a photoanode in a dye-sensitized solar cell with a high surface area, strong light scattering and efficient electron transport. It was found that syzygium extract has an appreciable effective function as a reducing and stabilizing agent simultaneously. The mean size of the synthesized silver nanoparticles is 4.0 ± 0.7 nm measured on the TEM images. Residual hydroxyl groups of the biomass on the photoanode improve dye absorption and electron injection efficiency. The syzygium-Ag–TiO2 DSSC exhibits the best performance with a short-circuit current of 11.8 mA cm−2 corresponding to a photoelectric conversion efficiency of 5.12%, which is higher than the glucose-Ag–TiO2 and UV-Ag–TiO2 DSSCs, and much higher than the blank DSSC.

Photovoltaic performance of bifacial dye sensitized solar cell using chemically healed binary ionic liquid electrolyte solidified with SiO2 nanoparticles

In this study, we investigated the effect of electrolyte composition, photoanode thickness, and the additions of GuSCN (guanidinium thiocyanate), NMB (N-methylbenimidazole), and SiO2 on the photovoltaic performance of DSSCs (dye sensitized solar cells). A bifacial DSSC is realized and irradiated from front and rear sides. The devices give maximum photovoltaic efficiencies for 70% PMII (1-propyl-3-methyl-imidazolium iodide)/30% (EMIB(CN)4) (1-ethyl-3-methyl-imidazolium tetracyanoborate) electrolyte composition and 10μm thick photoanode coating which is considered to be the ideal coating thickness for the diffusion length of electrolyte and dye absorption. A significant increase in the photocurrent for DSSCs with optimum molarity of 0.1M GuSCN was observed due to decreased recombination which is believed to be surface passivation effect at photoanode electrolyte interface suppressing recombination rate. Moreover, optimum NMB molarity was found to be 0.4 for maximum efficiency. Addition of SiO2 to the electrolyte both as an overlayer and dispersed particles enhanced rear side illuminated cells where dispersed particles are found to be more efficient for the front side illuminated cells due to additional electron transport properties. Best rear side illuminated cell efficiency was 3.2% compared to front side illuminated cell efficiency of 4.2% which is a promising result for future rear side dye sensitized solar cell applications where front side illumination is not possible like tandem structures and for cells working from both front and rear side illuminations.

Newly designed dye-sensitized solar cells fabricated with double-layered TiO2 (bottom layer)/Bx–TiO2 (top layer) combined electrodes for improved photocurrent

An unusual double-layered TiO2 (bottom layer)/Bx–TiO2 (top layer) combined electrode array was investigated to improve the photocurrent in dye-sensitized solar cells (DSSCs). A positive semiconductor, Bx–TiO2, with nanometer-sized B (1.0, 5.0, and 10.0mol%)-incorporated TiO2 prepared using a solvothermal method, was utilized as the working electrode material by coating onto the second level above the TiO2 electrode. The photocurrent and photovoltaic efficiency of the TiO2 (bottom)/Bx–TiO2 (top)-DSSC were 20.5% and 17.3% greater, respectively, than that of the double-layers of anatase TiO2–DSSC in the photocurrent–voltage (I–V) curve of the optimal electrode. This result was attributed to their energy levels of reduction (LUMO)/oxidation (HOMO) as determined by cyclic voltammetry (CV). As the LUMO level of Bx–TiO2 was located at a slightly higher level than that of pure anatase TiO2, the electrons donated from the dye were easily transferred to the surface of the TiO2 electrode without electron loss. Moreover, the recombination was also much slower in the TiO2 (bottom)/Bx–TiO2 (top)-based DSSCs than in the double-layered pure TiO2 DSSC.