Performance Of Dye-sensitized Solar Cells Research Articles

Investigation of dye-sensitized solar cell performance based on vertically aligned TiO2 nanowire photoanode

In this work, we present our results related to the development of Dye-Sensitized Solar Cells (DSSCs) based on vertically aligned TiO2-nanowire (NW) and Ag nanoparticle (NP) assisted vertically aligned TiO2-NW (TAT) photoanode fabricated by the glancing angle deposition (GLAD) technique on fluorine doped thin oxide (FTO) substrates. The scanning electron microscopy (SEM) analysis reveals that the Ag-NP assisted vertically aligned TiO2-NW photoanode was successfully deposited on FTO substrates. The average length and diameter of the NW have been measured to be ~ 350 nm and ~ 90 - 100 nm, respectively. Moreover, transmission electron microscopy (TEM) and X-ray diffraction (XRD) manifest the presence of small crystals of TiO2 and Ag. Further, the absorption spectrum analysis reveals that the incorporation of Ag-NP in TiO2-NW increases absorption in the visible region, but decreases the efficiency of the cell after the incorporation of the nanoparticle. The calculated bandgap of the annealed Ag-NP (30 nm) assisted TiO2-NW (TAT@30nm) sample from the photoluminescence (PL) graph is ~ 3.12 eV. Finally, it is observed that the TiO2-NW based DSSC device shows better performance in terms of photo conversion efficiency (PCE) compared to the TAT@30nm photoanode based device, with an efficiency of ~0.61 % from the former and ~ 0.24 % from the latter. This reduction in the efficiency of TAT@30nm based devices is due to the larger size of Ag-NP, in which the nanoaprticle acts as an electron sink and acts as a blocking layer.

Predicting the dye-sensitized solar cell performance of novel linear carbon chain-based dyes: insights from DFT simulations.

In this paper, we employ density functional theory (DFT) simulations to predict the energy conversion efficiency of a novel class of organic dyes based on linear carbon chain (LCC) linkers for application in dye-sensitized solar cells (DSSCs). We investigate the role of the anchoring group, which serves as a bridge connecting the linker and the surface. Specifically, we compare the performance of cyanoacrylic acid, dyes PY-4N and PY-3N, with that of phosphonate derivatives, dyes PY-4NP and PY-3NP, wherein the carboxylic group of the cyanoacrylic moiety is replaced with phosphonic acid. The observed variations in the UV/VIS absorption spectra have a slight impact on the light harvesting efficiency (LHE). Based on the empirical parameters we have taken into account, the electron injection efficiency (Φinj) and electron collection efficiency (ηcoll) values do not impact the short-circuit current density (JSC) values of all the studied dyes. The open-circuit voltage (Voc) is theoretically predicted using the improved normal model (INM) method. Among the dyes, PY-4N and PY-3N demonstrate the highest Voc values. This can be attributed to a more favorable recombination rate value, which is related to the energy gap between the HOMO level of the dyes and the conduction band minimum (CBM) of the surface. Dyes PY-4N and PY-3N are predicted to demonstrate remarkably high photoelectric conversion efficiency (PCE) values of approximately 21.79% and 16.52%, respectively, and therefore, they are expected to be potential candidates as organic dyes for applications in DSSCs. It is worth noting that PY-4NP and PY-3NP exhibit strong adsorption energy on the surface and interesting PCE values of 11.66% and 8.29%, respectively. This opens up possibilities for their application in DSSCs either as standalone sensitizers or as co-sensitizers alongside metal-free organic dyes or organic-inorganic perovskite solar cells.

Enriched visible light absorption by Au-embedded Sm3+ doped TiO2 compact photoanode for enhanced dye-sensitized solar cell performance

The cooperative effect of Samarium (Sm3+)-doped TiO2 and gold nanoparticles (Au NPs) is investigated in this work to explore its potential to boost visible light absorption in dye-sensitized solar cells (DSSC). As Sm3+ exhibits PL emissions at 583 nm, 612.2 nm, 663.6 nm, and 726.3 nm, there is an overlap with the absorption region of the N719 dye and these PL emission wavelengths resulting in a rise in photocurrent density and PCE owing better UV light harvesting. Sm3+ absorption and emissions were boosted by LSPR (Localized surface plasmon resonance) of Au NPs. As a result, the Au NPs embedded Sm-doped TiO2 photoanode-based DSSC capture more visible light. Sm (0.3)-TiO2 based DSSC reports the highest PCE (η:7.2%) among a series of Sm (0.2%, 0.3%, 0.4%, and 0.5% mol) TiO2 concentrations. Further, with the addition of Au NPs into the Sm3+ -doped TiO2, the PCE is enlarged into (η: 8.33%), which is more than 60% higher than TiO2 photoanode-based DSSC (η: 5.58%).

In‐Silico Device Performance Prediction of Cosensitizer Dye Pairs for Dye‐Sensitized Solar Cells

AbstractEndeavors in the field of dye‐sensitized solar cells (DSCs) have shown great promise when adopting a data‐driven approach to materials discovery, such as successful molecular‐scale predictions of light‐harvesting chromophores. However, predictions of DSC dyes would become much more sophisticated if a molecular‐to‐macroscopic DSC device prediction methodology existed. Thereby, a fully computational pipeline is presented that predicts device‐performance parameters of DSCs which contain varying dye combinations. Optimal pairing of complementary dyes is identified via a data‐driven workflow that affords cosensitized DSCs with maximum power‐conversion efficiencies. Six high‐performing DSC dyes are paired with partner dyes that are screened from a database of 8488 compounds using sequential heuristic filters. Existing models that predict short‐circuit‐current density (JSC) and open‐circuit voltage (VOC) parameters are adapted to predict singly sensitized and cosensitized DSC performance. The predictions for Jsc values of singly sensitized devices match experimental literature values with comparable accuracy to more computationally costly methods. Five out of six dye pairings are predicted to have greater JSC values when cosensitized compared to their corresponding singly sensitized devices, including two pairs that show strong Jsc boosts of +13% and +12% when cosensitized. Thus, the prospect of an entirely in‐silico prediction pipeline for DSC performance that can be used to realize the fully automated design of optimized cosensitized DSCs is demonstrated.

Controlling the Layer Thickness of Zinc Oxide Photoanode and the Dye-Soaking Time for an Optimal-Efficiency Dye-Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) were developed by exploiting the photovoltaic effect to convert solar energy into electrical energy. The photoanode layer thickness significantly affects the semiconductor film’s ability to carry electronic charges, adsorb sensitizing dye molecules, and lower the recombination of photo-excited electrons injected into the semiconductor. This study investigated the dependence of the zinc oxide (ZnO) photoanode thin-film thickness and the film soaking time in N719 dye on the photocurrent–voltage characteristics. The ZnO photoanode was applied to glass using the doctor blade method. The thickness was varied by changing the scotch tape layers. The ZnO-based DSSC attained an efficiency of 2.77% with three-layered photoanodes soaked in the dye for three hours, compared to a maximum efficiency of 0.68% that was achieved with three cycles using the dip-coating method in other research. The layer thickness of the ZnO photoanode and its optimal adsorption time for the dye are important parameters that determine the efficiency of the DSSC. Therefore, this work provides important insights to further improve the performance of DSSCs.

Morphological evolution of sol-electrophoretic deposited ZnO nanostructures on anodic TiO2 nanotubes for back-side illuminated dye-sensitised solar cells

Efficient photoanodes are essential for dye-sensitized solar cells (DSSCs). We report on sol-electrophoretic deposition of ZnO/TiO2 heterojunction structures with enhanced photocurrent-photovoltage performance for back-side illumination DSSCs. An anodic oxidation method was used for the preparation of TiO2 nanotube arrays (TNAs). ZnO nanostructures with different morphologies were successfully deposited on TNAs via sol-electrophoretic process. The results revealed that TNAs decorated with ZnO favors the photovoltaic properties reaching the best photoanode performance in a pH and temperature of 8.5 and 30°C, respectively, under an electrophoretic deposition (EPD) potential of 10 V. This photoanode generates short circuit current (Jsc) and open circuit voltage (Voc) of 3.28 mA/cm2 and 0.79 V, respectively. Consequently, the power conversion efficiency (PCE) acquired 1.525% with a fill factor of 72% for the best ZnO/TiO2 heterojunction enhances the DSSC performance by 107% with respect to similar TNAs due to the surface passivation of electronic states eliminating the recombination rate.

Improving the Photovoltaic Performance of Dye-Sensitized Solar Cells Using a W and S Co-doped ZnO Photoanode

Improving the Photovoltaic Performance of Dye-Sensitized Solar Cells Using a W and S Co-doped ZnO Photoanode

Rational modification of TiO2 photoelectrodes with spinel ZnFe2O4 and Ag-doped ZnFe2O4 nanostructures highly enhanced the efficiencies of dye sensitized solar cells

To develop effective photoelectrode nanomaterials for dye-sensitized solar cells (DSSCs), spinel ZnFe2O4 (2.5, 5, 7.5, 10 wt%) and Ag-doped ZnFe2O4 (AgxZn1-x/2Fe2O4, x = 0.1, 0.2, 0.3, 0.4 mmol) nanomaterials were added into the TiO2 photoanodes. It was found that the DSSC fabricated with TiO2 + 5 wt% ZnFe2O4 exhibited the most improved efficiency of 3.89 % among the ZnFe2O4 containing devices. Furthermore, the power conversion efficiency (PCE) values were boosted when the Ag+ cations were doped into the ZnFe2O4 crystalline lattice. The greatest PCE = 5.75 % was achieved for the solar cell assembled using TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoanode indicating 47.81 % improved performance relative to that of the reference DSSC containing TiO2 + 5 wt% ZnFe2O4 photoelectrode. The electrochemical impedance spectra (EIS) approved that the DSSC with the TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoelectrode nanomaterial had the lowest charge transfer resistance but the greatest e-h recombination resistance at the interfaces of photoanode/dye/electrolyte. Hence, it had the quickest electron transport rate, and the greatest electron collecting efficiency in addition to the highest dye loading capacity and least photoluminescence (PL) intensity (charge recombination) which were all prominently beneficial for improvement of the DSSC performance.

Comparison effect of thin microrod‐nanowhisker manganese oxide (MnO2) and spherical grain‐like cobalt oxide (Co3O4) as nanofiller for performance‐enhanced composite gel terpolymer electrolyte‐based dye‐sensitized solar cells

AbstractGel polymer electrolyte (GPE) are better replacement of liquid electrolyte for dye‐sensitized solar cell (DSSC) but they have low efficiency due to insufficient segmental motion within the electrolyte. By incorporating transition metal oxide nanofiller, it can improve the performance of DSSC due to the existence of cross‐linking center that provides interaction with polymer side chain and redox mediator. Two different transition metal oxides (namely, manganese oxide, MnO2 and cobalt oxide, Co3O4) were synthesized using sonochemical method and incorporated as nanofiller. Poly (vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) (P(VB‐co‐VA‐co‐VAc)) as a host terpolymer and sodium iodide (NaI) as a dopant salt were used to formulate the composite gel terpolymer electrolytes (CGPEs). The two different shapes of nanofiller have impacted the performance of CGPE proven by the structural analysis. It was found that both systems, the highest ionic conductivity achieved at 2.5 wt% of MnO2 and Co3O4 content with values of 6.40 and 5.2 mS cm−1, respectively. Surprisingly, the performance DSSC of Co3O4‐based CGPE was higher due to the strong Lewis's acidity of Co3O4, which absorb more iodide ions into the surface and facilitating the ions mobility. CGPE containing 2.5 wt% Co3O4 yield the highest efficiency, with value of 3.69%.

MITRAGYNA SPECIOSA DYE SENSITISER AS THE LIGHT-HARVESTING MOLECULES FOR DYE-SENSITISED SOLAR CELLS

In this study, natural dye sensitisers derived from ketum (Mitragyna speciosa-MS), spinach (Spinacia oleracea-SO), curry (Murraya koenigii-MK), papaya (Carica papaya-CP), and henna (Lawsonia inermis-LI) were investigated for dye-sensitised solar cells (DSSCs). Ultraviolet-Visible Spectroscopy (UV-Vis), Fourier Transform Infrared spectroscopy (FTIR), Open-Circuit Voltage Decay (OCVD) and Current to Voltage (I-V) were used to analyse the natural dye and the fabricated DSSC. It was observed that all dye solutions contain the majority of important functional groups of chlorophyll-based sensitisers, which is crucial for the dye-to-TiO2 (Titanium (II) Oxide) attachment, making them suitable sources of energy harvesting pigments. In this regard, the dye pH and chemical bonding of the respective dyes play a significant role that contribute to the overall performance of the DSSCs. It was discovered that a dye based on MK provided the best DSSC performance. This is because MK-based dye has higher content of functional groups, an optimal pH, and the slowest properties of back electron recombination among the OCVD measurements. Because of the combination of these properties, the open-circuit voltage (VOC), short-circuit current density (JSC), and power conversion efficiency (PCE) values have been determined to be 0.58 V, 2.48 mA/cm2, and 0.47%, respectively.

Synthesis of titanium dioxide/reduced graphene oxide nanocomposite by ultrasound-assisted mechanical mixing method for fabricating photoanode to upgrade the performance and stability of dye-sensitized solar cell

• TiO 2 /rGO was successfully synthesized by ultrasound-asissted mechanical mixing method. • 1.0 wt.% rGO under 720-W ultrasonic power was optimal synthesis conditions. • The presence of rGO enhanced and stabilized DSSC performance. • Nano-sized TiO 2 paticles were evenly anchored on rGO sheets. • rGO could enhance the thermostability and photostability of the DSSC. Herein, titanium dioxide/reduced graphene oxide (TiO 2 /rGO – TG) nanocomposite was synthesized via the ultrasound-assisted mechanical mixing method, used for the fabrication of photoanode in dye-sensitized solar cells (DSSCs). The DSSCs performance was evaluated by current density-voltage (J-V) curves and electrochemical impedance spectroscopy (EIS), showing that the sample with 1.0 wt.% rGO under the ultrasonic power of 720 W, was an optimal material for fabricating photoanode in DSSCs, which obtained the power conversion efficiency of 6.37 %. Additionally, in the 500-hour illumination test under 300-watt metal-halide lamp and the 100-hour drying at 85 °C, DSSCs with the presence of rGO proved better stability in comparison with DSSCs fabricated from commercial TiO 2 . The characterization of TG was analyzed by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, indicating that TiO 2 nanoparticles are uniformly distributed onto the rGO sheets with the average diameter from 20 to 70 nm.

The preparation of ZnO-based dye-sensitized solar cells usingRhus,LinariaandPunica

This paper focuses on fabricating zinc oxide (ZnO)-based dye-sensitized solar cells (DSSCs) utilizing three types of dyes derived from Rhus, Linaria and Punica flowers. The zinc oxide thin films were prepared on tin-doped indium oxide-coated glass substrates at 70°C according to the successive ionic layer adsorption and reaction method. Organic sensitizers were extracted from Rhus, Linaria and Punica flowers using the solvent ethanol. The fabricated solar cells were characterized by using the X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), ultraviolet–visible spectroscopy and Fourier transformation infrared spectroscopy techniques. The maximum photovoltaic values were obtained from the zinc oxide/Linaria-based DSSC, which exhibits a current density (Jsc) of 0.328 mA/cm–2, an open-circuit voltage (Voc) of 1 V, a fill factor of 64% and an energy conversion efficiency (η) of 0.210%, despite being the thinnest, at 1.381 μm, among all the DSSCs studied in this work. EDS analysis indicated that the weight contribution of oxygen for the Linaria DSSC is 53.30%, and this value is higher than those for Rhus and Punica DSSCs. The results suggest that the Linaria dye sensitizer can be a good candidate for minimizing the thickness of photoelectrode films and improving the performance of DSSCs.

Study of Single Diode Model of DSSC Based on Reduced Graphene Oxide as Counter Electrode

We studied the characteristic of reduced graphene oxide (RGO) as a counter electrode (CE) in Pt-free dye-sensitized solar cell (DSSC) using single diode model equation based on current density-voltage (J-V) measurement. The electrical characteristics of DSSC was investigated by electrochemical impedance spectroscopy (EIS) in order to knowing the catalytic properties of RGO as counter electrode. The RGO thin film as CE was deposited on fluorine-doped tin oxide (FTO) substrate and stacked with FTO/TiO2/ruthenium dye/mosalyte/RGO/FTO DSSC structure. The RGO film was obtained from GO (graphene oxide) film that was thermally reduced at 200°C for one hour under argon flow. The performance of DSSC with RGO as CE was characterized by current-voltage measurement and the interface between each layer was observed by Electrochemical Impedance Spectroscopy (EIS). The device efficiency (η) of DSSC that used GO and RGO film as CE are 0.09% and 3.43%, respectively. DSSC parameters such as series resistance (RS) shunt resistance (RSH), and ideality factor (n) were obtained from J-V curve which analyzed using single diode model equation. All samples have a Rs value of 2 indicates that all devices have a good ohmic contact. The RSH of device using RGO-1mg/ml is increase (from 2850 to 3670 Ω.cm2) compared with GO indicate that thermal reduction is successes. The RGO film shows a comparable performance to Pt-conventional CE thus it is a good candidate as alternative of DSSC counter electrode.

Analytical Methods for Mathematical Modeling of Dye-Sensitized Solar Cells (DSSCs) Performance for Different Local Natural Dye Photosensitizers

In this paper, a new approach to generate the modified ideal diode factor of solar cells was developed which overcomes the problem of assuming its value a constant. Five models were employed to calculate the five-model parameters of one standard solar cell and fourteen DSSCs with varying photosensitizers. The results exhibit the conversion efficiencies of the solar cells studied lies in the range 2.57% ≤ η ≤ 0.03%. In particular, the standard cell has the highest efficiency 3.02% followed by DSSCs with photosensitizers: bitter gourd (2.57%), mango (1%), and bougainvillea (0.83%). Also, the five model parameters calculated are all positive for El Tayyan model and the rest of the models show discrepancies of varying degrees. Furthermore, despite the existence of these discrepancies, the results reveal good fit between the model data and experimental data I-V curves. This suggests the tendency or possibility that irregular parameters may be desirable for some applications. Thus, the discrepancies found in the estimated parameters can serve as a vital assessment criterion and tool for researchers and engineers in selecting the appropriate parameter estimation method for their applications. Keywords: Analytical methods, Mathematical modeling, DSSCs, Photosensitizers, Irregular parameters, Conversion efficiency.

The Effects of Pt-Doped TiO2 Nanoparticles and Thickness of Semiconducting Layers at Photoanode in the Improved Performance of Dye-Sensitized Solar Cells.

This work synthesized Pt-doped dye-sensitized solar cells (DSSC) with different molar ratios and thicknesses. The materials were revealed fully through X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photovoltaic properties of the sample were studied by UV-visible spectroscopy, electrochemical impedance spectroscopy (EIS), and IPEC (incident photon-to-current conversion efficiency) techniques. EIS analysis established the decrease in series resistance at the electrolyte interface. It could be one of the reasons for the increase in electron transfer rate and decrease in the recombination process at the interface. Statistical data obtained from optical and electrical investigations revealed that the electrical power-output efficiency of DSSC was 14.25%. It was found that a high ratio of Pt doping and thinner thickness can promote cell performance, owing to the reduction of series resistance, lower bandgap, and high dye adsorption. Doping TiO2 with Pt reduced its energy bandgap and introduces intermediate energy levels inside TiO2 to facilitate the transition of electrons at low excitation energies. The absorbance of the samples 0.15 M Pt and 0.25 M Pt showed improvement in the wavelength ranging from 200 to 800 nm by Pt doping.

Synergistically improved photovoltaic performances of dye-sensitized solar cells with metal-free organic cosensitizer and hybrid rGO-TiO2 photoanode

The photovoltaic performances of the dye-sensitized solar cells were considerably improved via comprising the device structure with the metal-free organic dye cosensitizer and the hybrid photoanode. The cosensitizer was composed of Eosin Y and Coumarin (EY-CM) dyes, and the hybrid photoanode was constructed with the reduced graphene oxide-anchored titanium dioxide (rGO-TiO2) nanocomposites. Due to the aggregation of highly conductive rGO with semiconductive TiO2, the nanocomposites exhibited the decreased interfacial resistance; hence, the electron transport could be improved in the solid-state medium of the photoanode. Meanwhile, the cosensitization of EY-CM dyes could give rise to the increased photon absorbance at the wide spectral range; and their energy level alignment with rGO-TiO2 could lead to the enhanced hopping conduction of the photo-generated electrons. Furthermore, the configuration of rGO-TiO2/EY-CM allowed us to increase the electron injection lifetime, which could reduce the photocarrier recombination at the photoanode/sensitizer interface. Owing to the synergetic effects from both the rGO-TiO2 hybrid photoanode and the EY-CM cosensitizer, the fabricated dye-sensitized solar cell eventually showed the increased power conversion efficiency up to ∼6.14% under 1-Sun illumination with 100 mW/cm2.

Efisiensi Counter Electrode Dengan Pengurangan Pemakaian Platina Menggunakan Komposit Bahan Ramah Lingkungan Grafin Dan Carbon Nanotubes Untuk Aplikasi Dye Sensitized Solar Cells

<p><span lang="EN-AU">Dye sensitized solar cells (DSSCs) are the most popular solar cells in the third generation. DSSCs have been widely developed as an alternative to silicon-based solar cells because of its easy manufacturing process, high efficiency, easy production costs, and environmental friendliness. Graphene and carbon nanotubes (CNTs) are promising materials to reduce the use of platinum (Pt) in counter electrode (CE) due to their excellent properties, such as thermal, electrical conductivity, and high surface area. One of the derivatives of graphene that is often used is reduced graphene oxide (rGO) which is produced from GO solution by a reduction process. GO was synthesized in an electrolyte containing surfactant by the electrochemical exfoliation method. The specially prepared sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-silphonate (TC14) surfactant was used in GO synthesis. The CE thin film of TC14-rGO/CNTs/Pt hybrid shows the highest efficiency values (0.0594%) with Jsc, Voc, and FF of 0.176 mA/cm2, 0.622 V, and 0.464, respectively. This was believed due to the conjugated network in CNTs acts as a connecting cable between the TC14-rGO layers and as a vacancy filler, the high electrical conductivity value and the larger surface area also cause faster electron movement, making these properties important in DSSC performance. The FF value which is also the highest in the TC14-rGO/CNTs/Pt hybrid samples as CE is also influenced by its structure. The high surface area of CNTs and TC14-rGO in the TC14-rGO/CNTs/Pt hybrid samples exhibited important properties for generating dye after electron injection and led to a faster route of electron regulation during DSSCs processing. These findings indicate that Pt composited with environmentally friendly and inexpensive materials such as T14-rGO and CNTs can improve CE performance in DSSCs applications. Based on this, this research can be used as a basis for further research on the fabrication of carbon-based CE</span></p>

Effect of dye complex structure on performance in DSSCs; An experimental and theoretical study

Use of cobalt-complexes as dye in dye sensitized solar cells (DSSCs) has been a viable contender in the field of photovoltaics due to their low cost, easy production, and wide availability of sources. In this study, we investigated the effect of succinic acid (suc), 1,10-phenanthroline (phen), and benzene-1,3,5-tricarboxylate (BTC) as ligand in metals complex sensitizers with these general formulas: (1) [Co(suc)]n, (2) [Co2(suc)2(phen)2], (3) [Co3(BTC)2(H2O)n]n, and (4) [Co(HBTC) (phen) (H2O)2]; for DSSCs. The bandgap, and energy levels have an important role in photoelectron emission during photovoltaic processes. The bandgap, and energy levels of these dyes (1–4) were estimated by Ultraviolet-Visible (UV-Vis), spectroscopies, and cyclic voltammetry (CV).Delocalized π-electron of phenanthroline in two compounds (2, 4) by effectively reducing band gap energies leads to power conversion efficiency (PCE) of 0.511%, and 1.006%, respectively. Their PCEs to compounds (1, 3) showed an approximate increase of 60%, and 31%, respectively. Furthermore, BTC ligands by more coordinated carboxylate groups in contrast with succinic molecules due to binding sites with TiO2 cause further enhancement in the efficiency for compounds (3, 4) in contrast with compounds (1, 2). Reasonable agreement is found between experimental and theoretical values calculated using density functional theory (DFT) for the bandgaps and energy levels.

Polynary metal selenide CoSe2/NiSe2/MoSe2 porous nanospheres as efficient electrocatalytic materials for high-efficiency dye-sensitized solar cells

• CoSe 2 /NiSe 2 /MoSe 2 porous nanosphere was synthesized. • CoSe 2 /NiSe 2 /MoSe 2 had abundant active sites and excellently catalytic activities. • The PCE of CoSe 2 /NiSe 2 /MoSe 2 (9.49%) was higher than that of Pt (8.28%). Transition metal selenides with porous structure have a brightly prospects due to their low cost, large surface area, high catalytic efficiency, and facile synthetic method comparing with Pt-based electrocatalytic materials in power transformation systems. Herein, we have successfully prepared porous structure transition metal selenide CoSe 2 /NiSe 2 /MoSe 2 nanospheres through simple solvothermal method and stepwise selenization process from glycerol precursor nanospheres. Uniform selenide nanoparticles were formed on the surface of the porous nanospheres. The resultant CoSe 2 /NiSe 2 /MoSe 2 porous nanospheres not only provided more redox pairs, but also had better electron transfer performance and shorter charge transfer distance between the electrolyte and the electrode materials, accelerating the charge transfer process. Therefore, CoSe 2 /NiSe 2 /MoSe 2 nanospheres delivered excellent electrochemical performance in dye-sensitized solar cells which achieved an excellent power conversion efficiency of 9.49% comparing to the cell based on Pt (8.28%). This work can offer a new vision on the design of high-performance, environment-friendly, and Pt-free electrocatalysts for solar cells.

Improving photovoltaic performance of dye-sensitized solar cells by doping SnO2 compact layer with potassium

• K-doped SnO 2 film is fabricated by spin-coating technique. • The electrical properties of SnO 2 film are improved by introducing potassium. • The recombination effect between FTO and electrolyte is effectively suppressed. • The champion PCE of devices is improved from 7.02% to 7.84%. SnO 2 film doped with potassium has been fabricated by spin-coating technique on fluorine-doped tin oxide (FTO) glass. The electrical properties of the SnO 2 film are improved by introducing potassium, which is in favor of electrons transfer from TiO 2 film to FTO glass. Meanwhile, the K-doped SnO 2 compact layer is beneficial in suppressing the recombination effect between the FTO glass and the electrolyte. As a result, the short-circuit current density of dye-sensitized solar cells (DSSCs) is enhanced from 15.20 mA cm −2 to 17.48 mA cm −2 . Then, the highest power conversion efficiency is 7.84 % for the optimized DSSC based on the K-doped SnO 2 /TiO 2 film, which is larger than those of the DSSCs based on TiO 2 film (7.02 %) and non-doped SnO 2 /TiO 2 film (7.18 %).