Bifacial Dye-sensitized Solar Cells Research Articles

Transparent Metal Selenide Alloy Counter Electrodes for High‐Efficiency Bifacial Dye‐Sensitized Solar Cells

AbstractThe exploration of cost‐effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye‐sensitized solar cells (DSSCs). Transparent counter electrodes based on binary‐alloy metal selenides (M‐Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution‐based method and employed in efficient bifacial DSSCs. Owing to superior charge‐transfer ability for the I−/I3− redox couple, electrocatalytic activity toward I3− reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85Se, 7.85 % and 4.37 % for Ni0.85Se, 6.43 % and 4.24 % for Cu0.50Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels.

Cost-effective bifacial dye-sensitized solar cells with transparent iron selenide counter electrodes. An avenue of enhancing rear-side electricity generation capability

Alloy materials have established themselves as alternative electrocatalysts for electrochemical devices because of their cost-effectiveness, high conductivity, good electrocatalytic activity, and reasonable stability. Aiming at reducing fabrication cost without sacrificing power conversion efficiency of dye-sensitized solar cells (DSSCs), we report the feasibility of designing transparent and cost-effective Fe–Se alloy counter electrodes for bifacial DSSCs. Due to the rapid charge transfer ability and electrocatalytic activity, maximum front and rear efficiencies of 7.64% and 4.95% are measured for the DSSC with FeSe alloy electrode in comparison with 6.97% and 3.56% from Pt-based solar cell. The impressive results along with simple synthesis highlight the potential application of Fe–Se alloys in robust bifacial DSSCs.

Bifacial dye-sensitized solar cells with enhanced rear efficiency and power output.

Pursuing a high power conversion efficiency with no sacrifice of cost-effectiveness has been a persistent objective for dye-sensitized solar cells (DSSCs). One promising solution to this impasse is increased light harvesting. Previous efforts in light harvesting have been made on setting blocking layers or reflecting layers, or adding a light harvester, resulting in tedious procedures without reducing the expenses. We present a mild solution strategy for synthesizing transparent Ru-Se alloy counter electrodes (CEs) for bifacial DSSC applications, displaying optimal front and rear efficiencies of 8.76% and 5.90%, respectively. In comparison with pristine Pt-based solar cells, the maximum power output has also been markedly enhanced. Moreover, fast start-up, high multiple start capability, and good stability are observed in the bifacial DSSCs with transparent Ru-Se binary alloy electrodes. The impressive efficiencies along with simple preparation of the cost-effective Ru-Se alloy CEs demonstrates their potential application in robust DSSCs.

Transparent nickel selenide alloy counter electrodes for bifacial dye-sensitized solar cells exceeding 10% efficiency.

In the current work, we report a series of bifacial dye-sensitized solar cells (DSSCs) that provide power conversion efficiencies of more than 10% from bifacial irradiation. The device comprises an N719-sensitized TiO2 anode, a transparent nickel selenide (Ni-Se) alloy counter electrode (CE), and liquid electrolyte containing I(-)/I3(-) redox couples. Because of the high optical transparency, electron conduction ability, electrocatalytic activity of Ni-Se CEs, as well as dye illumination, electron excitation and power conversion efficiency have been remarkably enhanced. Results indicate that incident light from a transparent CE has a compensation effect to the light from the anode. The impressive efficiency along with simple preparation of the cost-effective Ni-Se alloy CEs highlights the potential application of bifacial illumination technique in robust DSSCs.

Highly transparent and efficient counter electrode using SiO2/PEDOT-PSS composite for bifacial dye-sensitized solar cells.

A highly transparent and efficient counter electrode was facilely fabricated using SiO2/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) inorganic/organic composite and used in bifacial dye-sensitized solar cells (DSCs). The optical properties of SiO2/PEDOT-PSS electrode can be tailored by the blending amount of SiO2 and film thickness, and the incorporation of SiO2 in PEDOT-PSS provides better transmission in the long wavelength range. Meanwhile, the SiO2/PEDOT-PSS counter electrode shows a better electrochemical catalytic activity than PEDOT-PSS electrode for triiodide reduction, and the role of SiO2 in the catalytic process is investigated. The bifacial DSC with SiO2/PEDOT-PSS counter electrode achieves a high power conversion efficiency (PCE) of 4.61% under rear-side irradiation, which is about 83% of that obtained under front-side irradiation. Furthermore, the PCE of bifacial DSC can be significantly increased by adding a reflector to achieve bifacial irradiation, which is 39% higher than that under conventional front-side irradiation.

Thickness-self-controlled synthesis of porous transparent polyaniline-reduced graphene oxide composites towards advanced bifacial dye-sensitized solar cells

A powerful synthesis strategy is proposed for fabricating porous polyaniline-reduced graphene oxide (PANI-RGO) composites with transparency up to 80% and thickness from 300 to 1000 nm for the counter electrode (CE) of bifacial dye-sensitizing solar cells (DSSCs). The first step is to combine the in-situ positive charge transformation of graphene oxide (GO) through aniline (ANI) prepolymerization and the electrostatic adsorption of ANI oligomer-GO to effectively control the thickness of ultrathin PANI-GO films by adjusting pH of the polymerization media. In the second step, PANI-GO films are reduced with hydroiodic acid to simultaneously enhance the apparent redox activity for the I3−/I− couple and their electronic conductivity. Incorporating the RGO increases the transparency of PANI and facilitates the light-harvesting from the rear side. A DSSC assembled with such a transparent PANI-RGO CE exhibits an excellent efficiency of 7.84%, comparable to 8.19% for a semi-transparent Pt-based DSSC. The high light-harvesting ability of PANI-RGO enhances the efficiency retention between rear- and front-illumination modes to 76.7%, compared with 69.1% for a PANI-based DSSC. The higher retention reduces the power-to-weight ratio and the total cost of bifacial DSSCs, which is also promising in other applications, such as windows, power generators, and panel screens.

Bifacial dye-sensitized solar cells: A strategy to enhance overall efficiency based on transparent polyaniline electrode

Dye-sensitized solar cell (DSSC) is a promising solution to global energy and environmental problems because of its clean, low-cost, high efficiency, good durability, and easy fabrication. However, enhancing the efficiency of the DSSC still is an important issue. Here we devise a bifacial DSSC based on a transparent polyaniline (PANI) counter electrode (CE). Owing to the sunlight irradiation simultaneously from the front and the rear sides, more dye molecules are excited and more carriers are generated, which results in the enhancement of short-circuit current density and therefore overall conversion efficiency. The photoelectric properties of PANI can be improved by modifying with 4-aminothiophenol (4-ATP). The bifacial DSSC with 4-ATP/PANI CE achieves a light-to-electric energy conversion efficiency of 8.35%, which is increased by ~24.6% compared to the DSSC irradiated from the front only. This new concept along with promising results provides a new approach for enhancing the photovoltaic performances of solar cells.

Pt-free transparent counter electrodes for cost-effective bifacial dye-sensitized solar cells

In this feature article, we pay special attention to the recent advances in the development of Pt-free transparent CEs and highlight their applications in bifacial DSCs.

Highly Transparent Carbon Counter Electrode Prepared via an in Situ Carbonization Method for Bifacial Dye-Sensitized Solar Cells

A facile in situ carbonization method was demonstrated to prepare the highly transparent carbon counter electrode (CE) with good mechanical stability for bifacial dye-sensitized solar cells (DSCs). The optical and electrochemical properties of carbon CEs were dramatically affected by the composition and concentration of the precursor. The well-optimized carbon CE exhibited high transparency and sufficient catalytic activity for I3(-) reduction. The bifacial DSC with obtained carbon CE achieved a high power conversion efficiency (PCE) of 5.04% under rear-side illumination, which approaches 85% that of front-side illumination (6.07%). Moreover, the device shows excellent stability as confirmed by the aging test. These promising results reveal the enormous potential of this transparent carbon CE in scaling up and commercialization of low cost and effective bifacial DSCs.

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.

A transparent and stable polypyrrole counter electrode for dye-sensitized solar cell

A novel transparent and stable polypyrrole (PPy) electrode that can properly serve as a counter electrode for the bifacial dye-sensitized solar cell (DSSC) has been prepared by in situ polymerization of pyrrole monomer on FTO glass. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurement show the considerable catalytic activity of PPy counter electrode. The photovoltaic parameters of bifacial DSSCs are strongly dependent on the initial monomer concentration of pyrrole. The optimized PPy counter electrode has been fabricated under the initial monomer concentration of 0.3 M, a bifacial DSSC based on this PPy electrode shows conversion efficiencies of 5.74% and 3.06% corresponding to front- and rear-side illumination, respectively. Compared to the conventional Pt-based DSSCs, the design of bifacial DSSC with transparent PPy counter electrode improves the utilization ratio of incident light. Moreover, the considerable conversion efficiency and the good long-term stability of PPy-based device demonstrated by the stability test highlight the potential large-scale commercial application of this transparent PPy counter electrode.

The application of camphorsulfonic acid doped polyaniline films prepared on TCO-free glass for counter electrode of bifacial dye-sensitized solar cells

Abstract In this paper, we assembled a low-cost and bifacial dye-sensitized solar cell with an optically transparent TCO (transparent conducting oxide)-free counter electrode using camphorsulfonic acid-doped polyaniline coated on normal glass. This polymer counter electrode was fabricated by spin coating on a TCO-free glass substrate followed by optimizing process of film thickness and thermal treatment. Because the camphorsulfonic acid doped polyaniline film had the high conductivity and the superior electrocatalytic activity, it could successfully act as a counter electrode that performs a dual role, transporting electrons from the electrode to an external circuit and reducing the redox couple in electrolyte. The superior photovoltaic performances with camphorsulfonic acid-doped polyaniline film, 84% from front illumination and 93% from rear illumination of conventional dye-sensitized solar cell using Pt and TCO glass, was exhibited. Because the complementary absorption properties with dye and electrochromic properties of PANI/CSA film had the advantage of light absorption from rear side illumination, this optically transparent polymer film was particularly used as an effective Pt and TCO-free counter electrode for bifacial dye-sensitized solar cell.

Design of an organic redox mediator and optimization of an organic counter electrode for efficient transparent bifacial dye-sensitized solar cells

A new thiolate/disulfide mediator was designed and synthesized by employing DFT calculations as a guide. It possesses high transparency to visible light, a very attractive feature for bifacially active transparent DSCs that require a highly transparent counter electrode (CE). Compared to the reported and most promising thiolate/disulfide mediator T(-)/T(2), this new analogous mediator produced a major enhancement in open circuit potential (V(OC)) by about 40 mV and correspondingly a higher power conversion efficiency (η) for DSCs. Furthermore, a highly uniform and transparent (transmittance > 91%) poly(3,4-ethylenedioxythiophene) (PEDOT(BE)) CE was prepared and could efficiently catalyze the reduction of the disulfide. Based on the novel transparent redox couple and PEDOT(BE) CE, a new type of iodine-free and Pt-free transparent bifacial DSC was successfully fabricated. This new bifacial device could not only yield a promising front-illuminated η of 6.07%, but also produce an attractive η as high as 4.35% for rear-side irradiation, which exceeds the rear-illuminated η of 3.93% achieved for the same type of device, employing the dark-colored I(-)/I(3)(-) electrolyte.

In Situ Prepared Transparent Polyaniline Electrode and Its Application in Bifacial Dye-Sensitized Solar Cells

Highly uniform and transparent polyaniline (PANI) electrodes that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) were prepared by a facile in situ polymerization method. They were used to fabricate a novel bifacially active transparent DSSC, which showed conversion efficiencies of 6.54 and 4.26% corresponding to front- and rear-side illumination, respectively. Meanwhile, the efficiency of the same photoanode employing a Pt counter electrode was 6.69%. Compared to conventional Pt-based DSSCs, the design of the bifacial DSSC fabricated in this work would help to bring down the cost of energy production due to the lower cost of the materials and the higher power-generating efficiency of such devices for their capabilities of utilizing the light from both sides. These promising results highlight the potential application of PANI in cost-effective, transparent DSSCs.

Bifacial dye-sensitized solar cells based on vertically orientedTiO2 nanotube arrays

In this work we describe a novel bifacial design concept for dye-sensitized solar cells(DSCs). Bifacial DSCs are fabricated with ruthenium complex chemisorbed double-sidedTiO2 nanotube arrays on a Ti metal substrate, in combination with two electron-collectingcounter electrodes. Our investigation shows that the present bifacial DSCs have similarconversion efficiencies when illuminated from either their front or rear side, and asummated output power when illuminated on both sides. Furthermore, this type of bifacialDSC is also able to summate the output power of each side when working at an‘unsymmetrical’ mode, in which much different output powers are generated by the frontand rear sides. Therefore, this bifacial design concept exhibits a promising potential toreduce the cost of solar electricity when DSCs are operated at a location where a highalbedo radiation is available.

The two sides of solar energy

A bifacial dye-sensitized solar cell that can efficiently generate electricity when illuminated from either side may help bring down the cost of solar energy production.

Bifacial dye-sensitized solar cells based on an ionic liquid electrolyte

Solar energy is a promising solution to global energy-related problems because it is clean, inexhaustible and readily available. However, the deployment of conventional photovoltaic cells based on silicon is still limited by cost, so alternative, more cost-effective approaches are sought. Here we report a bifacial dye-sensitized solar cell structure that provides high photo-energy conversion efficiency (∼6%) for incident light striking its front or rear surfaces. The design comprises a highly stable ruthenium dye (Z907Na) in combination with an ionic-liquid electrolyte and a porous TiO2 layer. The inclusion of a SiO2 layer between the electrodes to prevent generation of unwanted back current and optimization of the thickness of the TiO2 layer are responsible for the enhanced performance. Low-cost, efficient solar cells are sought as an alternative to silicon photovoltaics. Here a dye-based bifacial solar cell that is capable of efficient generation of electricity for light incident on either its front or rear face is demonstrated.

05/01231 Energy savings of office buildings by the use of semi-transparent solar cells for windows

Dye-sensitized solar cell (DSSC) is the most promising of third generation solar cells for large scale applications due its low cost, flexibility, and scalable manufacturability. However, enhancing the efficiency of the DSSC is still highly desired. In this study, we designed a novel bifacial DSSC based on a transparent Polyaniline (PANI) films as counter electrode (CE) associated with coral-like TiO2 nanostructured films, which can be used as the photoanode. PANI-based CEs were prepared by a facile in situ polymerization, while coral-like TiO2 films were chemically synthesized at low temperature through the sol–gel process. Owing to the light irradiation from both the front and the rear sides, it is expected that higher density of dye molecules should be excited. In addition, due to the excellent light scattering of the coal-like TiO2 and high specific surface area of PANI nanofibers (NFs), more carriers are generated. Both these factors resulted in the increase of the conversion efficiency. The bifacial DSSC fabricated by combining the PANI NFs-based film and the coral-like TiO2 film in the presence of the expensive N719 dye molecules showed the efficiency of 8.22% corresponding to the both-side irradiation. In comparison, similar cells employing either a cross-linked PANI- or Pt-based CE showed efficiencies of 7.81% and 7.75%, respectively. The results of the similar cells in the presence of the low cost CoPC dye molecules showed efficiencies of 0.29%, 0.22%, and 0.27%, for DSSCs comprised of PANI NFs-, cross-linked PANI-, and Pt-based CEs, respectively. The low fabrication cost as well as the improved light absorption highlights the potential application of the coral-like TiO2 and PANI NFs-based films in fabrication of bifacial DSSCs.