Bifacial Dye-sensitized Solar Cells Research Articles

Pt crystalline ultrathin films as counter electrodes for bifacial dye-sensitized solar cells

This study is to develop the Pt crystalline ultrathin films as high-transparent, efficient, and low-Pt-loaded counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSCs). The 1-nm-thick Pt ultrathin films are sputtered on fluorine-doped tin oxide substrates and thermal annealed at 400 °C. After annealing, as-prepared amorphous-nanocrystal-mixed Pt films become high-crystalline films with better optical transmittance and electrocatalytic ability to I3− reduction for bifacial DSCs. The rear-to-front ratios of short-circuit current density and power conversion efficiency of DSCs with crystalline ultrathin Pt CEs are as high as 81 and 83%, respectively.

A Simple Cost-Effective Approach to Enhance Performance of Bifacial Dye-Sensitized Solar Cells

A simple cost-effective approach was demonstrated to increase the rear efficiency and ratio of rear-to-front efficiencies for bifacial dye-sensitized solar cells (DSCs). This was achieved by enhancing the transparency of the counter electrode of the DSC using a composite of platinum- and aluminum-doped zinc oxide (Pt/AZO). The thermally deposited composite Pt/AZO counter electrodes exhibited transmittance T550 nm = 0.70–0.74 versus Pt with 0.63. The comparable front power conversion efficiency (PCEfront) of fabricated DSCs using the composite Pt/AZO counter electrodes suggested that the presence of AZO in the composite had minimal effect on the catalytic activity of the platinum. DSCs with composite Pt/AZO counter electrode presented superior rear PCEs compared with platinum counterparts and was attributed to higher short-circuit current density $J_{{\rm sc}}$ resulting from the larger transmittance of the composite counter electrode. The higher PCErear / PCEfront of the composite-based DSCs compared with Pt-based DSC suggested that such transparent composite counter electrodes could be employed in bifacial DSCs.

Bifacial quasi-solid-state dye-sensitized solar cells with Poly (vinyl pyrrolidone)/polyaniline transparent counter electrode

We synthesized Poly (vinyl pyrrolidone) (PVP)/polyaniline (PANI) nanocomposites and applied them as transparent counter electrode (CE) for bifacial quasi-solid-state dye-sensitized solar cells (DSSCs). PVP surrounded with aniline acted as efficient steric stabilizer in the polymerization process. Moreover, the present of PVP in PANI CE facilitated the generation of active reaction-sites in the interface between counter electrode and electrolyte and further reduced the electron recombination. The DSSC fabricated with PVP (4wt%)/PANI CE exhibited improved power conversion efficiency up to 5.45%, which was comparable to that of DSSC assembled with Pt CE (5.57%). In the case of rear-illumination, the PVP (4wt%)/PANI based DSSC showed an efficiency of 4.66%, which was 85.5% of the efficiency obtained from front illumination and much higher than that of DSSC with Pt CE (1.14%). The bifacial DSSC with PVP/PANI counter electrode showed an optimal power efficiency of 5.81% under illumination from both front and rear sides, which is higher than that of Pt based DSSC (5.70%) under the same condition. Long-term stability tests indicated that the photovoltaic device with PVP/PANI counter electrode exhibited an enhanced durability than that of DSSC assembled with Pt CE.

Highly transparent metal selenide counter electrodes for bifacial dye-sensitized solar cells

Creation of transparent counter electrode (CE) electrocatalysts for bifacial dye-sensitized solar cells (DSSCs) is a persistent objective for reducing cost of photovoltaic conversion. We present here the experimental realization of highly transparent CuSe CEs by a mild solution method for liquid-junction bifacial DSSCs. The resultant CuSe CEs show superior electrocatalytic activity toward I3− reduction reaction. By optimizing the pH values in synthesizing CuSe electrodes, the maximal front efficiency of 6.21% and rear efficiency of 4.72% are recorded on the corresponding bifacial DSSC. Both catalytic activity and photovoltaic performances can be further elevated by alloying CuSe with Co or Fe, yielding promising efficiencies of 7.81% and 5.38% under front and rear irradiations, respectively.

Efficient bifacial dye-sensitized solar cells through disorder by design.

Herein we realize an optical design that optimizes the performance of bifacial solar cells without modifying any of the usually employed components. In order to do so, dielectric scatterers of controlled size and shape have been successfully integrated in the working electrodes of dye-sensitized solar cells (DSSCs), resulting in bifacial devices of outstanding performance. Power conversion efficiencies (PCEs) as high as 6.7% and 5.4% have been attained under front and rear illumination, respectively, which represent a 25% and a 33% PCE enhancement with respect to an 8 μm-thick standard solar cell electrode using platinum as the catalytic material. The remarkable bifacial character of our approach is demonstrated by the high rear/front efficiency ratio attained, around 80%, which is among the largest reported for this sort of device. The proposed optimized design is based on a Monte Carlo approach in which the multiple scattering of light within the cell is fully accounted for. We identified that the spherical shape of the scatterers is the key parameter controlling the angular distribution of the scattering, the most efficient devices being those in which the inclusions provide a narrow forward-oriented angular distribution of the scattered light.

Bifacial quasi-solid-state dye-sensitized solar cells with metal selenide counter electrodes

Bifacial dye-sensitized solar cell (DSSC) is a promising solution to reduce the cost of photovoltaic conversion. We present here the experimental realization of bifacial quasi-solid-state DSSC from a TiO2 photoanode, a semitransparent gel electrolyte, and a Ti grid supported metal selenide (MSe, M=Co, Ni, Ru) counter electrode (CE). In comparison with front efficiency of 4.87% and rear efficiency of 1.19% for Ti grid supported Pt based DSSC, the efficiencies are enhanced to 6.51% and 1.84% on the solar cell with cost-effective Ti grid supported RuSe CE. The preliminary results demonstrate that this architecture is promising in realizing cost-effective bifacial quasi-solid-state DSSCs without sacrificing photovoltaic performances.

Transparent counter electrode from palladium selenide for bifacial dye-sensitized solar cell

Aiming at reducing fabrication cost without sacrificing power conversion efficiency (PCE) of dye-sensitized solar cell (DSSC), transparent palladium selenide (Pd–Se) alloys are prepared by a cyclic voltammetric electrodeposition and utilized as counter electrodes (CEs) in bifacial DSSCs. The electrocatalytic activities of Pd–Se alloy CEs with adjustable stoichiometries are investigated, yielding an optimized alloy electrode at Pd7Se4. The PCE of the bifacial DSSC based on Pd7Se4 alloy CE shows front and rear efficiencies of 6.70% and 2.38% in comparison with 6.43% and 0.01% from pyrolytic platinum based solar cell, respectively. The results demonstrate that the Pd7Se4 alloy CE can serve as a good candidate for CE in DSSCs application.

In-situ fabricated transparent conducting nanofiber-shape polyaniline/coral-like TiO2 thin film: Application in bifacial dye-sensitized solar cells

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.

Counter electrodes from Mo–Se nanosheet alloys for bifacial dye-sensitized solar cells

Pursuit of cost-effective counter electrodes (CEs) with no sacrifice of photovoltaic performances is a persistent objective for dye-sensitized solar cells (DSSCs). We launch here the experimental realization of molybdenum selenide (Mo–Se) binary nanosheet CEs by a mild solution method. Due to high optical transparency, the bifacial DSSCs from cost-effective Mo–Se alloy CEs can realize electricity generation from either front or rear side. Particularly, the resultant Mo–Se alloy CEs show superior catalytic activity and charge-transfer ability toward I−/I3− redox electrolyte. The maximum front and rear efficiencies of 8.05% and 5.92% are recorded under simulated air mass 1.5 global irradiation, respectively. The impressive efficiency along with fast start-up, multiple start capability, and simple preparation highlights the potential application of the cost-effective and transparent Mo–Se alloy CE in robust bifacial DSSCs.

Nitrogen plasma modified CVD grown graphene as counter electrodes for bifacial dye-sensitized solar cells

In this study, we report modification of few-layer graphene grown by chemical vapour deposition via nitrogen plasma ion irradiation and its application as counter electrodes in bifacial dye-sensitized solar cells (DSSCs). The incorporation of nitrogen (N) atoms and defects are confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. Electrochemical impedance spectroscopy measurement reveals that the charge transfer resistance of graphene for triiodide reduction shows a decrease with increasing plasma treatment time, which is attributed to the increase of catalytic sites. The energy conversion efficiency of 3.12% is obtained when using the N-doped graphene films as counter electrodes, which is nearly 3 times higher than that of the pristine graphene films in DSSCs. More importantly, the DSSCs based on N-doped graphene CEs show much higher ηrear/ηfront ratio and better long-term stability than that based on Pt CEs. These results reveal the promising potential of this transparent N-doped graphene CEs in low cost and effective bifacial DSSCs.

Highly transparent ultrathin metal sulfide films as efficient counter electrodes for bifacial dye-sensitized solar cells

Highly transparent metal sulfides (Ni3S4, MoS2) are directly deposited on fluorine doped tin oxide (FTO) substrates as effective Pt-free counter electrodes (CEs) for novel bifacial dye-sensitized solar cells (DSSCs). The blocky-like Ni3S4 and petal-shaped MoS2 nanoparticles (NPs) possess large surface area, which provides amount of active site to contact with electrolyte. The films not only show high transmittance at visible wavelengths, but also exhibit prominent electrocataltytic activity and outstanding metallic conductivity in iodine/iodide based bifacial DSSCs. Under front-side irradiation (100mW/cm2), the bifacial DSSC based on the transparent Ni3S4 or MoS2 CE presents remarkable photovoltaic conversion efficiency (Eff=6.56%, 6.11%, respectively), closing to that of conventional Pt CE (Eff=6.83%). Moreover, by appending an ordinary mirror as a photo reflector to achieve both-side illumination, the bifacial DSSC using the transparent Ni3S4 or MoS2 sample as CE obtained higher short-circuit current density (Jsc) and more attractive power conversion efficiency (PCE) (Eff=7.06%, 6.65%, respectively). It indicates that the as-prepared transparent Ni3S4 and MoS2 CEs are promising potential candidates to explore low-cost and high-efficiency bifacial DSSCs.

In-situ Grown Hybrid Nanocarbon Composite for Dye Sensitized Solar Cells

Herein, a facile in-situ grown nanocarbon composite including one dimensional (1D) carbon nanotubes (CNTs) and two dimensional (2D) graphene nanosheets on FTO conductive glass substrates is used directly as a transparent counter electrode (CE) for dye sensitized solar cells (DSSCs) without any post-treatments. In the novel nano-composite, the CNTs without aggregations are not woven into each other, which is beneficial for the transport of carriers. Additionally, the 2D graphene between CNTs and the FTO conductive glass substrates is thought as the platform for accelerating the ballistic transport. It is found that the hybrid CNTs/graphene nano-composite exhibits relative high electrocatalytic activity for the reduction of triiodide. Besides, the design of bifacial DSSC with the hybrid transparent CNTs/graphene CE improves the utilization ratio of incident light. As a consequence, the bifacial DSSC with the optimized hybrid CNTs/graphene exhibits energy conversion efficiency (η) of 5.16% and 4.30%, corresponding to front- and rear-side illumination, respectively.

Transparent bifacial dye-sensitized solar cells based on an electrochemically polymerized organic counter electrode and an iodine-free polymer gel electrolyte

Bifacial transparent dye-sensitized solar cells (DSSCs) assembled with a highly transparent poly(3,4-ethylenedioxythiophene) (PEDOT) counter electrode (CE) and a non-absorptive iodine-free polymer gel electrolyte were developed. The PEDOT CEs were obtained via a facile in situ electrochemical polymerization method. Different charge capacities were applied in the polymerization process, and the PEDOT CEs were optimized with high transparency (>90 %) and favorable activity for catalyzing the reaction between the redox couples in the electrolyte. The gel electrolyte was prepared using an ionic liquid (1,2-dimethyl-3-propylinmidazolium iodide, DMPII) as the charge transfer intermediate and a polymer composite (PEO/PVDF-HFP) as the gelator without the addition of iodine. Besides high conductivity, the iodine-free electrolyte presented non-absorption in visible light region. The assembled bifacial DSSC device showed a power conversion efficiency (PCE) of 6.35 % under front-side irradiation, and 4.98 % under rear-side irradiation with intensity of 100 mW cm−2, which approached almost 80 % of that of the front-side irradiation. These promising results demonstrated the potential of these transparent organic CE and non-absorptive polymer gel electrolyte for further applications such as developing transparent bifacial photovoltaics.

Bifacial dye-sensitized solar cells with transparent cobalt selenide alloy counter electrodes

High power conversion efficiency and cost-effectiveness are two persistent objectives for dye-sensitized solar cell (DSSC). Electricity generation from either front or rear side of a bifacial DSSC has been considered as a facile avenue of bringing down the cost of solar-to-electric conversion. Therefore, the fabrication of a transparent counter electrode (CE) with a high electrocatalytic activity is a prerequisite to realize this goal. We present here the feasibility of utilizing transparent cobalt selenide (Co–Se) binary alloy counter electrode for bifacial DSSC application, in which binary Co–Se alloy electrode is synthesized by a mild solution strategy and the cell device is irradiated by either front or rear side. Due to the high optical transparency, charge-transfer ability, and electrocatalytic activity, maximum front and rear efficiencies of 8.30% and 4.63% are recorded under simulated air mass 1.5 (AM1.5) irradiation, respectively. The impressive efficiency along with fast start-up, multiple start capability, and simple preparation highlights the potential application of cost-effective and transparent Co–Se alloy CE in robust bifacial DSSCs.

Cost-effective, transparent iron selenide nanoporous alloy counter electrode for bifacial dye-sensitized solar cell

Pursuit of cost-effective and efficient counter electrodes (CEs) is a persistent objective for dye-sensitized solar cells (DSSCs). We present here the design of transparent Fe–Se nanoporous alloy CEs for bifacial DSSC applications. Due to the superior charge-transfer ability for I−/I3− redox couples, electrocatalytic reduction toward I3− species, and optical transparency in visible-light region, the bifacial DSSC with FeSe alloy electrode yields maximum front and rear efficiencies of 9.16% and 5.38%, respectively. A fast start-up, high multiple start capability, and good stability of the FeSe alloy CE demonstrate the potential applications in driving solar panels. The impressive efficiency along with simple preparation of the cost-effective Fe–Se nanoporous alloy CEs highlights their potential application in robust bifacial DSSCs.

Heteroatom-doped graphene-like carbon films prepared by chemical vapour deposition for bifacial dye-sensitized solar cells

Bifacial dye-sensitized solar cells (DSSCs) with the ability to utilize incidental light from both front- and rear-sides have drawn massive attention from researchers in recent years. Herein, nitrogen (N)-doped, sulphur (S)-doped and nitrogen/sulphur dual-doped transparent graphene-like carbon films (GFs) were synthesized by chemical vapour deposition (CVD) and confirmed by transmission electron microscopy (TEM), UV–Vis transmitted spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The doped GFs show good performance as counter electrodes (CEs) for fabrication of bifacial DSSCs. The bifacial DSSCs with high transparent N-doped, S-doped and N/S dual-doped GFs as CEs exhibit dramatically enhanced power conversion efficiency (PCE) of 3.74%, 3.86% and 4.22% under front-side illumination compared to that of pristine graphene as CEs. More importantly, under rear-side illumination the PCE of bifacial DSSCs with N-doped, S-doped and N/S dual-doped GFs as CEs can also reach 3.07%, 3.19% and 3.45%, suggesting that the doped GFs have great potential applications in fabricating bifacial DSSCs with high performance.

Bifacial dye-sensitized solar cells using highly transparent PEDOT:PSS films as counter electrodes

Highly transparent poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) films prepared by a facile spin-coating process were developed as counter electrodes for the configuration of bifacial dye-sensitized solar cells (DSSCs) with capability of utilizing the light from both sides. The used PEDOT:PSS films involved a pristine PEDOT:PSS film and ten modified PEDOT:PSS ones. The additives for preparing the modified PEDOT:PSS films were involved in iodine (IOD), dimethyl sulfoxide (DMSO), ethanol, acetone, glycerol, sorbitol and poly(ethylene glycol) (PEG) with different molecular weights (200, 400, 800 and 20,000). The UV–Vis spectra confirm that all the PEDOT:PSS films on fluorine-doped tin oxide substrates have excellent transparency with transmittance ranging from 78% to 83.5% at 550nm. The bifacial DSSC using the pristine PEDOT:PSS film exhibits the efficiencies of 4.71% and 2.38% corresponding to the illuminations from the front and the rear sides, respectively. When the additives of IOD, DMSO and PEG200 are applied to modify the pristine PEDOT:PSS film, the corresponding device shows a significantly improved efficiency of 5.19%, 5.11% and 5.29% under the front illumination and an almost unchanged efficiency under the rear illumination, respectively. The strengthened efficiency is mainly attributed to the improved catalytic activity of the modified PEDOT:PSS films induced by the coarser surface and the lower sheet resistance. Moreover, the bifacial DSSCs with the three modified PEDOT:PSS films not only have a comparable front-illuminated efficiency to the conventional Pt based DSSCs but also possess a higher rear-illuminated efficiency than the latter cells.

Alloying of platinum and molybdenum for transparent counter electrodes. A strategy of enhancing power output for bifacial dye-sensitized solar cells

Design of a cost-effective counter electrode with no sacrifice of photovoltaic performances and power output for a bifacial dye-sensitized solar cell is a persistent objective in photovoltaic power generation.

Bifacial dye-sensitized solar cells from covalent-bonded polyaniline–multiwalled carbon nanotube complex counter electrodes

Exploration of cost-effective counter electrodes (CEs) and enhancement of power conversion efficiency have been two persistent objectives for dye-sensitized solar cells (DSSCs). In the current work, polyaniline–multiwalled carbon nanotube (PANi–MWCNT) complexes are synthesized by a reflux method and employed as CE materials for bifacial DSSCs. Owing to the high optical transparency of PANi–MWCNT complex CE, the incident light from rear side can compensate for the incident light from TiO2 anode. The charge-transfer ability and electrochemical behaviors demonstrate the potential utilization of PANi–MWCNT complex CEs in robust bifacial DSSCs. The electrochemical properties as well as photovoltaic performances are optimized by adjusting MWCNT dosages. A maximum power conversion efficiency of 9.24% is recorded from the bifacial DSSC employing PANi–8 wt‰ MWCNT complex CE for both irradiation, which is better than 8.08% from pure PANi CE.

Transparent metal selenide alloy counter electrodes for high-efficiency bifacial dye-sensitized solar cells.

The 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 Co0.85 Se, 7.85 % and 4.37 % for Ni0.85 Se, 6.43 % and 4.24 % for Cu0.50 Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33 Se 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.