Enhancement in the photostability of natural dyes for dye‐sensitized solar cell (DSSC) applications: a review

The advancements in the generation of solar cells have created a landmark to design a cost‐effective, less weight, biocompatible, and environmental‐friendly solar cell. Dye‐sensitized solar cells (DSSCs) have become a topic of significant research in the recent years because of their imperative role in the zone of harvesting energy from the renewable source, and it appears to be a promising candidate for the triumph because of its low cost and ease of preparation. The use of synthetic dyes as a sensitizer for DSSC provides better efficiency and high durability. Unfortunately, they suffer from several margins such as higher cost and usage of toxic materials. These downsides have opened up for alternative sensitizer such as biocompatible natural dyes. Natural dyes contain plant pigments such as carotenoid, flavonoid, betalains, and chlorophyll that act as sensitizers (dye) for DSSC. But, the efficiency of natural dyes is not up to the mark mainly due to photoinstability of natural dye in the presence of sunlight that leads to photodegradation. The stability issues are mainly due to interaction of natural dyes with photoelectrode. The photoelectrodes in DSSC are semiconductor materials with superior characteristic of photocatalytic activity (PCA). The PCA of titanium dioxide (TiO₂) generates high energetic free electrons on the surface of film that produce free radical ions in contact with moisture. These free radical ions readily degrade the organic matter present nearby (natural dye in DSSC). Thus, the PCA of photoelectrode is responsible for the photodegradation of dyes causing photoinstability. The main objective of this review is to study the photoinstability of natural dyes in DSSC. In this regard, the DSSC is concentrated into sections, and the stability issues due to PCA of photoelectrode are studied individually in the view of considering the DSSC operating with iodide‐based electrolytes and platinum as counter electrode only. Various algae groups are featured as a study tool to overview the dye interaction with photoelectrode. It highlights the application of Z‐scheme of photosynthesis to DSSC to have a broader perception on the working of DSSC and also shows some of the ways for improving the stability of dyes by suppressing or reducing the PCA of photoelectrode. Copyright © 2017 John Wiley & Sons, Ltd.     

Synthesis of TiO2 nanoparticles at low hydrothermal temperature and its performance for DSSC sensitized using natural dye extracted from Melastoma malabathricum L. seeds

Efficiency of a dye‐sensitized solar cell (DSSC) device depends on its semiconductor layer and the sensitizing dye to absorb the light. This work seeks to obtain the best solvent for the natural dye extraction from Melastoma malabathricum L. seeds. The extracted dye is used as sensitizer on TiO₂ nanoparticles produced via hydrothermal but optimized at relatively low temperature. Infrared characterization of the extracted dyes showed differences in functional groups using different solvents, whereas ultraviolet visible examination of the dyes showed differences in intensity along the spectrum ranges of 600 to 400 nm with maximum absorption around 550 to 500 nm. Thermal analysis revealed that the natural dye should be stable around room temperature. Analysis on the synthesized TiO₂ nanoparticles showed that the average crystallite size reported in the previous work is consistent with crystallite sizes observed in the transmission electron microscope images. Photoactivity examination showed that the DSSC sensitized using natural dye extracted with ethanol containing 20% distilled water on TiO₂ synthesized at 150°C has an efficiency of 5.7%, whereas the one on commercial TiO₂ P25 Degussa has an efficiency of 3.0%. The DSSC device sensitized using commercial dye on TiO₂ synthesized at 150°C has an efficiency of 4.4%, whereas the one on TiO₂ P25 Degussa has an efficiency of 4.0%. This result is promising for further development of the DSSC device using TiO₂ nanoparticles synthesized at low hydrothermal temperature and sensitized with the natural dye.     

St. Lucie cherry,yellow jasmine,and madder berries as novel natural sensitizers for dye‐sensitized solar cells

Natural dyes extracted from fruits, vegetables, flowers, and leaves are considered as promising alternative sensitizers to replace synthetic dyes for dye‐sensitized solar cells (DSSCs). Generally, solar activity of natural dyes stem from anthocyanin pigment. Carbonyl, carboxyl, and hydroxyl groups present in the anthocyanin molecule improve the adsorption ability of dye on TiO₂ and therefore facilitate charge transfer. Here, for the first time, novel natural dyes extracted from St. Lucie cherry, yellow jasmine, and madder berries are reported to act as sensitizer in DSSCs. These novel natural dye extracts are prepared by dissolving related fruits in ethanol. The ingredient of the dyes is identified by FT‐IR spectroscopy. Accordingly, FT‐IR spectrum reveals that novel natural dye extracts exhibit all the characteristic peaks of anthocyanin pigment. Specifically, St. Lucie cherry consists of more distinct carbonyl group than other sources. Also, photoanodes composed of three TiO₂ layers are prepared by using a spin‐coating method. Then, they are immersed into natural dyes and analyzed by conducting UV‐Vis spectroscopy. Compared with bare TiO₂, natural dye–loaded photoanodes demonstrate far higher absorption ability in the visible region. After fabrication of devices with different novel natural dye sensitizers, current‐voltage characteristics and electrochemical impedance spectroscopy measurements are performed. The best power conversion efficiency (PCE) of 0.19% is obtained by sensitization of St. Lucie cherry with an open‐circuit voltage (V_oc) of 0.56 V, short‐circuit current density (J_sc) of 181 μA cm^?2, and fill factor (FF) of 0.55. Furthermore, St. Lucie cherry–sensitized devices show the lowest charge transfer and highest recombination resistances. This result can be attributed to the obvious carbonyl group exhibited by St. Lucie cherry.     

Novel dye based photoelectrode for improvement of solar cell conversion efficiency

We have explored the application of natural dyes extracted from beetroot in Dye sensitized solar cell (DSSC). The main pigment is betacyanin which was obtained by separation and purification from the extract. The photo electrochemical performance of the DSSC based on these dyes showed that the photo voltage and photocurrent 435 mV, 9.86 mA, respectively. The overall conversion efficiency of nano WO₃ coated TiO₂ dye-sensitized solar cells exhibits a higher conversion efficiency of 2.2%. The photo electrochemical performance of beetroot extract demonstrate that betacyanin dye was the most effectual component of the sensitizer for DSSC because of the simple preparation technique, widely available and low cheap cost.     

Effect of using betalain,anthocyanin and chlorophyll dyes together as a sensitizer on enhancing the efficiency of dye-sensitized solar cell

The paper explored the mechanism of working of dye sensitizers for the improvement of efficiency of environmentally benign dye-sensitized solar cells (DSSC). The identified natural dyes namely anthocyanin (A), betalain (B) and chlorophyll (C) were extracted from Roselle (Hibiscus sabdariffa L.), spinach (Spinacia oleracea) and beetroot (Beta vulgaris) respectively. Light absorption performance of dyes was recorded by ultraviolet-visible (UV-vis) spectroscopic analysis followed by direct and indirect band gap calculation. The effect of functional groups present in the dyes studied by Fourier transform infrared spectroscopy (FTIR) and binding of the dyes on TiO₂ through surface morphology of sheets was identified employing field emission scanning electron microscopy (FESEM). Photovoltage characteristics (I-V) and induced photon to current efficiency (IPCE) measurements were also noted followed by the stability studies. The N3 (synthetic dye chosen for the reference) dye-based cell showed the highest efficiency of 6.19% out of all of 11 cells fabricated using different sensitizers. The DSSC fabricated using the novel mixed dye (ABC) mixture gave the highest efficiency of 3.73%, however it showed similar drop (almost 22%) in efficiency as that with of N3 dye in stability studies. The mechanism for the increase in the overall power conversion efficiency of DSSC was also suggested.     

Optimization of paste formulation for TiO2 nanoparticles with wide range of size distribution for its application in dye sensitized solar cells

Dye sensitized solar cell (DSSC) can be an economically viable and technically simpler alternate to the silicon based solar cells. Films of nanocrystalline titanium dioxide (TiO₂) are considered as the most suitable photoelectrode for DSSC. For this study, TiO₂ powder of anatase phase, synthesized in acidic environment was used. The average diameter of the nanoparticles was ～20 nm and BET surface area was 64.68 m²/g. Different TiO₂ pastes were prepared by varying the proportion of TiO₂ powder, α-terpineol, and ethyl cellulose (EC) in their composition. The TiO₂ paste was cast on fluorine doped tin oxide (FTO) coated glass surface using doctor blade to prepare photoelectrode of TiO₂ film. Composition of the paste ingredients was optimized by comparing the conversion efficiencies of the DSSCs fabricated with the photoelectrode of thickness ～18 μm. The outcome of this study can be crucial for the preparation of reliable TiO₂ paste in a simple way for its application in DSSC.     

Performance of the dye‐sensitized solar cells fabricated using natural dyes from Ixora coccinea flowers and Cymbopogon schoenanthus leaves as sensitizers

In this study, the chlorophyll and anthocyanin natural dyes were extracted from Cymbopogon schoenanthus leaves and Ixora coccinea flowers, respectively. Thereafter, these dyes were used as sensitizers in the TiO₂‐based dye‐sensitized solar cells (DSSCs). Ten solvents were used for solubilizing the dyes. Amongst the 10 solvents, the ethanol showed the highest absorption spectra for the anthocyanin and chlorophyll molecules. Temperature significantly affected the yield of the natural dyes. It was seen that an optimal extraction temperature of 70°C and 80°C results to higher anthocyanin and chlorophyll yields, respectively. However, an extraction temperature above 70°C and 80°C has shown a sharply decrease in the anthocyanin and chlorophyll concentrations, respectively. Also, the solution of acidic extraction, especially with a pH value of 4, increased the dyes concentrations. As seen in the results, the chlorophyll‐sensitized DSSCs had 0.23% conversion efficiency (?), short‐circuit current (I_sc) of 0.9 mA/cm^–2, open‐circuit voltage (V_oc) of 0.51 V, and 49.13% fill factor (FF). Meanwhile, the anthocyanin‐sensitized DSSCs showed 0.16% ?, 0.4 mA/cm^–2 I_sc, 0.53 V V_oc, and 75.93% FF.     

On the photophysical and electrochemical studies of dye-sensitized solar cells with the new dye CYC-B1

In this study, the photoelectrochemical characteristics of a ruthenium photosensitizer with an alkyl bithiophene group, designated as CYC-B1, are studied. The effect of mesoporous TiO₂ film thickness on the photovoltaic performance of CYC-B1 and N3 dye-sensitized solar cells was investigated. The performance of the dye-sensitized nanocrystalline TiO₂ solar cells (DSSC) fabricated using CYC-B1 dye-anchored TiO₂ photoelectrode showed a convincing enhancement in cell efficiency when the TiO₂ film thickness was increased from 3 μm (eff.=5.41%) to 6 μm (eff.=7.19%). The efficiency of the CYC-B1-sensitized DSSC was maximum at 6 μm of the TiO₂ film thickness, reached its limiting value and remained constant up to 53 μm, although a similar trend was also observed for N3 dye-sensitized DSSC, however, the maximum efficiency achieved was only at 27 μm thickness (eff.=6.75%). As expected, the photocurrent density generated in the DSSC modified by CYC-B1 dye is larger than that from N3 dye. The effect of guanidinium thiocyanate (GuSCN) (additive) addition to the electrolyte on the photovoltaic performance of DSSCs based on CYC-B1 was also investigated. Furthermore, the electrochemical impedance spectroscopy (EIS) technique and photo-transient laser method have been employed to analyze the charge transfer resistances (R_ct) and the lifetime of the injected electrons on the TiO₂ containing different thicknesses.     

Dye-sensitized solar cell using natural dyes extracted from rosella and blue pea flowers

Dye-sensitized solar cells (DSSCs) were fabricated using natural dyes extracted from rosella, blue pea and a mixture of the extracts. The light absorption spectrum of the mixed extract contained peaks corresponding to the contributions from both rosella and blue pea extracts. However, the mixed extract adsorbed on TiO₂ does not show synergistic light absorption and photosensitization compared to the individual extracts. Instead, the cell sensitized by the rosella extract alone showed the best sensitization, which was in agreement with the broadest spectrum of the extract adsorbed on TiO₂ film. In case that the dyes were extracted at , using water as extracting solvent, the energy conversion efficiency (η) of the cells consisting of rosella extract alone, blue pea extract alone and mixed extract was 0.37%, 0.05% and 0.15%, respectively. The sensitization performance related to interaction between the dye and TiO₂ surface is discussed. The explanations are supported by the light absorption of the extract solution compared to extracts adsorbed on TiO₂ and also dye structures. The effects of changing extracting temperature, extracting solvent and pH of the extract solution are also reported. The efficiency of rosella extract sensitized DSSC was improved from 0.37% to 0.70% when the aqueous dye was extracted at instead of and pH of the dye was adjusted from 3.2 to 1.0. Moreover, DSSC stability was also improved by the changes in conditions. However, the efficiency of a DSSC using ethanol as extracting solvent was found to be diminished after being exposed to the simulated sunlight for a short period.     

Soft‐template synthesis of high surface area mesoporous titanium dioxide for dye‐sensitized solar cells

In the present work, 10 to 14 nm titania nanoparticles with high‐packing density are synthesized by the soft‐template method using a range of cationic surfactants including cetyl trimethylammonium bromide (CTAB), Sodium dodecyl sulfate (SDS), and dodecyl trimethylammonium bromide (DTAB). The synthesized nanoparticles are used as a photoanode material in dye solar cells. Density functional theory (DFT) simulations reproduce our experimental results of charge transfer and strong interaction between the TiO₂ and N719. N719‐TiO₂ complex establishes strong electrostatic bonding through H of the dye with the O of TiO₂ surface. Solar cell efficiency of 6.08% with 12.63 mA/cm², 793 mV, and 48.5% for short circuit current density, open circuit voltage, and fill factor, respectively, are obtained under 1 sun illumination for the dye‐sensitized solar cell (DSSC) using a film of mesoporous TiO₂ synthesized from the SDS surfactant. On the other hand, the 21 nm commercial TiO₂ powder (P25) device results in 4.60% efficiency under similar conditions. Electrochemical impedance spectroscopic studies show that the SDS device has lesser charge transport resistance than the other devices because of its higher surface area, packing density, and dye loading capacity. Our results show that employing high packing density‐based TiO₂ nanoparticles represents a commercially viable approach for highly beneficial photoanode development for future DSSC applications.     

Study on dye-sensitized solar cell using novel infrared dye

The performances of infrared-dye-sensitized solar cells fabricated using two novel cyanine dyes (light absorption edge: 900 nm) were investigated. The performance of the cell using NK6037 dye was superior to that using NK4432; hence, an intimate interaction between the dye and the TiO₂ photoelectrode via the functional group is essential for efficient electron injection. The efficiency reached 1.9% by optimizing the light-confining effect of the TiO₂ photoelectrode and TiO₂ film thickness, and reached 2.3% by adjusting the concentration of deoxycholic acid (DCA) in the dye solution. The roles of the dye and DCA were clarified by photochemical and electrochemical characterization.     

Reduced graphene oxide–titania nanocomposite‐modified photoanode for efficient dye‐sensitized solar cells

We report the successful application of reduced graphene oxide–titania (rGO–TiO₂) nanocomposite as an efficient photoanode for dye‐sensitized solar cell (DSSC). The DSSC assembled with the rGO–TiO₂‐modified photoanode demonstrated an enhanced solar to electrical energy conversion efficiency of 4.74% compared with the photoanode of DSSC composed with unmodified TiO₂ (2.19%) under full sunlight illumination (100 mW/cm², AM 1.5G) as a result of the better charge collection efficiency of rGO, which reduced the back electron transfer process. Influence of the rGO content on the overall efficiency was also investigated, and the optimal rGO content for TiO₂ was 0.5 mg. Further, the modification of rGO–TiO₂ on the compact layer TiO₂ surface led to an increase in efficiency to 5.83%. The superior charge collection and enhanced solar energy conversion efficiency of the rGO–TiO₂ nanocomposite makes it to be used as a promising alternative to conventional photoanode‐based DSSCs. Copyright © 2015 John Wiley & Sons, Ltd.     

Triphenylamine- and benzothiadiazole-based dyes with multiple acceptors for application in dye-sensitized solar cells

Two novel dyes TPAR3 and BTDR2 based on triphenylamine and benzothiadiazole, respectively, with multiple electron acceptors were synthesized and characterized by FT-IR, ¹H NMR, TGA and thermomechanical analysis (TMA). They carried terminal cyanoacrylic acid electron acceptors/anchoring moieties, which were connected with the central unit through a thiophene ring. The absorption bands of the dyes were extended up to ∼570 nm with long-wave absorption maximum at 425-455 nm and optical band gap of 2.10-2.17 eV. The dyes emitted yellow-orange light with photoluminescence maximum at 547-615 nm. We have investigated the photovoltaic properties of quasi solid state dye sensitized solar cells (DSSCs) based on these metal free organic dyes. It has been found that the power conversion efficiency of the DSSCs based on composite zinc titanium oxide (ZTO) nanocrystalline photoelectrode is higher than that for TiO₂ based DSSCs. This has been attributed to the longer electron lifetime and more negative conduction band edge of ZTO. The overall power conversion efficiency of the DSSCs based on TPAR3 and BTDR2 employing ZTO photoelectrode is 6.3% and 3.6%, respectively. These results indicate that both the acceptor moiety of metal free organic dyes and ZTO photoelectrode have an effect on the photovoltaic performance of DSSCs.     

Anchorage of N3 dye-linked polyacrylic acid to TiO2/electrolyte interface for improvement in the performance of a dye-sensitized solar cell

A synthetic route was developed to link N3 dye to polyacrylic acid (PAA) using ethylenediamine (en) as the linker. The resulting complex, PAA–en–N3, was then coated onto a TiO₂ film. The modified TiO₂ film electrode (hereafter PAA–en–N3/TiO₂), when used as the photoanode in a dye-sensitized solar cell (DSSC), exhibited enhanced solar energy conversion efficiency compared with that of the usual DSSC with the N3/TiO₂ film electrode. The increase in efficiency was attributed to the increased open-circuit voltage (V_oc) and short-circuit photocurrent (J_sc). The increase in V_oc was attributed to the formation of a hydrophobic PAA–en–N3 layer on the TiO₂/electrolyte interface, while the increase in J_sc was attributed to the additional dye acquired by the TiO₂ film from the PAA–en–N3 complex.     

Efficient sensitization of nanocrystalline TiO2 films with cyanine and merocyanine organic dyes

Various kinds of cyanine and merocyanine organic dyes having short anchoring groups as sensitizers on nanocrystalline TiO₂ electrodes were investigated to promote the short-circuit photocurrent (J_sc) and the solar light-to-power conversion efficiency (η_sun). The J_sc and η_sun improved when the three different three dyes (yellow and red cyanine dyes, and blue squarylium cyanine dye) were adsorbed simultaneously on a TiO₂ electrode, as compared with the J_sc and η_sun of the TiO₂ electrodes adsorbed by each single dye. The maximum η_sun was 3.1% (AM-1.5, 100 mW/cm²). The J_sc and η_sun were influenced by the solvents for the dye adsorption on the TiO₂ electrode, and the efficiencies were improved by the addition of some cholic acids into the dye solution for adsorption. The electron transfer and/or the energy transfer from the red cyanine dye to the blue cyanine dye was observed on a SiO₂ film using emission spectroscopy, suggesting a strong interaction between two dyes. The J-like aggregates of the blue cyanine dyes hardly showed sensitization efficiency.     

Influence of electrolyte on the photovoltaic performance of a dye-sensitized TiO2 solar cell based on a Ru(II) terpyridyl complex photosensitizer

We have investigated the influence of electrolyte composition on the photovoltaic performance of a dye-sensitized nanocrystalline TiO₂ solar cell (DSSC) based on a Ru(II) terpyridyl complex photosensitizer (the black dye). We have also spectroscopically investigated the interaction between the electrolyte components and the adsorbed dye. The absorption peaks attributed to the metal-to-ligand charge transfer transitions of the black dye in solution and adsorbed on a TiO₂ film, were red-shifted in the presence of Li cations, which led to an expansion of the spectral response of the solar cell toward the near-IR region. The photovoltaic performance of the DSSC based on the black dye depended remarkably on the electrolyte composition. We developed a novel efficient organic liquid electrolyte containing an imidazolium iodide such as 1,2-dimethyl-3-n-propylimidazolium iodide or 1-ethyl-3-methylimidazolium iodide (EMImI) for a DSSC based on the black dye. A high solar energy-to-electricity conversion efficiency of 9.2% (J_sc=19.0 mA cm⁻², V_oc=0.67 V, and FF=0.72) was attained under AM 1.5 irradiation (100 mW cm⁻²) using a novel electrolyte consisting of 1.5 M EMImI, 0.05 M iodine, and acetonitrile as a solvent with an antireflection film.     

Aqueous dye-sensitized solar cell based on new ruthenium diphenyl carbazide complexes

The major challenge of the operation of every solar cell based on dye including water splitting solar cell (WSSC) and dye sensitized solar cell (DSSC) is the using organic solvent medium which causes to decompose the solar cell structure, resulting environmental impact. Here, we synthesized and characterized two new ruthenium complexes with nitrogen and oxygen donor ligands for DSSC application which show good stability on TiO₂ surface in water solvent. Interestingly, the DSSC based on [Ru(dcbpy)₂(DPC)]Cl, where dcbpy = 4,4-dicarboxilic acid 2,2-bipyridin and DPC = diphenylcarbazide, was shown better efficiency in water than methanol dye loading as well as N3 as a benchmark sensitizer in the same condition. The DPC-based exhibited open circuit voltage (V_oc) of 0.63 V, short-circuit current density (J_sc) of 2.5 mA/cm² and fill factor (FF) of 70%, resulting an overall power efficiency of 1.12%. The incident-photon-to-current conversion efficiency (IPCE) value is also reached to 45% for [Ru(dcbpy)₂(DPC)]Cl in the same condition It is proposed that the ruthenium complex containing nitrogen and oxygen donor ligands is more stability on TiO₂ and prevent the decomposition of TiO₂ porous under water solvent condition.     

Natural dyes as photosensitizers for dye-sensitized solar cell

The dye-sensitized solar cells (DSC) were assembled by using natural dyes extracted from black rice, capsicum, erythrina variegata flower, rosa xanthina, and kelp as sensitizers. The I_SC from 1.142 mA to 0.225 mA, the V_OC from 0.551 V to 0.412 V, the fill factor from 0.52 to 0.63, and P_max from 58 μW to 327 μW were obtained from the DSC sensitized with natural dye extracts. In the extracts of natural fruit, leaves and flower chosen, the black rice extract performed the best photosensitized effect, which was due to the better interaction between the carbonyl and hydroxyl groups of anthocyanin molecule on black rice extract and the surface of TiO₂ porous film. The blue-shift of absorption wavelength of the black rice extract in ethanol solution on TiO₂ film and the blue-shift phenomenon from absorption spectrum to photoaction spectrum of DSC sensitized with black rice extract are discussed in the paper. Because of the simple preparation technique, widely available and low cheap cost natural dye as an alternative sensitizer for dye-sensitized solar cell is promising.     

Pomegranate leaves and mulberry fruit as natural sensitizers for dye-sensitized solar cells

This study employs chlorophyll extract from pomegranate leaf and anthocyanin extract from mulberry fruit as the natural dyes for a dye-sensitized solar cell (DSSC). A self-developed nanofluid synthesis system is employed to prepare TiO₂ nanofluid with an average particle size of 25 nm. Electrophoresis deposition was performed to deposit TiO₂ nanoparticles on the indium tin oxide (ITO) conductive glass, forming a TiO₂ thin film with the thickness of 11 μm. Furthermore, this TiO₂ thin film was sintered at 450 °C to enhance the thin film compactness. Sputtering was used to prepare counter electrode by depositing Pt thin film on FTO glass at a thickness of 20 nm. The electrodes, electrolyte (), and dyes were assembled into a cell module and illuminated by a light source simulating AM 1.5 with a light strength of 100 mW/cm² to measure the photoelectric conversion efficiency of the prepared DSSCs. According to experimental results, the conversion efficiency of the DSSCs prepared by chlorophyll dyes from pomegranate leaf extract is 0.597%, with open-circuit voltage (V_OC) of 0.56 V, short-circuit current density (J_SC) of 2.05 mA/cm², and fill factor (FF) of 0.52. The conversion efficiency of the DSSCs prepared by anthocyanin dyes from mulberry extract is 0.548%, with V_OC of 0.555 V and J_SC of 1.89 mA/cm² and FF of 0.53. The conversion efficiency is 0.722% for chlorophyll and anthocyanin as the dye mixture, with V_OC of 0.53 V, J_SC of 2.8 mA/cm², and FF of 0.49.     

Low cost photovoltaic modules based on dye sensitized nanocrystalline titanium dioxide and carbon powder

A new type of photovoltaic module based on monolithically series connected dye sensitized photoelectrochemical cells is described. Each solar cell element consists of three porous layers on a transparent conducting substrate, namely a photoelectrode of dye sensitized nanocrystalline TiO₂ (anatase), a spacer of electrically insulating, light reflecting particles of TiO₂ (rutile), and a counterelectrode of graphite powder and carbon black. The pores of these layers are filled with a redox electrolyte containing iodide for hole transport between photo- and counterelectrode. The monolithic series connection on the transparent conducting substrate, e.g., SnO₂ coated glass, is achieved by simple overlap of each carbon counterelectrode with the back contact of the adjacent photoelectrode. Such modules may be produced in a continuous non-vacuum process by simple printing techniques. In this paper we present the first results on energy conversion efficiency and long term stability obtained with this new type of solar cell.