Nitro group as a new anchoring group for organic dyes in dye-sensitized solar cells

An organic dye JY1 bearing a nitro group was designed, synthesized and applied in DSCs. An unusual colour change was observed when the voltage applied to the device was reversed which was accompanied by a five-fold increase in the cell efficiency. We propose that applying a bias enabled the attachment of nitro groups to the TiO(2) surface.     

Organic dyes with a novel anchoring group for dye-sensitized solar cell applications

Two novel trialkylsilyl-containing organic sensitizers (JK-53 and JK-54) have been designed and synthesized. Nanocrystalline TiO₂–silica-based dye-sensitized solar cells (DSSCs) were fabricated using these dyes. Under standard global AM 1.5 solar conditions, the JK-53-sensitized cell gave a short-circuit photocurrent density (J_sc) of 6.37 mA cm^?2, an open-circuit voltage (V_oc) of 0.70 V, and a fill factor of 0.74. These values correspond to an overall conversion efficiency (η) of 3.31%. By comparison, the JK-54-sensitized cell resulted in a J_sc of 7.52 mA cm^?2, a V_oc of 0.71 V, and a fill factor of 0.75. These values give an overall conversion efficiency of 4.01%.     

A novel pyridinium hemicyanine dye with carboxylate anchoring group and its application in dye-sensitized solar cells

A novel organic dye with N-substituted pyridinium as the acceptor and carboxylate as the anchoring group were designed and synthesized for dye-sensitized solar cells, which give solar energy-to-electricity conversion efficiency (η) of up to 3.47% in comparison with the reference Ru-complex (N719 dye) with an η value of 5.27% under similar experimental conditions. This new dye is simple in structure, very easy to synthesize, and gives high V_oc.     

Patterned 3-dimensional metal grid electrodes as alternative electron collectors in dye-sensitized solar cells

We describe the application of 3-dimensional metal grid electrodes (3D-MGEs) as electron collectors in dye-sensitized solar cells (DSCs) as a replacement for fluorinated tin oxide (FTO) electrodes. Requirements, structure, advantages, and limitations of the metal grid electrodes are discussed. Solar conversion efficiencies of 6.2% have been achieved in 3D-MGE based solar cells, comparable to that fabricated on FTO (7.1%). The charge transport properties and collection efficiencies in these novel solar cells have been studied using electrochemical impedance spectroscopy.     

Highly efficient new indoline dye having strong electron-withdrawing group for zinc oxide dye-sensitized solar cell

New indoline dye (DN319) having strong electron-withdrawing dicyanovinylidene moiety and octyl group in the terminal rhodanine ring gave higher efficiency than D205, which was known as an excellent organic dye sensitizer. This result is attributed to the bathochromic shift in the UV-vis absorption band and positive shift in the E_ox level of DN319.     

Efficient thiocyanate-free sensitizer: a viable alternative to N719 dye for dye-sensitized solar cells

We have designed and synthesized a new thiocyanate-free sensitizer coded as SPS-01 and used it as the sensitizer in a TiO(2) based nanocrystalline dye-sensitized solar cell (DSSC). SPS-01 exhibits strong visible absorption properties with maximum peak around at 532 nm. The overall power conversion efficiency (PCE) of a DSSC sensitized with SPS-01 (7.96%) is higher than that of N719 (7.30%) under identical experimental conditions. This high PCE is attributed mainly due to the improvement in the short circuit current.     

Sol-gel spin coated well adhered MoO3 thin films as an alternative counter electrode for dye sensitized solar cells

In this work, we aim to develop a viable, inexpensive and non-toxic material for counter electrodes in dye sensitized solar cells (DSSCs). We employed an ultra-simple synthesis process to deposit MoO₃ thin films at low temperature by sol-gel spin coating technique. These MoO₃ films showed good transparency. It is predicted that there will be 150 times reduction of precursors cost by realizing MoO₃ thin films as a counter electrode in DSSCs compared to commercial Pt. We achieved a device efficiency of about 20 times higher than that of the previous reported values. In summary we develop a simple low cost preparation of MoO₃ films with an easily scaled up process along with good device efficiency. This work encourages the development of novel and relatively new materials and paves the way for massive reduction of industrial costs which is a prime step for commercialization of DSSCs.     

Mussel-inspired anchoring for patterning cells using polydopamine

This Article introduces a simple method of cell patterning, inspired by the mussel anchoring protein. Polydopamine (PDA), artificial polymers made from self-polymerization of dopamine (a molecule that resembles mussel-adhesive proteins), has recently been studied for its ability to make modifications on surfaces in aqueous solutions. We explored the interfacial interaction between PDA and poly(ethylene glycol) (PEG) using microcontact printing (μCP). We patterned PDA on several substrates such as glass, polystyrene, and poly(dimethylsiloxane) and realized spatially defined anchoring of mammalian cells as well as bacteria. We applied our system in investigating the relationship between areas of mammalian nuclei and that of the cells. The combination of PDA and PEG enables us to make cell patterns on common laboratorial materials in a mild and convenient fashion.     

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine(TiOPc) as hole transporting material(HTM) was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency(PCE) by minimizing recombination losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics. The β-TiOPc was applied in perovskite solar cells without dopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMe TAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties of perovskite solar cells using the TiOPc as the HTM.     

Synthesis and photovoltaic properties of polymeric metal complexes containing 8-hydroxyquinoline as dye sensitizers for dye-sensitized solar cells

Four new donor–acceptor type polymeric metal complexes (P1, P2, P3, and P4) with the same Cd(II) complex in side chain and different conjugated backbone structures were synthesized by Yamamoto coupling and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. The photophysical, electrochemical, and thermal properties were investigated in detail, showing that conjugated backbone containing fluorene improved intramolecular charge transfer and increased generation of photocurrent. The highest power conversion efficiency of 0.56% (J _sc?=?1.63?mA?cm^?2, V _oc?=?0.69?V, FF?=?0.50) was obtained with a DSSC based on P3 under simulated air mass 1.5 G solar irradiation, which shows a new strategy to design photosensitizers for DSSCs.     

An alternative electrolyte based on acetylacetone–pyridine–iodine for dye-sensitized solar cells

We prepared a new organic electrolyte by the reaction among acetylacetone, pyridine and iodine in 3-methoxypropionitrile. The UV–Visible spectra, conductivity measurement and ESI mass spectra were used to study this electrolyte. It was suggested that the quaternization reaction of pyridine took place in this electrolyte solution and two kinds of pyridinium iodide were formed. The efficiency of dye-sensitized solar cells (DSCs) using this electrolyte reaches 6.72%, which is higher than that of DSCs using LiI electrolyte and methylpropylimidazolium iodide electrolyte. It implies that these pyridinium iodides are effective alternative component of iodide for the electrolytes of DSCs. As this organic iodide electrolyte was in situ synthesized based on iodine instead of alkyl iodide, it will be cost-effective and facilitative for the production of DSCs.     

X-shaped oligothiophenes as a new class of electron donors for bulk-heterojunction solar cells

Four X-shaped oligothiophenes with different conjugation length were investigated as novel electron donors in single-layer bulk-heterojunction solar cells. The UV-vis absorption spectra of blends of compounds 1-4 with 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C(61) show a remarkably red shift and broadening with increasing thiophene number at each of the four branches. The performance of the photovoltaic cells varied significantly with molecular structures of the four oligothiophenes. Conversion efficiencies increased from 0.008% to 0.8% with changing the electron donors from 1 to 4. The maximum incident photon-to-current conversion efficiency of the device based on 4 reaches 31.6%, much higher than those of three other compounds 1-3. Remarkable improvement of the device performance was achieved with increasing the substituted thiophene number. The results show that the photovoltaic effect is dependent on the structural characteristics and the film forming abilities of the X-shaped thiophenes.     

Lanthanide complexes embedded in silicone resin as a spectral converter for solar cells

The performance of solar cell devices is dependent on various factors, and the spectral mismatch limits the upper limit of performance. Using a spectral converter to manipulate solar radiation is one way to improve solar cell efficiency. We present herein a spectral converter to move the short-wavelength (< 400 nm) range of solar radiation to the longer-wavelength range. The spectral converter comprises fluorescent lanthanide complexes uniformly embedded in silicone resin. A successful spectral converter showed transmittance of over 85%, and when applied in a Si solar cell, its relative efficiency was increased up to 4%.     

Density functional theory study on two D-π-A-type organic dyes containing different anchoring groups for dye-sensitized solar cells

The electronic structure and absorption spectra of two D-π-A-type organic dyes with different anchoring groups have been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The effect of anchoring groups on the electronic absorption of the free dyes on (TiO₂)₉ has been studied for the two carbazole dyes (MK1 and MK2). Results from DFT calculations indicate that hydroxamic acid anchoring group in MK2 lead to much stronger intermolecular charge transfer and adsorption energies on (TiO₂)₉ cluster. The effect of four different XC functionals (B3LYP, ωB97xD, M06-2X, and CAM-B3LYP) on the transition energies has been tested in order to explore the valid functional for the studied system. The wavelength values from the ωB97xD/6-31+G** level of theory are in excellent agreement with experimental data so this functional was considered to calculate the electronic absorption of the two studied dyes. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the gap energy (H–L) of the studied dyes are slightly influenced by change of anchoring group. Results reveal that the LUMO energy levels of all studied dyes are higher than the conduction band (CB) of TiO₂ (??4.00 eV). Deprotonation process enhances the efficiency of dye-sensitized solar cells during decreasing adsorption energy of dyes with (TiO₂)₉ cluster.

Graphical abstract

     

Nin-cyclohexyloxycarbonyl group as a new protecting group for tryptophan

Several new protecting groups were introduced at the Nⁱⁿ-position of tryptophan, and their reactivities were examined under the conditions used for peptide synthesis by Boc-strategy. Among them, the cyclohexyloxycarbonyl (Hoc) group was found to be the most suitable in terms of stability during elongation of the peptide chain and removability at the final HF reaction without resorting to the use of thiols.     

Alkylpyrrolidiniumtrialkoxysilyl iodides as organic iodide sources for dye-sensitised solar cells

Two new alkylpyrrolidiniumtriethoxysilyl iodides have been developed as iodide sources for DSSCs; the compound with an undecyl spacer between the siloxane and the pyrrolidinium moieties furnished higher open circuit voltages than the propyl analogue and higher efficiencies at low light intensity.     

New functional triethoxysilanes as iodide sources for dye-sensitized solar cells

Three new triethoxysilanes bearing quaternary ammonium alkyl iodides are reported, N,N,N-triethyl-3-(triethoxysilyl)propan-1-aminium iodide 1, N,N,N-triheptyl-3-(triethoxysilyl)propan-1-aminium iodide 2 and N,N,N-tridodecyl-3-(triethoxysilyl)propan-1-aminium iodide 3. ¹H and ¹³C NMR spectroscopy and electrospray mass spectrometry were used to confirm the synthesis of pure products. Electrolytes based on these ionic liquids were developed and their performance in dye-sensitized solar cells (DSSCs) evaluated. The electrolytes incorporated 1 and 2 (in 30–60 wt%) as iodide sources together with I₂ (0.08 M), 0.1 M guanidinium thiocyanate and 0.5 M tert-butylpyridine in acetonitrile (AN); and I₂ (0.15 M) and N-methylbenzimidazole (0.5 M) for 2-methoxyproprionitrile (MPN) as co-solvent. Testing of DSSCs to analyze the influence of chain length (ethyl and heptyl) on cell efficiency revealed that, for silanes concentration of 1 M, electrolyte B (based on 2 in AN) and electrolyte C (based on 1 in MPN) gave the best cell efficiency at simulated full sunlight (AM 1.5, 1000 W m⁻²) illumination (5.0–5.3%). At 0.1 Sunlight (AM 1.5, 100 W m⁻²), electrolyte B gave the best performance of 8.0%. High open circuit voltages (V_OC) of 750–850 mV were achieved for a number of quite efficient cells (5–6%). For silane 2, variation of the I⁻/I₂ ratio and total silane content (1–2 M 2) on DSSC efficiency gave a consistent efficiency of 8.0% at 0.1 Sunlight. At full sunlight, the cell efficiency decreased as the silane concentration increased from 1 M (5.0%) to 2 M (3.7%), largely due to a drop in short circuit current.