A hybrid soft solar cell based on the mycobacterial porin MspA linked to a sensitizer-viologen diad

A prototype of a nano solar cell containing the mycobacterial channel protein MspA has been successfully designed. MspA, an octameric transmembrane channel protein from Mycobacterium smegmatis, is one of the most stable proteins known to date. Eight Ruthenium(II) aminophenanthroline-viologen maleimide Diads (Ru-Diads) have been successfully bound to the MspA mutant MspAA96C via cysteine-maleimide bonds. MspA is known to form double layers in which it acts as nanoscopic surfactant. The nanostructured layer that is formed by (Ru-Diad)(8)MspA at the TiO2 electrode is photochemically active. The resulting "protein nano solar cell" features an incident photon conversion efficiency of 1% at 400 nm. This can be regarded as a proof-of-principle that stable proteins can be successfully integrated into the design of solar cells

Excited State Charge Separation in Solution and in Electropolymerized Films of Terthiophene-Fullerene Dyad and Phenothiazine-Terthiophene-Fullerene Triad

This article reports synthesis, X-ray structure and excited state events occurring in a terthiophene-C₆₀ dyad (TT-C₆₀), and a phenothiazine-terthiophene-C₆₀ triad (PTZ-TT-C₆₀)

Chloring e6 Sensitized Photovoltaic Cells: Effect of Co-Adsorbents on Cell Performance, Charge Transfer Resistance, and Charge Recombination Dynamics

This article investigates the effect of dye-aggregation-preventing co-adsorbents, cholic acid and deoxycholic acid, on the performance of dye-sensitized solar cells constructed using a metal-free sensitizer, chlorin e6 adsorbed onto TiO₂ surface

Supramolecular Donor–Acceptor Assembly Derived from Tetracarbazole–Zinc Phthalocyanine Coordinated to Fullerene: Design, Synthesis, Photochemical, and Photoelectrochemical Studies

A functional photosynthetic antenna–reaction center mimicking donor–acceptor polyad has been newly designed, synthesized, and characterized. The polyad was comprised of four entities of carbazole covalently linked to the macrocycle periphery of a zinc phthalocyanine (ZnPc). Efficient singlet excitation transfer from the carbazole to zinc phthalocyanine has been witnessed from the emission studies. Axial coordination of phenylimidazole-functionalized fulleropyrrolidine to ZnPc served as an electron acceptor in the polyad. Optical absorption and emission along with computational studies revealed stable complex formation wherein the evaluated binding constant <i>K</i> was 7.7 ± 0.2 × 10⁵ M^–1, an order of magnitude higher than that observed earlier for similar complexes due to the electronic effect induced by the carbazole entities. From the free-energy calculations, photoinduced electron transfer from the ¹ZnPc* to fullerene within the polyad was established to be an exothermic process. Kinetics of charge separation, <i>k</i>_CS, monitored by time-resolved emission was found to be 2.8 × 10⁹ s^–1, indicating a relatively fast charge-separation process. The electron-transfer products were characterized by nanosecond transient absorption spectroscopic technique; the presence of ZnPc^+• radical cation at 890 nm and fulleropyrrolidine anion radical at 1000 nm was clear from this study. The kinetics of charge recombination, <i>k</i>_CR, evaluated from the decay of either of the radical ions, was found to be 6.25 ± 0.2 × 10⁷ s^–1, revealing the persistence of the radical ion-pair species to some extent. Further, photoelectrochemical studies, performed by constructing photocells by electrophoretic deposition of the studied polyad on nanocrystalline SnO₂ modified surface, revealed a higher value of incident photon-to-current conversion efficiency covering the wide visible–near IR spectral region and good on–off switchability. Better charge injection from the excited polyad to the conduction band of the semiconductor was evident from the electrochemical impedance spectral measurements of electron recombination resistance calculations

Excited State Charge Separation in Solution and in Electropolymerized Films of Terthiophene-Fullerene Dyad and Phenothiazine-Terthiophene-Fullerene Triad

This article reports synthesis, X-ray structure and excited state events occurring in a terthiophene-C₆₀ dyad (TT-C₆₀), and a phenothiazine-terthiophene-C₆₀ triad (PTZ-TT-C₆₀)

Phenothiazine-Sensitized Organic Solar Cells: Effect of Dye Anchor Group Positioning on the Cell Performance

Effect of positioning of the cyanoacrylic acid anchoring group on ring periphery of phenothiazine dye on the performance of dye-sensitized solar cells (DSSCs) is reported. Two types of dyes, one having substitution on the C-3 aromatic ring (Type 1) and another through the N-terminal (Type 2), have been synthesized for this purpose. Absorption and fluorescence studies have been performed to visualize the effect of substitution pattern on the spectral coverage and electrochemical studies to monitor the tuning of redox levels. B3LYP/6-31G* studies are performed to visualize the frontier orbital location and their significance in charge injection when surface modified on semiconducting TiO₂. New DSSCs have been built on nanocrystalline TiO₂ according to traditional two-electrode Grätzel solar cell setup with a reference cell based on N719 dye for comparison. The lifetime of the adsorbed phenothiazine dye is found to be quenched significantly upon immobilizing on TiO₂ suggesting charge injection from excited dye to semiconducting TiO₂. The performances of the cells are found to be prominent for solar cells made out of Type 1 dyes compared to Type 2 dyes. This trend has been rationalized on the basis of spectral, electrochemical, computational, and electrochemical impedance spectroscopy results

Control over Photoinduced Energy and Electron Transfer in Supramolecular Polyads of Covalently linked azaBODIPY-Bisporphyrin ‘Molecular Clip’ Hosting Fullerene

A ‘molecular clip’ featuring a near-IR emitting fluorophore, BF₂-chelated tetraarylazadipyrromethane (aza-BODIPY) covalently linked to two porphyrins (MP, M = 2H or Zn) has been newly synthesized to host a three-dimensional electron acceptor fullerene via a ‘two-point’ metal–ligand axial coordination. Efficient singlet–singlet excitation transfer from ¹ZnP* to aza-BODIPY was witnessed in the dyad and triad in nonpolar and less polar solvents, such as toluene and <i>o</i>-dichlorobenzene, however, in polar solvents, additional electron transfer occurred along with energy transfer. A supramolecular tetrad was formed by assembling bis-pyridine functionalized fullerene via a ‘two-point’ metal–ligand axial coordination, and the resulted complex was characterized by optical absorption and emission, computational, and electrochemical methods. Electron transfer from photoexcited zinc porphyrin to C₆₀ is witnessed in the supramolecular tetrad from the femtosecond transient absorption spectral studies. Further, the supramolecular polyads (triad or tetrad) were utilized to build photoelectrochemical cells to check their ability to convert light into electricity by fabricating FTO/SnO₂/polyad electrodes. The presence of azaBODIPY and fullerene entities of the tetrad improved the overall light energy conversion efficiency. An incident photon-to-current conversion efficiency of up to 17% has been achieved for the tetrad modified electrode