Dye‐Sensitized Solar Cell Based on Novel Star‐Shaped Ruthenium Polypyridyl Sensitizer: New Insight into the Relationship between Molecular Designing and Its Outstanding Charge Carrier Dynamics

Abstract

In this work, we have introduced a star‐shaped sensitizer for dye sensitized solar cells (DSSCs) consist of three anchoring groups of benzene sulfonic acid with a significant improvement of interfacial electron transfer rate of dye/TiO2‐anatase nanostructures compared to corresponding sensitizers containing only one anchoring group. Physical chemistry aspect of the robust star‐shaped sensitizer has been investigated, employing the Current over Voltage analysis (I−V) and Transient Absorption Spectroscopy (TAS) methods. The computational studies based on density functional theory (DFT) and quantum calculations were clearly indicated that the rate of the Interfacial electron transfer (IET) significantly depends on the binding mode of a sensitizer to semiconductor surface and the nature of the electronic population in lowest unoccupied molecular orbitals (LUMOs) that initially localized on the adsorbate molecule, which is in a good agreement with experimental results. Our main result is that, among different possible binding modes of anchoring group to TiO2 surface, the bridging mode has the shortest life time of 28 fs in the presence of visible light as the excitation source. To investigate negative effect of the sensitizer molecules aggregation on TiO2 surface, on the performance of the cell, was examined the dye loading time on TiO2 surface for 10, 16 and 20 hours, which 16 hours of dye loading on surface exhibited the best DSSC performance. Moreover, transient absorption studies consistently show that the star‐shaped dye (consist of three anchoring groups) has better performance compared to the other dyes (consist of one anchoring groups) (1 and 3), in all aspects of critical parameters for DSSCs, including electron lifetime in TiO2, electron injection, dye regeneration and recombination resistance. The present work explains the fundamental physical chemistry aspects of the excited‐state in star‐shaped ruthenium polypyridyl complexes, along with opening new insight into the design of new sensitizers for enhancing the interfacial electron transfer rate and lowering the charge recombination process, which results in high power conversion efficiency of DSSC.

ZnO Nanoparticles Photosensitization Using Ruthenium(II)‐polypyridyl Isomeric Complexes

“…The relatively high efficiencies of the ruthenium(II)‐polypyridyl DSSCs can be attributed to their wide absorption range from the visible to the near‐infrared (NIR) regime. In this regard, several attempts have been made to molecularly engineer the structure of these complexes in order to increase their molar absorption coefficient, and thus their long‐term stability . This research focuses on the synthesis and characterization of ruthenium(II) complexes modified ZnO nanoparticles to use them in the design of photoanodes for DSSCs.…”

Design of a D–Di–π–A Architecture with Different Auxiliary Donors for Dye‐Sensitized Solar Cells: Density Functional Theory/Time‐Dependent‐Density Functional Theory Study of the Effect of Secondary Donors

“…The 𝜂 is influenced by the V OC and J sc , where the V OC of the DSSC is approximated by the theoretical energy difference betwixt the LUMOs of the donor molecules and acceptor TiO 2 (Equation ( 9)). [68] V OC = E LUMO − E CB (10) Here, E LUMO denotes the energy level of the organic compound, and E CB is the energy of the CB of TiO 2 (E CB = −4.0 eV). According to Equation ( 9), the computed V oc values for the examined dyes vary from 0.73 to 2.041 eV in decreasing order D1 > D2 > R = D4 > D3 > D5).…”

“…Due to their simplicity of framework redesign, highest extinction coefficients and lowest cost compared to conventional ruthenium-polypyridine complexes. [9][10][11] The most usual design for an organic sensitizer is centered on a D-𝜋-A conuration. In this design, D denotes an electronrich unit, 𝜋 is a conjugated spacer, and A indicates an electronwithdrawing moiety.…”

Conformational and Binding Effects on Interfacial Electron Transfer from Dual-Linker Sensitizers

“…Push-pull type sensitizers with electron-withdrawing bridge groups have been explored, and molecular photoswitches have been studied with the intent to control sensitizer function by external stimuli . Structural changes in the bridge have been used to tune IET and recombination by “conformational trapping.” Several studies involved chromophores that contained multiple anchor groups − or star-shaped molecules. − However, in these examples, all anchor groups served the same function. The concept of employing multiple linkers with different functions, for example, one linker for stable chemical attachment to the surface and another one for promoting interaction between the sensitizer and the interface, is an approach that gives more flexibility in the design of sensitizers and can add functionalities beyond IET.…”