Control of Molecular Arrangement and/or Orientation of D–π–A Fluorescent Dyes for Dye-sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) based on organic dyes adsorbed on TiO 2 electrodes, which emerged as a new generation of sustainable photovoltaic devices, have received considerable attention because of high incident solar light-toelectricity conversion efficiency and low cost of production. The aim of this Highlight Review is to indicate the importance of creating effective D³A dye sensitizers capable of controlling not only photophysical and electrochemical properties of the dyes themselves but also molecular arrangement and/or orientation of the dyes on TiO 2 surface to provide a good electron communication between the dye and TiO 2 electrode, for developing high-performance DSSCs.

Theoretical Design of High-Performance Boron Dipyrromethenes Dyes by Introducing Heterocyclics to Tune Photoelectric Properties

“…Therefore, it is necessary to design and synthesize high-efficiency sensitizers for improving the performance of DSSC devices. At present, dye sensitizers that have been massively studied include porphyrin and its metal complexes, − ruthenium-based compounds, , and metal-free organic dyes. , Extremely, metal-free organic dyes have stimulated research interest because of their low production cost, strong light absorption, and easy structural modification. , A variety of metal-free organic dyes have been widely used in DSSCs, such as cyanine dyes, coumarins dyes, indoline dyes, and organic compounds with the donor−π conjugated bridge–acceptor (D−π–A) structure. Among them, D−π–A dyes in particular have attracted much attention because the synthetic flexibility in the structural design. , Additionally, based on the D−π–A type, series of novel structures including D–D−π–A, D–A−π–A, D−π–D–A, and D−π–A–A type have been developed.…”

“…10,11 Extremely, metal-free organic dyes have stimulated research interest because of their low production cost, strong light absorption, and easy structural modification. 12,13 A variety of metal-free organic dyes have been widely used in DSSCs, such as cyanine dyes, 14 coumarins dyes, 15 indoline dyes, 16 and organic compounds with the donor−π conjugated bridge−acceptor (D−π−A) structure. Among them, D−π−A dyes in particular have attracted much attention because the synthetic flexibility in the structural design.…”

Intramolecular Exciton-Coupled Squaraine Dyes for Dye-Sensitized Solar Cells

“…Among these aspects, the development of sensitizers appears to provide a way to achieve a significant boost in the final efficiency of DSSCs. Metal complexes (typified by ruthenium polypyridyl complexes) have been demonstrated to be successful sensitizers for TiO 2 -based DSSCs. − Metal-free organic sensitizers have shown cost-effectiveness, excellent molar extinction coefficients, and flexibility in molecular design, allowing modifications of their electronic and steric structures through molecular engineering. − A variety of metal-free sensitizers such as coumarin dyes, indoline dyes, cyanine dyes, and π-conjugated compounds in which donor and acceptor components were linked π-linkers (D-π-A dyes) have been reported. D-π-A dyes in particular have contributed to the significant improvement of DSSC performance to date because of their great flexibility in molecular design. − …”

Interplay between π-Bridges and Positions of Branched Alkyl Groups of Unsymmetrical D–A–D−π–A Squaraines in Dye-Sensitized Solar Cells: Mode of Dye Anchoring and the Charge Transfer Process at the TiO2/Dye/Electrolyte Interface

“…There are many parameters that govern the solar cell efficiency of polymethine dyes apart from photophysical and electrochemical properties. Self-assembly and orientation of dyes on TiO 2 play an important role in achieving high-efficiency cells. , Controlling the dye orientation on the surface by changing the length and position of in-plane and out-of-plane hydrophobic functionalities; type, number, and position of anchoring groups; dipping solvents; coadsorbents; and cosensitizers are explored in the literature. − Unsymmetrical squaraines DTS-CA and DTS-PA showed the effect of out-of-plane alkyl-functionalized π-spacers and different anchoring groups on PCE. The unsymmetrical squaraine structure of the silalodithiophene π-spacer possessing out-of-plane branched alkyl groups displayed a power conversion efficiency (PCE) of 8.9%, implying both electronic and steric effects .…”