Near-Infrared Absorbing Squaraine Dyes for Solar Cells: Relationship between Architecture and Performance

Abstract

To further investigate the influence of dye architecture on dye-sensitized solar cell (DSSC) performance, some near-infrared absorbing quinoline-based squaraine dyes (4a, 4b, and 4c) with different conjugated degrees carrying carboxylic or sulfonic groups as anchoring groups were designed, prepared, and applied as sensitizers in solar cells. The photophysical and photochemical studies showed that photoelectric conversion efficiencies (η) are significantly affected by molecular structures; i.e., η of 4c with the strongest polarity and anchoring ability and the longest π electron conjugated degree was two times more than that of 4b and six times more than that of 4a. That is, the molecules with smaller optical band gap and higher molar absorption coefficient will possess better light-harvesting properties and enhanced conversion efficiency. Furthermore, all excited state orbitals relevant for the π–π electron transition both in 4b and 4c are delocalized over the anchoring groups, ensuring a strong electronic coupling to the conduction band of TiO2 and hence a fast electron transfer.

Controllable preparation of a soluble trapezoidal polyacetylene with broadband absorption by a one‐step strategy

“…The squaraine significantly possesses an absorption peak when the reaction time was more than 10 h. The P 2 with suitable broadband absorption is shown at about 40 h. Simultaneously, the resulting P 2 is completely soluble in common solvents such as THF and DMSO. 32,33 However, these peaks disappear, and the new characteristic stretching vibration absorption bands at 3020 cm 21 and 3053 cm 21 belonging to @CAH appear in the FTIR spectrum of P 1. The molecular weight of P 2 was also evaluated by a gel permeation chromatography technique to be M w 5 3.92 3 10 4 and D 5 1.89, which is twice the average molecular weight of P 1.…”

Squaraine Dyes for Dye‐Sensitized Solar Cells: Recent Advances and Future Challenges

“…Recently, Yan and co-workers reported three NIR quinolone-based symmetrical squaraine dyes, 10-12. [14] In these compounds, the anchoring groups are conjugatively linked to the quinolone donor moieties, and the influence of different anchor groups as well as the degree of conjugation between anchor and donor segments on the photophysical and photochemical properties and cell performance have been investigated. Among these three sensitizers, the absorption maximum of dye 12 reached 770 nm due to its highest polarity and longest p-electron conjugation length.…”

“…In 2005, Alex et al systematically studied the difference between several symmetrical and unsymmetrical squaraine dyes (13)(14)(15)(16)(17)(18)(19). [15] They found that the efficiencies of DSCs based on unsymmetrical squaraine dyes are better than those of symmetrical sensitizers.…”

Synthesis and photovoltaic properties of organic dyes containing N-fluoren-2-yl dithieno[3,2-b:2′,3′-d]pyrrole and different donors

“…Despite the dominance of silicon-based photovoltaic technologies, dye sensitized solar cell (DSSC) [1] invented by Grätzel has gained much impetus in recent years due to its structural modularity which allows the conversion of solar flux into electric power with high power conversion efficiency (PCE) and low cost. Light absorbers possessing optical absorptions extending into red and near-IR regions of the solar spectrum and effectively injecting electrons into the conduction band of semiconductor metallic oxides are actively searched [2]. The sensitizer adsorbed on the TiO 2 mediates the interaction between inorganic semiconductor and redox couple and control the overall performances of DSSCs.…”