Design of NIR-Absorbing Simple Asymmetric Squaraine Dyes Carrying Indoline Moieties for Use in Dye-Sensitized Solar Cells with Pt-Free Electrodes

Abstract

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.

Polymethine Dyes in Hybrid Photovoltaics: Structure–Properties Relationships

“…The same group also reported in 2012 two squaraines substituted with the same hindered heterocycle [S129,130] to avoid the use of π‐spacing groups 124…”

Near‐Infrared‐Absorbing Metal‐Free Organic, Porphyrin, and Phthalocyanine Sensitizers for Panchromatic Dye‐Sensitized Solar Cells

“…Dissymmetric squaraine structures are synthesized in a stepwise fashion from the reaction of dichlorocyclobutenedione with a slight excess of a nucleophilic molecule (shown as an electrophilic aromatic substitution in Scheme ). The corresponding product is then isolated and reacted with a second nucleophile to afford the final dissymmetric product . Symmetric squaraine dyes are easily synthesized in one step through the reaction of squaric acid and an appropriate nucleophile, such as a deprotonatable iminium derivative …”

“…This dye reaches an IPCE peak of 35 %; however, this performance is extraordinary given that only a few DSC dyes from any class produce electricity up to 1050 nm. A laterally anchored squaraine‐based dye (Sq 31) using an indoline donor has also been examined in DSC devices . Sq 31‐based devices demonstrated a broad absorption range (onset at 800 nm) with a peak IPCE response of 65 % (PCE of 3.5 %).…”

“…The corresponding product is then isolated and reactedw ith as econd nucleophile to afford the final dissymmetricp roduct. [14] Symmetric squaraine dyes are easily synthesized in one step throught he reaction of squaric acid and an appropriate nucleophile, such as ad eprotonatable iminium derivative. [15] Dyes based on metal-free chromophores, such as boron dipyrromethene (BODIPY) and diketopyrrolopyrrole (DPP), are frequentlyt argeted because of their innate NIR absorption features.…”

“…Al aterally anchored squaraine-based dye (Sq 31) using an indoline donor has also been examined in DSC devices. [14] Sq 31-based devices demonstrated ab road absorption range (onset at 800 nm) with ap eak IPCE response of 65 %( PCE of 3.5 %). The lateral anchora pproacho ffers as ynthetically convenient methodo f anchoring the dye to the TiO 2 surface for rapid dye synthesis.…”