Efficient and stable panchromatic squaraine dyes for dye-sensitized solar cells

Abstract

A new series of stable, unsymmetrical squaraine near-IR sensitizers (JK-216 and JK-217), which are assembled using both thiophenyl pyrrolyl and indolium groups, exhibit a panchromatic light harvesting up to 780 nm. The JK-216 based cell exhibited a record efficiency of 6.29% for near-IR DSSCs. In addition, the JK-217 device showed an excellent stability under a light soaking test at 60 °C for 1000 h.

A High‐Efficiency Panchromatic Squaraine Sensitizer for Dye‐Sensitized Solar Cells

“…[5] More recently, a PCE of 6.29 % has been obtained using a more markedly unsymmetrical mixed pyrrole/indoline squaraine that also exhibits a red-shift of its main absorption peak relative to that of SQ1. [6] This previous work has demonstrated the efficacy of an unsymmetrical design for electron injection and of increased p conjugation to bathochromically shift the main low-energy absorption band; [5,6] however, the possibility that higher-energy absorption bands in squaraines can also contribute to the photocurrent in DSCs has only recently been investigated.…”

A High‐Efficiency Panchromatic Squaraine Sensitizer for Dye‐Sensitized Solar Cells

“…[5] More recently, a PCE of 6.29 % has been obtained using a more markedly unsymmetrical mixed pyrrole/indoline squaraine that also exhibits a red-shift of its main absorption peak relative to that of SQ1. [6] This previous work has demonstrated the efficacy of an unsymmetrical design for electron injection and of increased p conjugation to bathochromically shift the main low-energy absorption band; [5,6] however, the possibility that higher-energy absorption bands in squaraines can also contribute to the photocurrent in DSCs has only recently been investigated. [7] Herein we report the synthesis and optical, electronic, and photovoltaic properties of the unsymmetrical bis(indoline) squaraine sensitizer YR6 (Scheme 1), which incorporates more extended conjugation beyond the squaraine core than SQ1, as well as the more strongly p-accepting carboxycyanovinyl group as a surface-anchoring group instead of a directly attached carboxylic acid.…”

Pyrrolyl Squaraines–Fifty Golden Years

“…However, pyrrolyl squaraine dyes have undergone cyclic voltammograms to measure their redox chemistry [23,33,39,49,51,53,57,63,68] as have pyrrole-derived poysquaraines [30,41,49,50,54]. It is also worth noting that current density verses voltage (or J-V) curves have been measured, particularly on organic photovoltaics containing pyrrolyl squaraines [35,45,48,51,67]. Whang et al have recently focused on the preparation of free-standing flexible films of type III pyrrole-derived polysquaraines with electrical conductivities down to ~10 −5 S/cm [56,61].…”

“…Although this two-step polysquaraine synthetic procedure has not been widely adopted, the majority of polysquaraines derived from pyrrole from this paper onwards were of the Ajayaghosh and Eldo type III in their molecular structure (i.e., divinylbenzene bridged bispyrroles). Additionally increasing throughout this period of time was the synthesis of unsymmetrical pyrrole squaraine dyes [19,39,48,53,57,69,70]. Although a synthetic route to the pyrrole half-squaraine, semisquaraine, or emisquaraine (the necessary precursor to an unsymmetrical pyrrole squaraine dye), was first proposed in 1968 [3], more efficient (and safer) routes have been developed in recent times (refer to [82] for a good description and schematics).…”

“…One reason for doing this was the inclusion of pyrrolyl squaraines in the development of organic solar cells [30,31,41,48,51,53,54,57,63,69], or similarly for organic photovolatics [35,38,45,50,64,67]. It has also been possible that the some pyrrole-derived polysquaraines, such as that derived from pyrrole itself, can be used as black colour materials in toners and inks just because they are produced as black intractable powders [40].…”