Judicious Design of Indoline Chromophores for High-Efficiency Iodine-Free Dye-Sensitized Solar Cells

Abstract

Indoline photosensitizers exhibit impressive short-circuit photocurrent but generally low molar extinction coefficient and rapid charge recombination, which limits their application in thin-film dye-sensitizerd solar cells (DSCs). Here, we incorporate a new dithieno[3,2-b:2',3'-d]pyrrole (DTP) segment (i.e., dihexyloxy-triphenylamine (DHO-TPA) substituted DTP) as the conjugated π-linker to construct a series of high molar absorption coefficient indoline dyes (XW69, XW70, and XW71) for DSCs employing a cobalt(II/III) redox electrolyte. Interestingly, this DTP linker is demonstrated as an efficient building block, not only slowing down the kinetics of charge recombination of titania electrons with tris(1,10-phenanthroline)cobalt(III) ions but also making a great contribution to the light absorption properties in comparison with the dihexylaniline substituted DTP. With respect to the dihexyloxy-triphenylamine dye (XW68), these new indoline dyes exhibit stronger light-harvesting and thus better power conversion efficiency of DSCs made from thin titania films. Benefitting from the bulky rigidity of the donor and π-conjugation unit, the XW70 dye displays a promising conversion efficiency as high as 8.78%, with a short-circuit current density (J(SC)) of 13.3 mA cm(-2), open-circuit voltage (V(OC)) of 943 mV, and fill factor (FF) of 0.70 under AM 1.5 illumination (100 mW cm(-2)). Furthermore, the effect of light irradiation on these dyes adsorbed on nanocrystalline TiO2 films was investigated, proving the photostability of these indoline chromophores. Our work has valued the feasibility of judicious design of indoline chromophores to obtain organic photosensitizers for high-efficiency iodine-free DSCs made from thin titania films.

The Hagfeldt Donor and Use of Next‐Generation Bulky Donor Designs in Dye‐Sensitized Solar Cells

“…Importantly, this strategy has shown widespread applicability regardless of the dye π‐bridge structure with thiophene and thiophene derivative‐based dyes ( W10 , JK‐314 , MA45 , LP227 , AH7 , TK6 , XW70 , QX02 , SGT‐103 , AP16 ), quinoxaline‐derived dyes ( YA422 , S3 , DT‐1 , FNE53 ), benzothiadiazole‐based dyes ( RR9 , C275 , C281 , ZL003 ), diketopyrrolopyrrole‐based dyes ( DPP17 ), and porphyrin‐based dyes ( XW51 , SGT‐021 , 2,4‐ZnP‐CN‐COOH ), which are all used to generate relatively low‐recombination‐rate systems (Figure ). The most common approach used is the incorporation of aryl alkyl ether groups where the aryl is benzene (16 examples in Figure ).…”

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

“…This may be due to the thiophene unit which increases the donor strength of the heterocyclic segments due to the delocalization of the contributing molecular orbitals and render a planar bridge comprising thiophene and Fl-DTP. Electron rich planar conjugation pathway is beneficial for the donor-acceptor interactions and lead to red-shift in the charge transfer transition [64]. The diphenylaminofluorene based dye 5c exhibited red-shifted absorption and enhanced molar extinction coefficient when compared to its congener dye 5b containing phenylene linker.…”

Ferrocene Derivatives Functionalized with Donor/Acceptor (Hetero)Aromatic Substituents: Tuning of Redox Properties

“…A way to limit this resides in the proper design of the dye. The choice of a sensitizer with hydrophobic chains resulted the key to improve the cell performances [20,[25][26][27][28]. A record efficiency was reached by using a porphyrin dye and a Co-polypyridyl electrolyte [6].…”