Near-infrared absorbing heterocyclic quinoid donors for organic solar cell devices

Abstract

New heterocyclic quinoid donor molecules were designed and synthesized for application to organic solar cells in the near-infrared region. Devices using one of these quinoid molecules as a photoexcitable donor and C 60 as an acceptor function in the visible and the near-infrared regions up to 890 nm. † Dedicated to Professor Max Malacria on the occasion of his 65th birthday. ‡ Electronic supplementary information (ESI) available: Experimental details, compound characterization, TG-DTA data, CV data, PYS data and other materials. See

Impact of Heterocycle Annulation on NIR Absorbance in Quinoid Thioacene Derivatives

“…UV/vis spectroscopy clearly shows the presence of an intense absorption band in the NIR region for all seven quinoid molecules (Figure 1c and d). In accordance with literature reports, we observed for 6 a broad absorption at 688 nm (1.80 eV) with large molar absorption coefficient (log ϵ =4.96) [12a] . Interestingly, the benzo derivative 4 exhibits similar absorption properties ( λ max =678 nm (1.83 eV), log ϵ =4.95), indicating that the NIR‐absorption is only marginally influenced by the nature of the central acene moiety.…”

“…Despite the significant interest in benzo‐derived quinoids, [10,11] the synthesis and characterisation of the p ‐methoxyphenyl derivative 4 has only been rudimentary described [10b] . However, 4 is readily synthesed by a Debus‐Radziszewski reaction [12a,15] of terephthalaldehyde ( 10 ) with p ‐anisil ( 11 ) in 83 % yield, followed by oxidation of the bisimidazole intermediate 12 with ferrous cyanide in 74 % yield. The latter reaction was accompanied by a dramatic colour change from pale yellow to deep blue (for UV/vis spectra, see below).…”

“…Furthermore, C5−C6 is about 0.1 Å shorter in 12 than in 4 , whereas the shorter bond lengths N1−C5 and N2−C6 in 4 account for localised double bonds. The quinoid 6 was synthesised in two steps from 13 according to the method described by Nakamura (Scheme 2b) [12a] and was adapted for the straightforward synthesis of the corresponding thieno[3,2‐ b ]thiophene derivative 7 from 15 (Scheme 2c). The reaction of the bisaldehyde 13 with p ‐anisil ( 11 ) in the presence of ammonium acetate provided 14 in 43 % yield.…”

Near‐Infrared‐Absorbing and Dopant‐Free Heterocyclic Quinoid‐Based Hole‐Transporting Materials for Efficient Perovskite Solar Cells

“…Aromatic quinoids with two 1,4‐diazacyclopentadien‐2‐ylidene terminals have several interesting features: (1) they are readily available and thermally stable, (2) they have a relatively planar core favoring intermolecular electronic coupling, and (3) they have intense absorption in the long wavelength region . It is also interesting to note that some hetero‐aromatic quinoids were used as p‐type materials for organic solar cells . We thus developed HTMs derived from 3,6‐di(2 H ‐imidazol‐2‐ylidene)cyclohexa‐1,4‐diene (DIQ), and two derivatives were synthesized (DIQ‐C6 and DIQ‐C12, Figure ).…”

“…Scheme illustrates the synthetic protocols for DIQ‐C6 and DIQ‐C12, and experimental details are given in the Supporting Information. The intermediate, DIP, was synthesized from terephthalaldehyde and 1,2‐bis(4‐alkyloxyphenyl)ethane‐1,2‐dione without purification by column chromatography . After oxidation of DIP with K 3 [Fe(CN) 6 ], DIQ‐C6 and DIQ‐C12 were obtained with a total yield ∼70 %.…”