Heteroquinoid Merocyanine Dyes with High Thermal Stability as Absorber Materials in Vacuum‐Processed Organic Solar Cells

Abstract

A series of heteroquinoid merocyanine dyes with an extended π‐system as well as lower homologues (bearing varied donor units such as benzothiazolylidene and 4H‐pyran‐4‐ylidene) were synthesized, and their thermal, optical and electrochemical properties were investigated. The dyes exhibit a variety of features that are desirable for solar cell production. These include strong absorption coefficients (up to 67.000 L M–1 cm–1), broad Vis/NIR absorption bands, frontier molecular orbital energies suitable for electron transfer to C60, and electronic gaps ranging from 0.90 to 1.74 eV. Owing to their high thermal stability, the dyes can be sublimated in high yields. For three of the dyes, the packing arrangements in the solid state by single‐crystal X‐ray analysis were examined. The photovoltaic characteristics of the most promising thienoquinoid merocyanine dye was investigated in devices using C60 as acceptor material. In an optimized vacuum‐processed device, a PCE of 3.6 % was achieved.

4H-pyranylidene-based small push-pull chromophores: Synthesis, structure, electronic properties and photovoltaic evaluation

“…Hz, 1 H), 7.66 (dd, J1 = 4.2 Hz, J2 = 0.4 Hz, 1 H), 7.78 (br s, 1 H). 13 C-NMR (100 MHz, CD2Cl2): δ (ppm) 27. 9, 30.1, 75.6, 102.7, 105.4, 114.3, 115.1, 129.2, 134.2, 138.9, 139.9, 150.5, 156.7, 168.9 H).…”

“…9, 30.1, 75.6, 102.7, 105.4, 114.3, 115.1, 129.2, 134.2, 138.9, 139.9, 150.5, 156.7, 168.9 H). 13 C-NMR (100 MHz, CD2Cl2): δ (ppm) 28.1, 36. 5, 97.1, 102.8, 107.0, 112.9, 115.6, 128.4, 129.2, 129.4, 130.1, 132.6, 135.7, 136.5, 136.6, 143.7, 155.8, 162.3, 164.7, 167.…”

“…[12] However, to the best of our knowledge, the γ-pyranylidene moiety has never been used as electron-donating group D in small conjugated D-A molecules for photovoltaic application, although an heteroquinoid merocyanine dye derived from 2,6-diphenyl-4H-pyranylidene has been recently considered. [13] It is worth noting that a parent dipyran-based ladder-type building block has been recently used as central donating group D in A-D-A conjugated molecules for efficient non-fullerene acceptors in OPV. [14] On the other hand, the system 2,2',6,6'-tetraphenyldipyranylidene has been used as holetransporting material for hybride perovskite solar cells, [15] and as an efficient hole-collecting interfacial layer in organic solar cells based on poly(3-hexylthiophene):phenyl-C61-butyric acid methylester (P3HT:PCBM).…”

“…H), 5.91 (d, J = 2.2 Hz, 1 H), 6.70 (d, J = 2.2 Hz, 1 H), 6.71 (br s, 1 H), 6.90 (d, J = 4.2 Hz, 1 H), 6.92 (dd, J1 = 3.4 Hz, J2 = 1.3 Hz, 1 H), 7.0 (dd, J1 = 5.2 Hz, J2 = 3.4 Hz, 1H), 7.37 (dd, J1 = 5.2 Hz, J2 = 1.2 Hz, 1 H), 7.39 (d, J = 4.2 Hz, 1 H), 7.63-7.61 (m, 5 H) 13. C-NMR (100 MHz, CD2Cl2): δ (ppm) 28.…”

Triphenylamine-Merocyanine-Based D1-A1-π-A2/A3-D2 Chromophore System: Synthesis, Optoelectronic, and Theoretical Studies

“…They are attractive dyes for high technological applications such as nonlinear optics and photorefractive materials due to their polarizabilities and dipole moments [26,27,28,29]. Merocyanine dyes are also promising candidates for dye-sensitized solar cells (DSSCs) [30,31,32,33,34,35], photorefractive applications [36,37,38], and solution-processed BHJ OSCs [39,40]. Würthner and coworkers extensively investigated bulk heterojunction (BHJ) OSCs application of merocyanine dyes [41,42,43].…”