TY  - JOUR
A1  - Kim, Jin Hong
A1  - Liess, Andreas
A1  - Stolte, Matthias
A1  - Krause, Ana-Maria
A1  - Stepanenko, Vladimir
A1  - Zhong, Chuwei
A1  - Bialas, David
A1  - Spano, Frank
A1  - Würthner, Frank
T1  - An Efficient Narrowband Near-Infrared at 1040 nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye
JF  - Advanced Materials
N2  - A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC\(_{61}\)BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm\(^{-1}\)) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.
KW  - squaraine dyes
KW  - crystal engineering
KW  - J-aggregates
KW  - near-infrared sensitivity
KW  - organic photodiodes
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256374
VL  - 33
IS  - 26
ER  - 
TY  - JOUR
A1  - Renner, Rebecca
A1  - Mahlmeister, Bernhard
A1  - Anhalt, Olga
A1  - Stolte, Matthias
A1  - Würthner, Frank
T1  - Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area
JF  - Chemistry - A European Journal
N2  - A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol\(^{−1}\) for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol\(^{−1}\). The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.
KW  - Suzuki coupling
KW  - perylenebisimide dyes
KW  - circular polarized luminescence
KW  - chirality
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-249070
VL  - 27
IS  - 46
SP  - 11997
EP  - 12006
ER  - 
TY  - JOUR
A1  - Schembri, Tim
A1  - Kim, Jin Hong
A1  - Liess, Andreas
A1  - Stepanenko, Vladimir
A1  - Stolte, Matthias
A1  - Würthner, Frank
T1  - Semitransparent Layers of Social Self‐Sorting Merocyanine Dyes for Ultranarrow Bandwidth Organic Photodiodes
JF  - Advanced Optical Materials
N2  - Two dipolar merocyanines consisting of the same π‐conjugated chromophore but different alkyl substituents adopt very different packing arrangements in their respective solid state with either H‐ or J‐type exciton coupling, leading to ultranarrow absorption bands at 477 and 750 nm, respectively, due to exchange narrowing. The social self‐sorting behavior of these push‐pull chromophores in their mixed thin films is evaluated and the impact on morphology as well as opto‐electronical properties is determined. The implementation of this well‐tuned two‐component material with tailored optical features allows to optimize planar heterojunction organic photodiodes with fullerene ​(C\(_{60}\)) with either dual or single wavelength selectivity in the blue and NIR spectral range with ultranarrow bandwidths of only 11 nm (200 cm\(^{-1}\)) and an external quantum efficiency of up to 18% at 754 nm under 0 V bias. The application of these photodiodes as low‐power consuming heart rate monitors is demonstrated by a reflectance‐mode photoplethysmography (PPG) sensor.
KW  - exciton coupling
KW  - merocyanine dyes/pigments
KW  - narrow bandwidth
KW  - organic photodiodes
KW  - social self‐sorting
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-244762
VL  - 9
IS  - 15
ER  -