ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Advanced materials (Deerfield Beach, Fla.), Jan 8, 2017
Corrosive precursors used for the preparation of organic-inorganic hybrid perovskite photoactive ... more Corrosive precursors used for the preparation of organic-inorganic hybrid perovskite photoactive layers prevent the application of ultrathin metal layers as semitransparent bottom electrodes in perovskite solar cells (PVSCs). This study introduces tin-oxide (SnOx ) grown by atomic layer deposition (ALD), whose outstanding permeation barrier properties enable the design of an indium-tin-oxide (ITO)-free semitransparent bottom electrode (SnOx /Ag or Cu/SnOx ), in which the metal is efficiently protected against corrosion. Simultaneously, SnOx functions as an electron extraction layer. We unravel the spontaneous formation of a PbI2 interfacial layer between SnOx and the CH3 NH3 PbI3 perovskite. An interface dipole between SnOx and this PbI2 layer is found, which depends on the oxidant (water, ozone, or oxygen plasma) used for the ALD growth of SnOx . An electron extraction barrier between perovskite and PbI2 is identified, which is the lowest in devices based on SnOx grown with ozone. ...
Elementary Processes in Organic Photovoltaics, 2016
Small-molecule π-systems bearing donor (D) and acceptor (A) groups constitute an interesting clas... more Small-molecule π-systems bearing donor (D) and acceptor (A) groups constitute an interesting class of dyes because of their tunable strong absorption, which covers the visible and near-infrared range. The dipolarity associated with D–A structures directs antiparallel stacking arrangements in the solid state, thus reducing the dipolar disorder at the supramolecular level. Their straightforward synthesis and purification make them good candidates for photovoltaic application with power conversion efficiencies >6 %. This review summarizes the application of D–A dyes, and in particular merocyanines, in organic photovoltaics in recent years.
Journal of the American Chemical Society, Jan 24, 2016
Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macro... more Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macromolecules, as they can allow the rapid generation of libraries of materials as a method to tune properties. MCRs could prove particularly useful in the synthesis of π-conjugated polymers in which structural changes are necessary for fine-tuning of electronic properties. We describe here the first metal-free multicomponent approach to conjugated polymers. This reaction exploits the coupling of imines, acid chlorides, and (catechyl)PPh to generate phospha-münchnone-containing polymers, which can be converted to poly(pyrroles) via cycloaddition. The platform allows for the efficient synthesis of families of high molecular weight polymers in one step from readily available monomers.
Nonlinear Optical Properties of Organic Materials VII, 1994
ABSTRACT Photorefractive (PR) polymers are a new class of PR materials in which large (approximat... more ABSTRACT Photorefractive (PR) polymers are a new class of PR materials in which large (approximately 10-3) photoinduced refractive index changes can be generated with very low light power density (approximately 100 mW/cm2 or less). They offer structural flexibility, ease of processing and lower cost compared with commonly used inorganic PR crystals. We have developed a PR polymer composite with significantly enhanced performance compared with the existing PR polymers: for the first time, complete diffraction of an incident beam into the first (Bragg) diffraction order was observed in a 105 micrometers thick layer of a PR polymer. Absorption and reflection losses limit the measured maximum diffraction efficiency to 86%. The material also exhibits a net two-beam coupling gain of more than 200 cm-1. These results show that this class of materials presents a good practical alternative to the inorganic PR crystals.
Summaries of Papers Presented at the Conference on Lasers and Electro Optics, Jun 2, 1996
Summary form only given. Using the variable-frequency ellipsometric technique, we measure the tot... more Summary form only given. Using the variable-frequency ellipsometric technique, we measure the total refractive index modulation as a function of the frequency of the applied electric field. From these measurements we deduce the relative contributions of the poling birefringence, the Pockels, and the Kerr effects. The experimental setup for the variable frequency ellipsometric technique is presented. We show experimental data for two high-diffraction efficiency photorefractive polymer composites, DMNPAA:PVK:ECZ:TNF and FDEANST:PVK:ECZ:TNF.
CLEO:2011 - Laser Applications to Photonic Applications, 2011
... gain medium [11]. In the present work, we have characterized long-range surface plasmon polar... more ... gain medium [11]. In the present work, we have characterized long-range surface plasmon polariton (LRSPP) planar waveguides consisting of a thin gold film adjacent to an optically pumped fluorescent polymer layer. For this ...
We have demostrated that oxetane-derivatized hole conductors as well as electroluminescent polyme... more We have demostrated that oxetane-derivatized hole conductors as well as electroluminescent polymers can be crosslinked via cationic ring-opening polymerisation (CROP) without deterioration of their electrical and electrooptical properties. This allows the fabrication of electronic multilayer devices via solution process. Here, we demonstrate three kinds of CROP crosslinking methods. They are (1) oxidative crosslinking, (2) photo crosslinking, and (3) trityl crosslinking. The crosslinking process parameters as well as the fluorescence characteristics and the solvent resistance of the resulting films have been investigated. The result shows that the oxidative crosslinking (1) gives the possibility to obtain the doping effect which increases the conductivity of the insoluble layer, although it reduces the fluorescence characteristics. The photo crosslinking (2) is controlled by irradiation; therefore, it gives the possibility to pixelate or pattern the film (lithography). It shows less fluorescence quenching than in (1). The trityl crosslinking (3) is suitable for the devices which are not pixelated and do not need the doping effect. Irradiation is not applicable here. Finally, we applied the insoluble layers in hole-only devices and blue-emitting OLEDs. We found that introduction of the layers improves the efficiency of the OLEDs.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Advanced materials (Deerfield Beach, Fla.), Jan 8, 2017
Corrosive precursors used for the preparation of organic-inorganic hybrid perovskite photoactive ... more Corrosive precursors used for the preparation of organic-inorganic hybrid perovskite photoactive layers prevent the application of ultrathin metal layers as semitransparent bottom electrodes in perovskite solar cells (PVSCs). This study introduces tin-oxide (SnOx ) grown by atomic layer deposition (ALD), whose outstanding permeation barrier properties enable the design of an indium-tin-oxide (ITO)-free semitransparent bottom electrode (SnOx /Ag or Cu/SnOx ), in which the metal is efficiently protected against corrosion. Simultaneously, SnOx functions as an electron extraction layer. We unravel the spontaneous formation of a PbI2 interfacial layer between SnOx and the CH3 NH3 PbI3 perovskite. An interface dipole between SnOx and this PbI2 layer is found, which depends on the oxidant (water, ozone, or oxygen plasma) used for the ALD growth of SnOx . An electron extraction barrier between perovskite and PbI2 is identified, which is the lowest in devices based on SnOx grown with ozone. ...
Elementary Processes in Organic Photovoltaics, 2016
Small-molecule π-systems bearing donor (D) and acceptor (A) groups constitute an interesting clas... more Small-molecule π-systems bearing donor (D) and acceptor (A) groups constitute an interesting class of dyes because of their tunable strong absorption, which covers the visible and near-infrared range. The dipolarity associated with D–A structures directs antiparallel stacking arrangements in the solid state, thus reducing the dipolar disorder at the supramolecular level. Their straightforward synthesis and purification make them good candidates for photovoltaic application with power conversion efficiencies >6 %. This review summarizes the application of D–A dyes, and in particular merocyanines, in organic photovoltaics in recent years.
Journal of the American Chemical Society, Jan 24, 2016
Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macro... more Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macromolecules, as they can allow the rapid generation of libraries of materials as a method to tune properties. MCRs could prove particularly useful in the synthesis of π-conjugated polymers in which structural changes are necessary for fine-tuning of electronic properties. We describe here the first metal-free multicomponent approach to conjugated polymers. This reaction exploits the coupling of imines, acid chlorides, and (catechyl)PPh to generate phospha-münchnone-containing polymers, which can be converted to poly(pyrroles) via cycloaddition. The platform allows for the efficient synthesis of families of high molecular weight polymers in one step from readily available monomers.
Nonlinear Optical Properties of Organic Materials VII, 1994
ABSTRACT Photorefractive (PR) polymers are a new class of PR materials in which large (approximat... more ABSTRACT Photorefractive (PR) polymers are a new class of PR materials in which large (approximately 10-3) photoinduced refractive index changes can be generated with very low light power density (approximately 100 mW/cm2 or less). They offer structural flexibility, ease of processing and lower cost compared with commonly used inorganic PR crystals. We have developed a PR polymer composite with significantly enhanced performance compared with the existing PR polymers: for the first time, complete diffraction of an incident beam into the first (Bragg) diffraction order was observed in a 105 micrometers thick layer of a PR polymer. Absorption and reflection losses limit the measured maximum diffraction efficiency to 86%. The material also exhibits a net two-beam coupling gain of more than 200 cm-1. These results show that this class of materials presents a good practical alternative to the inorganic PR crystals.
Summaries of Papers Presented at the Conference on Lasers and Electro Optics, Jun 2, 1996
Summary form only given. Using the variable-frequency ellipsometric technique, we measure the tot... more Summary form only given. Using the variable-frequency ellipsometric technique, we measure the total refractive index modulation as a function of the frequency of the applied electric field. From these measurements we deduce the relative contributions of the poling birefringence, the Pockels, and the Kerr effects. The experimental setup for the variable frequency ellipsometric technique is presented. We show experimental data for two high-diffraction efficiency photorefractive polymer composites, DMNPAA:PVK:ECZ:TNF and FDEANST:PVK:ECZ:TNF.
CLEO:2011 - Laser Applications to Photonic Applications, 2011
... gain medium [11]. In the present work, we have characterized long-range surface plasmon polar... more ... gain medium [11]. In the present work, we have characterized long-range surface plasmon polariton (LRSPP) planar waveguides consisting of a thin gold film adjacent to an optically pumped fluorescent polymer layer. For this ...
We have demostrated that oxetane-derivatized hole conductors as well as electroluminescent polyme... more We have demostrated that oxetane-derivatized hole conductors as well as electroluminescent polymers can be crosslinked via cationic ring-opening polymerisation (CROP) without deterioration of their electrical and electrooptical properties. This allows the fabrication of electronic multilayer devices via solution process. Here, we demonstrate three kinds of CROP crosslinking methods. They are (1) oxidative crosslinking, (2) photo crosslinking, and (3) trityl crosslinking. The crosslinking process parameters as well as the fluorescence characteristics and the solvent resistance of the resulting films have been investigated. The result shows that the oxidative crosslinking (1) gives the possibility to obtain the doping effect which increases the conductivity of the insoluble layer, although it reduces the fluorescence characteristics. The photo crosslinking (2) is controlled by irradiation; therefore, it gives the possibility to pixelate or pattern the film (lithography). It shows less fluorescence quenching than in (1). The trityl crosslinking (3) is suitable for the devices which are not pixelated and do not need the doping effect. Irradiation is not applicable here. Finally, we applied the insoluble layers in hole-only devices and blue-emitting OLEDs. We found that introduction of the layers improves the efficiency of the OLEDs.
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Papers by Klaus Meerholz