Manuel Hamburger

Photocatalytic hydrogen evolution through fully conjugated poly(azomethine) networks

Three-dimensional conjugated poly(azomethine) networks were found to be promising candidates for applications in photocatalytic water splitting. Straightforward synthetic protocols lead to fully organic photocatalysts that showed enhanced long-time stability. Furthermore, the catalytic performance of these materials was correlated to the molecular composition and the optoelectronic properties of the samples.

The Compromises of Printing Organic Electronics: A Case Study of Gravure‐Printed Light‐Emitting Electrochemical Cells

Light-emitting electrochemical cells (LECs) are fabricated by gravure printing. The compromise between device performance and printing quality is correlated to the ink formulation and the printing process. It is shown that the rheological properties of the ink formulations of LECs can be tailored without changing the chemical composition of the material blend.

Soluble Diazaiptycenes: Materials for Solution-Processed Organic Electronics

The synthesis and characterization of soluble azaiptycenes is reported. Optical and physical properties were studied and compared with those of the structurally consanguine azaacenes. Electrochemical experiments and quantum-chemical calculations revealed the electronic structure of the iptycene derivatives. Their crystallization behavior was examined. A highly fluorescent amorphous diazatetracene derivative was integrated into a simple organic light-emitting diode, showing enhanced performance compared with that of previously reported, structurally similar tetracenes.

N-Fused quinoxalines and benzoquinoxalines as attractive emitters for organic light emitting diodes

We describe the modular synthesis of quinoxaline fluorophores exhibiting strong fluorescence over the whole visible spectrum. Based on their fluorescence quantum yield, frontier orbital energies and solid-state aggregation behavior, several compounds work well in fluorescent organic light emitting diodes (OLEDs) with luminances over 1000 cd m−2 at 8 V driving voltage.

Thiadiazoloquinoxalines: Tuning Physical Properties through Smart Synthesis

The synthesis of π-conjugated acceptors based on thiadiazoloquinoxaline (TQ) derivatives is described. Apart from reporting on the functionalization of the TQ core, the influence of the substituents was studied by UV-vis absorption and emission spectroscopy, cyclic voltammetry measurements, and DFT calculations. By changing the donor as well as the π-spacer, a fine-tuning of the photo- and electrochemical properties was achieved.

Light‐Induced Protein Dimerization by One‐ and Two‐Photon Activation of Gibberellic Acid Derivatives in Living Cells

We developed a highly efficient system for light-induced protein dimerization in live cells using photo-caged derivatives of the phytohormone gibberellic acid (GA3 ). We demonstrate the application of the photo-activatable chemical inducer of dimerization (CID) for the control of protein translocation with high spatiotemporal precision using light as an external trigger. Furthermore, we present a new two-photon (2P)-sensitive caging group, whose exceptionally high two-photon cross section allows the use of infrared light to efficiently unleash the active GA3 for inducing protein dimerization in living cells.

Electron-transporting phenazinothiadiazoles with engineered microstructure

Novel triisopropylsilyl-(TIPS)-alkynylated phenazinothiadiazoles were prepared by condensation of ortho-quinones and an alkynylated 5,6-diamino-2,1,3-benzothiadiazole. The targets show head-to-head dimerisation in the solid state, which, according to calculated transfer integrals should favor charge transport. The compounds form polycrystalline thin films when spin cast from solution. Two derivatives are attractive electron transporting materials with an average electron mobility μe in thin film transistors (TFT) of 0.07 cm2 V−1 s−1.

From thia- to selenadiazoles: changing interaction priority.

The synthesis, optical, and electrochemical properties as well as solid-state structures of a series of alkynylated, benzannulated selenadiazoles are reported. This set of compounds is compared to the lighter homologue series, the thiadiazoles. The selenadiazoles show head-to-head dimerization in the solid state, while packing of the thiadiazoles was dominated by the steric bulk of the side groups. The Se-N interaction is a supramolecular motif that should drive the effective self-assembly and modulate charge transport when these compounds are used as thin films in devices.

Light‐Induced Solubility Modulation of Polyfluorene To Enhance the Performance of OLEDs

Liquid-phase processing is a key prerequisite for the cost-efficient fabrication of organic electronic devices. We report an approach for light-induced modulation of the solubility of π-conjugated polymers (polyfluorene) with side chains functionalized with hydroxycinnamic acid. Irradiation with light cleaves the solubilizing side chains and renders the thin films of the polyfluorene insoluble. In a proof of concept device, polyfluorenes were applied as emissive layers in OLEDs. Photoirradiation of the emission layer leads to an increase in OLED performance combined with a modulation of the solubility of the thin film. These results offer the possibility for further development in terms of manipulating the solubility and emissive parameters of an important class of functional materials.

Impact of processing on the chemical and electronic properties of phenyl-C61-butyric acid methyl ester

For the comparison of solution-processed to evaporated materials in organic optoelectronic devices, phenyl-C61-butyric acid methyl ester (PCBM) has been claimed to be a suitable material. However, we ascertained differences between spin-coated and vacuum sublimed thin films. In this contribution, we thoroughly investigate the effects of thermal evaporation of PCBM in a strongly interdisciplinary approach, applying physical characterization techniques such as photoelectron (PES) and infrared (IR) spectroscopy in combination with further chemical analysis using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and ultra-performance liquid chromatography-coupled mass spectrometry (UPLC-MS), as well as proton nuclear magnetic resonance spectroscopy (1H-NMR). The methods were applied to thin films prepared by solution-based deposition techniques and by thermal evaporation. Additionally, comparison to an evaporated C60 film and the crucible residues is carried out. Changes in the IR spectrum of the PCBM films already indicate a change in the molecular structure of PCBM. The UPLC chromatogram of the redissolved organic film proves the formation of several molecular species, including bare C60. However, the effect of degradation on the electronic properties was found to be limited, as an almost unchanged ionization potential of 6.1 eV was determined with UPS for both the solution processed as well as the evaporated films. Also bulk-heterojunction (BHJ) solar cells fabricated using pure and thermally treated PCBM showed the same J–V characteristics under illumination.