Design and synthesis of stable semiconductive hydrogen bonded organophosphonic acid frameworks (phosphonic acid-HOFs) for optoelectric applications (optoHOF)

• Applicants: Professor Dr. Jan Christoph Goldschmidt; Dr. Gündog Yücesan
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Solid State and Surface Chemistry, Material Synthesis
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 573314235

The project optoHOF aims to synthezize novel, thermally stable, microporous organic semiconductor thin films based on hydrogen-bonded organic frameworks (HOFs) and their implementation in optoelectronic components, specifically solar cells. These HOFs will be constructed using arylphosphonic acids incorporating carbazole, triphenylyne, and pyrene luminescent cores. We anticipate that hydrogen bonding patterns will align the luminescent cores within the crystal lattice, thereby inducing semiconducting behavior and optimizing optoelectronic properties. The inherent thermal and chemical stability of arylphosphonic acids is expected to yield sustainable and environmentally friendly thin film structures suitable for commercial optoelectronic applications. To further optimize surface area and optoelectronic properties of HOF crystals and their thin films, we plan to synthesize longer phenyl-tethered linkers via Suzuki-Cross coupling. Additionally, varying phosphonic acid protonation levels will be employed to enhance structural diversity and optimize optoelectronic properties of both HOF thin films and single crystals. BET methods will be used to characterize the surface area of the HOFs. Electrical and ionic conductivities of both HOF thin films and single crystals will be measured. To implement synthesized HOF materials in solar cells, precursor ink formulations will be developed, and the thin film formation and crystallization from liquid phase will be optimized. A comprehensive optoelectronic characterization of HOF powders and thin films will be carried out to assess charge carrier generation and recombination properties, comprising of band gap determination by UV-vis and photoluminescence (PL) spectroscopy, PL quantum yield (PLQY) , hyperspectral PL (hyPL) imaging, time resolved PL (trPL) decay measurements. Advanced film conductivity measurements will be carried out by light and temperature dependent photo-Hall and 4-point-probe measurements. HOF-based solar cells will be fabricated by incorporating HOF thin films in film stacks comprising of energy-band-aligned transparent charge extraction and suitable electrode layers. The performance of these HOF solar cells will be characterized by current-voltage measurements under simulate sunlight (AM1.5g). To quantify loss mechanisms, charge carrier recombination, transport and extraction dynamics will be analyzed by PLQY, hyPL, and trPL.

• DFG Programme: Research Grants