Publication date: 15th December 2025
The solubility of organic semiconductors and the miscibility between pairs are critical to understand and optimize the nanomorphology of bulk heterojunction (BHJ) active layers in organic photovoltaic (OPV) devices. These properties influence the formation of interpenetrating domains and the purity of phase-separated regions, fundamental for exciton dissociation, charge transport and recombination processes [1,2]. Existing methods for evaluating solubility rely on measuring the saturation solubility of the solid material in a range of solvents to obtain their Hansen Solubility Parameters (HSPs), requiring a large amount of material [3,4]. Miscibility is typically found by deriving the Flory-Huggins interaction parameter (χ) from surface energies (σ) obtained via contact angle measurements with pure solvents, using either the the Wu[5] or the Owens-Wendt-Rabel-Kaelble (OWRK)[6,7] model.
In this work, we propose a simple method based on contact angle measurements as an alternative to determine the HSPs, consisting of evaluating the wettability of good:bad solvent mixtures on thin films of pristine organic semiconductors. By gradually varying the solvent compositions from 1:0 to 0:1, contact angles are measured and a score is assigned to each by setting an angle threshold, indicating good or poor wetting on the film surface. These scores are recorded using the HSPiP software to extract the three solubility parameters: dispersive (δD), polar (δP), and hydrogen bonding (δH), by fitting a solubility sphere of the target material. Moreover, our proposed method allows to perform temperature-dependent measurements, which is of high relevance to predict morphological stability [2,8]. Then, the HSP values can be used to determine the χ parameter.
A set of state-of-the-art high-performing donor and acceptor materials is selected (donors: PM6, D18, PTQ10, PTQ11; acceptors: Y6, Y7, L8-BO, HU-Y6, DTY6 and o-IDTBR), alongside the benchmark donor P3HT and the fullerene acceptors PC60BM and PC70BM, to evaluate the applicability of the method. The resulting dataset library is complemented with temperature-dependent measurements on a subset list of materials (P3HT, PM6, PC60BM and Y6). Our results indicate that the approaches using surface energy values are highly sensitive to small variations in contact angle measurements, which can lead to great χ value deviations. In contrast, the HSP method shows a great robustness.
The proposed method greatly reduces material consumption (only 3 mg needed for each organic semiconductor) while offering a fast, simple, and robust route to obtain HSPs and χ values. The resulting parameters serve as quantitative descriptors for the rational selection of organic materials to achieve a favourable active layer morphology and to improve device efficiency and stability.
Keywords: solubility, organic photovoltaics, Hansen solubility parameters, miscibility, Flory–Huggins interaction parameter
This work is part of the European Programme EIFFEL, which has received funding from the Horizon Europe Framework Programme under the Marie Skłodowska-Curie Doctoral Networks Grant Agreement - GA-101119780, and the María de Maeztu Unit of Excellence Programme CEX2023-001300-M / funded by MICIU/AEI /10.13039/501100011033.
I.B.C. thanks MICINN for funding through the Ramón y Cajal fellowship, grant ref. RYC2022-035399-I. L.S. is grateful to MICINN Ramón y Cajal program for an individual fellowship grant agreement RYC2019-026704-I.
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.