Functional Molecular Liquids in Optoelectric Applications

Functional molecular liquids are solvent-free fluidic materials composed of small π-conjugated organic molecules endowed with optoelectronic function through tailored alkylation, supramolecular interactions or self-assembly. At ambient conditions these materials combine conformability, processability and high chromophore density, providing novel platforms for flexible displays, soft electrets, energy harvesters and tunable luminescent inks. Molecular design strategies focus on selecting conjugated cores and peripheral substituents to modulate viscosity, photophysical response, charge retention and intermolecular π–π interactions. Control over phase behaviour—including gelation and liquid-crystalline mesophases—enables precise tuning of mechanical modulus and emission characteristics. Recent progress has demonstrated solvent-free electroluminescent microfluidic devices, extendable colour tuning via dopants and robust mechano-electrical performance under deformation. The global significance of these liquids lies in their potential to underpin next-generation wearable electronics, foldable lighting and adaptive sensing technologies.

Research from Nature Portfolio

Recent studies have employed time-resolved spectroscopy on alkylated pyrene systems to elucidate and fine-tune local π–π interactions, enabling the design of liquids with adjustable photophysical and rheological characteristics. Solvent-free liquid porphyrins have been developed as stable, deformable electrets, exhibiting prolonged corona-charged states and efficient mechanoelectric conversion in stretchable devices under ambient conditions. Additionally, microfluidic integration of liquid organic semiconductors with quantum dots has yielded narrow-band, high-purity electroluminescence across red, green and blue channels, demonstrating the feasibility of liquid-based flexible microdisplays.

Functional Molecular Liquids in Optoelectric Applications publication trend

The graph below shows the total number of articles in functional molecular liquids in optoelectric applications across all publications each year (not limited to Nature Index journals).

Technical terms

Functional molecular liquid: A solvent-free fluid composed of small organic molecules bearing conjugated cores and peripheral substituents, combining fluidity with optoelectronic functionality.

π–π interactions: Non-covalent attractions between aromatic or conjugated systems that govern molecular aggregation, photophysical behaviour and charge transport.

Electret: A dielectric material that maintains a quasi-permanent electric field or surface charge, used for mechanoelectric energy conversion and sensing.

Excimer: A transient excited-state dimer formed by two identical molecules, yielding characteristic broad-band emission distinct from monomer fluorescence.

References

1. Alkyl–π Functional Molecular Gels: Control of Elastic Modulus and Improvement of Electret Performance. Angewandte Chemie International Edition (2024).
2. Responsive molecular liquid materials. Responsive Materials (2023).
3. A Guide to Design Functional Molecular Liquids with Tailorable Properties using Pyrene-Fluorescence as a Probe. Scientific Reports (2017).
4. Soft chromophore featured liquid porphyrins and their utilization toward liquid electret applications. Nature Communications (2019).
5. Liquid/solution-based microfluidic quantum dots light-emitting diodes for high-colour-purity light emission. Scientific Reports (2020).
6. Control of the Organization of 4,4′-bis(carbazole)-1,1′-biphenyl (CBP) Molecular Materials through Siloxane Functionalization. Molecules (2023).