Fullerene Derivatives in Organic Photovoltaic Devices

Fullerene derivatives have played a central role as electron acceptor materials in organic photovoltaic devices for over two decades, owing to their exceptional electron affinity, isotropic charge transport and solution processability. Chemical functionalisation of the fullerene cage enables precise tuning of frontier molecular orbitals, morphology and miscibility with donor polymers, which in turn dictates open-circuit voltage, short-circuit current density and fill factor. Tailored adducts such as phenyl-C61-butyric acid methyl ester (PCBM), bis-adducts and higher adducts offer deeper or shallower lowest unoccupied molecular orbital levels for optimised energy alignment. Advances in synthetic methods have improved yields and purity of key acceptors, while morphological control in bulk heterojunction blends has led to enhanced charge separation and reduced recombination. Recent trends emphasise the balance between molecular symmetry and crystallinity, multicomponent and ternary blends to stabilise device performance, and regaining interest in fullerenes as stabilising additives in non-fullerene systems. The global significance of this research is reflected in the drive towards low-cost, flexible and scalable solar technologies with improved operational stability.

Research from Nature Portfolio

Recent studies have demonstrated that alternative fullerene derivatives can raise the open-circuit voltage without compromising charge generation. One work introduced a bis-functionalised indene-fused C60 derivative that elevates the lowest unoccupied molecular orbital by over 140 mV compared with standard PCBM, leading to a measurable boost in power conversion efficiency in small-molecule solar cells. Another seminal contribution detailed an innovative manganese-promoted cycloaddition method to synthesise a wide range of mono- and biscycloadducts in high yield under mild conditions, enabling scalable access to high-performance acceptors such as PC61BM and beyond.

Fullerene Derivatives in Organic Photovoltaic Devices publication trend

The graph below shows the total number of articles in fullerene derivatives in organic photovoltaic devices across all publications each year (not limited to Nature Index journals).

Technical terms

Fullerene derivative: Chemical modification of a spherical carbon cage to tailor electronic, optical and morphological properties for use as electron acceptor materials in organic solar cells.

Bulk heterojunction: An interpenetrating network of donor and acceptor materials in the active layer of organic solar cells that maximises interface area for exciton dissociation and charge transport.

HOMO/LUMO: Acronyms for highest occupied and lowest unoccupied molecular orbitals; energy levels that govern electron donation and acceptance, respectively.

Open-circuit voltage: The maximum voltage attainable from a photovoltaic device under illumination when no external current is drawn, determined by the energy difference between donor HOMO and acceptor LUMO.

Power conversion efficiency: The ratio of the electrical power output of a solar cell to the incident light power, serving as a primary metric of device performance.

Bis-adduct isomer: One of several structural variants formed by covalent addition of two functional groups to the fullerene core, affecting energy levels, crystallinity and charge transport.

References

1. Structure–Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl‑C61 Butyric Acid Methyl Ester. Chemistry of Materials (2023).
2. A Review on Fullerene Derivatives with Reduced Electron Affinity as Acceptor Materials for Organic Solar Cells. Energies (2023).
3. Recent Developments in the Optimization of the Bulk Heterojunction Morphology of Polymer: Fullerene Solar Cells. Materials (2018).
4. Understanding the correlation and balance between the miscibility and optoelectronic properties of polymer–fullerene solar cells. Journal of Materials Chemistry A (2017).
5. Increased Efficiency in Small Molecule Organic Solar Cells Through the Use of a 56-π Electron Acceptor – Methano Indene Fullerene. Scientific Reports (2015).
6. Mono- and Di-Pyrene [60]Fullerene and [70]Fullerene Derivatives as Potential Components for Photovoltaic Devices. Molecules (2021).
7. Manganese powder promoted highly efficient and selective synthesis of fullerene mono- and biscycloadducts at room temperature. Scientific Reports (2015).