Tandem Organic Solar Cell Technologies

Tandem organic solar cells employ two or more stacked photoactive sub-cells, each tailored to absorb distinct regions of the solar spectrum, in order to exceed the efficiency limits of single-junction devices. By combining wide-bandgap front sub-cells with narrow-bandgap rear sub-cells, these architectures harvest visible and near-infrared photons more effectively, boosting overall power conversion efficiency. Key challenges include balancing photocurrents between series-connected sub-cells, minimising non-radiative voltage losses and engineering transparent, conductive interconnecting layers without compromising optical transmission. Molecular design strategies—such as heteroatom substitution and extended π-conjugation—have yielded acceptors with suppressed triplet exciton formation and deep infrared absorption. Concurrent advances in interface engineering, thickness optimisation and series–parallel interconnection schemes have relaxed material selection constraints and improved device stability. The global significance of these developments spans from large-area flexible panels to integrated solar-fuel systems, pointing towards scalable, low-cost production of high-efficiency organic photovoltaics.

Research from Nature Portfolio

Recent studies have designed ultra-narrow bandgap acceptors by heteroatom substitution, yielding rear sub-cells that absorb deep into the near-infrared while suppressing non-radiative triplet exciton formation, leading to monolithic tandem devices surpassing 19% power conversion efficiency. Another approach extended molecular conjugation in acceptor materials to broaden infrared absorption, enabling tandem configurations to achieve efficiencies above 16% with improved photostability. Foundational work has also introduced a series–parallel triple-junction architecture that relaxes current-matching constraints through combined interconnections, demonstrating printed organic and hybrid cells with high fill factors and minimal resistive losses.

Tandem Organic Solar Cell Technologies publication trend

The graph below shows the total number of articles in tandem organic solar cell technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Tandem organic solar cell: A photovoltaic device comprising two or more organic sub-cells stacked to harvest a broader spectrum of sunlight and enhance overall energy conversion.

Sub-cell: An individual photovoltaic unit within a tandem architecture, each designed with distinct absorption characteristics.

Narrow bandgap acceptor: An organic molecule engineered to absorb lower-energy (near-infrared) photons and reduce electronic energy losses.

Triplet exciton: A non-emissive excited state in an organic semiconductor where electron spins are parallel, often leading to non-radiative voltage loss.

Interconnecting layer: A conductive, transparent intermediary that electrically connects sub-cells and facilitates charge recombination with minimal optical losses.

Power conversion efficiency: The ratio of the electrical power output of a solar cell to the incident solar power input under standard conditions.

References

1. Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells. Nature Communications (2023).
2. High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor. Nature Communications (2021).
3. A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells. Nature Communications (2015).
4. A Cross‐Linked Interconnecting Layer Enabling Reliable and Reproducible Solution‐Processing of Organic Tandem Solar Cells. Advanced Energy Materials (2020).
5. Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells. Carbon Energy (2019).
6. Thickness Optimization of Thin-Film Tandem Organic Solar Cell. Micromachines (2021).