Pseudo-planar heterojunction organic solar cell achieves world record efficiency of 20.21%

Chinese researchers have achieved a world-record efficiency of 20.21% in a pseudo-planar heterojunction organic solar cell, using a novel interfacial buffering layer to enhance device stability and performance. This breakthrough could significantly impact the development of scalable, high-efficiency organic photovoltaics.

The research team introduced a highly crystalline polymer, D18, as an interfacial buffer layer between donor and acceptor materials in the solar cell. This buffer layer minimizes solvent-induced swelling during fabrication, preserving the integrity of the active layer and enabling more controlled phase separation.

The optimized device, which incorporated a non-fullerene acceptor BTP-eC9 alongside the buffer layer, achieved a power conversion efficiency of 20.21%, surpassing previous records for this class of organic solar cells. The structure used includes layers of PM6 donor, D18 buffer, L8-BO acceptor, and additional electron transport layers, all assembled via layer-by-layer deposition, similar to the materials used in cutting-edge solar modules.

The researchers reported improvements in exciton generation, charge transport, and reduced recombination, attributing these to the enhanced morphology and interface stability provided by the buffer layer. The approach offers a practical pathway toward scalable manufacturing of high-performance organic solar cells.

Implications for Organic Photovoltaic Technology

This achievement demonstrates a viable method to push the efficiency limits of organic solar cells, which are valued for their lightweight, flexible, and potentially low-cost manufacturing. The use of a buffer layer to control morphology and stability could accelerate commercialization and widespread adoption of organic photovoltaics, especially in applications requiring lightweight or flexible modules.

By reaching over 20% efficiency, this development narrows the gap with inorganic photovoltaic technologies, potentially transforming the renewable energy landscape and expanding the use of organic solar cells in building-integrated and portable energy solutions.

Advances in Organic Solar Cell Design

Organic solar cells have historically lagged behind inorganic counterparts in efficiency, with typical values below 15%. Recent research has focused on improving morphology, stability, and charge transport through novel material combinations and device architectures, similar to efforts seen in advanced solar cell research.

Prior efforts to enhance efficiency involved blending donor and acceptor materials or modifying interfaces, but solvent-induced erosion during fabrication has limited reproducibility and stability. The introduction of buffer layers has been suggested but not widely implemented at this efficiency level until now.

This latest work builds on these efforts by demonstrating a scalable, layer-by-layer approach that maintains morphology control and achieves record efficiency in pseudo-planar heterojunction structures.

“The interfacial buffering strategy significantly improves the morphology and stability of the active layer, enabling higher efficiencies and better reproducibility.”

— an anonymous researcher

Remaining Challenges for Commercial Adoption

While the efficiency record is promising, it is still unclear how these devices perform under long-term operational conditions and in large-scale manufacturing environments. Stability testing over extended periods and under real-world conditions is ongoing, and scalability of the buffer layer process remains to be validated.

Further research is needed to confirm whether this approach can be reliably reproduced at industrial scales and whether the materials used are cost-effective for mass production.

Next Steps for Validation and Scaling Up

The research team plans to conduct extended stability testing and explore scalability of the buffer layer deposition process. They will also investigate the integration of this design into flexible and large-area modules to assess commercial viability. Peer review and independent replication of the results are expected to follow publication.

Industry stakeholders and manufacturers will monitor these developments closely as they evaluate the potential for commercial organic solar panels with efficiencies exceeding 20%.

Key Questions

What is a pseudo-planar heterojunction organic solar cell?

This is a type of organic photovoltaic device that combines features of planar and bulk heterojunction structures, aiming to optimize charge separation and transport within a well-defined interface.

How does the interfacial buffering layer improve efficiency?

The buffer layer prevents solvent erosion during fabrication, maintains active layer morphology, reduces recombination, and facilitates better charge transfer, leading to higher efficiency.

Is this technology ready for commercial use?

While the efficiency achievement is significant, further testing on device stability, scalability, and manufacturing processes is needed before commercial deployment.

What materials are used in this new solar cell design?

The device incorporates donor polymer PM6, a crystalline polymer D18 as the buffer layer, non-fullerene acceptor BTP-eC9, and other layers for charge transport, assembled via layer-by-layer deposition.

What are the main advantages of organic solar cells over inorganic ones?

Organic solar cells are lightweight, flexible, potentially lower-cost, and can be produced in large areas with roll-to-roll manufacturing, making them suitable for diverse applications.

Source: PV Magazine