Researchers at Åbo Akademi University have improved the efficiency and durability of organic solar cells by eliminating a previously unknown loss mechanism. This breakthrough advances the commercialization of lightweight, flexible, and energy-efficient organic photovoltaics.
Efficiency and Longevity: Key Developments in Organic Solar Cells
Researchers at Åbo Akademi University have made a significant breakthrough in advancing organic solar cells by resolving a previously unknown loss mechanism. This innovation has enhanced both the efficiency and durability of these cells, thereby setting the stage for the broader commercialization of organic photovoltaics.
Organic solar cells, renowned for their lightweight, flexible design and energy-efficient production, have seen rapid advancements in efficiency over the past five years. Conventional designs now achieve power conversion efficiencies surpassing 18%, with some exceeding 20% in laboratory tests. However, the materials used in these cells remain vulnerable to sunlight and air exposure, which limits their long-term stability.
Researchers tackled these challenges by creating a structure-inverted design for organic solar cells. This innovation achieved a remarkable 18% efficiency and set a new record for the longest reported lifespan in the field. The study demonstrated a lifespan of 24,700 hours under white light illumination, equivalent to over 16 years of operational life.
These findings establish a new standard for organic photovoltaics, thus offering a sustainable and practical energy solution for the future. By combining improved efficiency with enhanced longevity, this breakthrough represents a significant step toward making organic solar cells commercially viable.
Innovations in Structure-Inverted Solar Cells
One key finding involves the structure-inverted, or n-i-p, solar cells. These cells feature a durable top contact layer, which makes them more stable than conventional designs. However, their power conversion efficiency has historically been lower. Researchers at Åbo Akademi University tackled this challenge by identifying and addressing a loss mechanism caused by the bottom contact layer.
The bottom contact — made from metal oxides like zinc oxide — creates a narrow recombination area that reduces photocurrent. To overcome this issue, the team introduced a thin silicon oxide nitrate (SiOxNy) passivation layer. This layer, when applied through a solvent process, eliminates the recombination area, which leads to significant efficiency improvements.
The Organic Electronics Research Group at Åbo Akademi University conducted the study in collaboration with Professor Chang-Qi Ma’s group at the Suzhou Institute for Nano-Tech and Nano-Bionics. Key researchers included Ronald Österbacka, Sebastian Wilken, Oskar Sandberg, amongst others. Their work highlights the new method's potential for large-scale production of efficient and stable organic solar cells.
The researchers used an innovative approach to enhance performance in structure-inverted solar cells. They developed an in situ-derived inorganic SiOxNy passivation layer, formed by curing a perhydropolysilazane thin film in ambient conditions. This layer addressed defects in the ZnO transport layer, which had previously caused losses in photocurrent due to recombination of photogenerated holes.
Practical Implications of the Discovery
The optimized SiOxNy interlayer not only passivates surface defects, but it also induces a preferential accumulation of non-fullerene acceptors near the electron contact. This arrangement enhances charge extraction and overall efficiency. The results showed certified power conversion efficiencies of 18.49% for smaller cells and 18.06% for larger cells. These efficiencies are among the highest reported for structure-inverted organic solar cells.
Moreover, the study revealed an estimated T80 lifetime of 24,700 hours, meaning the cells maintained 80% of their initial efficiency after this time under white light illumination. This corresponds to an operational lifespan exceeding 16 years, a crucial factor for practical applications.
The findings underscore the potential of organic solar cells for large-scale applications. Their lightweight and flexible design — combined with energy-efficient manufacturing processes — makes them attractive for commercialization. However, long-term stability has been a hurdle for widespread adoption. The new approach developed by Åbo Akademi University offers a solution to this challenge, thereby paving the way for more durable and efficient organic photovoltaics.
The research also highlights the importance of collaboration in advancing solar technology. By combining expertise in organic electronics and nanotechnology, the team has achieved results that could transform the renewable energy sector.