New method boosts efficiency and longevity of organic solar cells

The Organic Electronics Research Group at Abo Akademi University collaborated with Professor Chang-Qi Ma's team at the Suzhou Institute for Nano-Tech and Nano-Bionics to achieve these results. Key contributors from Abo Akademi University include Ronald Osterbacka, Sebastian Wilken, and Oskar Sandberg.

The research highlights an exceptional efficiency of over 18% for structure-inverted solar cells with a 1 cm area. Additionally, these cells demonstrated a record-breaking lifespan of 24,700 hours under white light exposure, corresponding to a predicted operational life exceeding 16 years.

Organic photovoltaics (OPVs) are attractive for commercial applications due to their lightweight and flexible properties and energy-efficient manufacturing. Over the last five years, the power conversion efficiency of OPVs has surged, with conventional-structured cells surpassing 20% in laboratory conditions. However, materials used in these devices degrade when exposed to sunlight and air, limiting their long-term stability.

To enhance longevity, researchers advocate using the most robust material for the top contact layer. Structure-inverted, or n-i-p, solar cells provide greater durability, but their efficiency has lagged behind that of conventional designs. This new discovery addresses that gap, showing a clear route to improving both the performance and durability of these inverted solar cells.

The study identified a narrow recombination area caused by the bottom contact-typically made of metal oxides like zinc oxide-as a critical loss mechanism. By introducing a thin, solvent-processed silicon oxide nitrate (SiOxNy) passivation layer to the bottom contact, the researchers eliminated the recombination area. This innovation improved the photocurrent and overall efficiency of the solar cells. The findings suggest that this approach is viable for large-scale production of efficient and stable organic solar cells.

Research Report:Inverted organic solar cells with an in situ-derived SiOxNy passivation layer and power conversion efficiency exceeding 18%