HKPU and Zhejiang University stabilize perovskite solar cells to 2,200 hours at 26.55% efficiency

Researchers from The Hong Kong Polytechnic University and Zhejiang University have identified a microscale degradation mechanism at crystal boundaries in polycrystalline perovskite solar cells, according to a study published in the journal Watt springer.comWattspringer.comOpen source ↗. By applying a targeted chemical treatment to passivate facet-specific defects, the team produced prototype solar cells that achieved a power conversion efficiency of 26.55% and maintained over 90% of their performance after more than 2,200 hours of continuous one-sun illumination.

Inter-grain defect mechanism

Polycrystalline perovskite films consist of microscopic grains with differing crystal facet orientations, such as (100) and (111). The researchers determined that hetero-facet grain boundaries induce an asymmetric inter-grain charge recombination pathway under illumination. Despite the superior intrinsic photostability of the (111) facet, formamidinium vacancy defects concentrated at the (111) side of these boundaries caused a non-equilibrium accumulation of photogenerated positive charge carriers, or holes. This localized imbalance accelerated photodegradation precisely at the hetero-facet interfaces.

Targeted defect passivation

To suppress this degradation route, the authors introduced 3-fluorophenylethylammonium bromide (m-F-PEABr) into the material. The compound targeted the identified formamidinium vacancies at the (111)-facet grain boundaries, effectively homogenizing carrier recombination across adjacent grains. In laboratory tests under continuous one-sun conditions, treated prototype cells reached a T90 operational lifetime exceeding 2,200 hours alongside the 26.55% efficiency mark. Further research is required to evaluate the performance of this interface stabilization strategy in large-area modules under fluctuating outdoor operating environments.