Researchers from the Institute of Microelectronics of the Chinese Academy of Sciences and the North China Electric Power University developed an in situ epitaxial blocking structure on the wide-bandgap mixed-halide perovskite, which significantly suppressed the phase segregation of perovskite and improved the efficiencies of both single-junction and four-terminal solar cells.

This work was published in Joule on May 12, 2023.

Wide-bandgap mixed-halide perovskites show promise of realizing efficient tandem solar cells but at present suffer from photoinduced phase segregation, which deteriorates their device efficiency and stability.

The researchers implemented a highly crystalline blocking structure to control phase segregation by in situ epitaxial growth onto a mixed-halide wide-bandgap perovskite.

Due to the released lattice strain, improved potential barrier of halide ion migration, and reduced defects by the blocking structure, the mixed-halide perovskite solar cell with a bandgap of 1.65 eV demonstrated a remarkable open-circuit voltage of 1.25 V (maximum 1.26 V) with a champion efficiency of 21.80% (certified 21.52%). Under continuous 1-sun white LED illumination, the device stored in nitrogen glovebox retained 90% of initial efficiency after 1080 hours.

The semitransparent device using the transparent indium tin oxide (ITO) back electrode yielded a state-of-the-art certificated efficiency of 19.15%, and a four-terminal tandem device was constructed by overlaying it on a silicon solar cell, obtaining a high efficiency of 28.83%.

The work is of great significance for the development of perovskite-based tandem photovoltaics.