Buried-Interface Iodine Redox Regulation for Durable All-Perovskite Tandem Photovoltaics

Area of Science:

• Materials Science
• Chemical Engineering
• Renewable Energy

Background:

• Tin-lead (Sn-Pb) mixed perovskites are key to high-efficiency all-perovskite tandem solar cells (APTSCs).
• Buried-interface instability, particularly I⁻ oxidation and I₂ diffusion within PEDOT:PSS, limits APTSC commercialization.
• A fundamental chemical degradation pathway involving iodine species remains unresolved.

Purpose of the Study:

• To address the buried-interface instability in Sn-Pb mixed perovskite solar cells.
• To introduce a novel additive, 6-amino-2-thiouracil (ATU), to mitigate iodine-related degradation.
• To enhance the efficiency and long-term stability of all-perovskite tandem solar cells (APTSCs).

Main Methods:

• Incorporation of 6-amino-2-thiouracil (ATU) into the PEDOT:PSS layer of APTSCs.
• Investigating the chemical interaction between ATU and PSS to alleviate I⁻ oxidation.
• Utilizing the C═S moiety of ATU to reduce I₂ back to I⁻, establishing an iodine-recycling mechanism.
• Concurrent defect passivation and crystallization modulation of perovskite films.

Main Results:

• Optimized APTSCs achieved a champion efficiency of 29.29% (certified 28.79%).
• The ATU additive established a dynamic iodine-recycling mechanism, targeting corrosive I₂.
• Devices maintained over 85% of initial efficiency after 500 hours of maximum power point tracking, demonstrating improved stability.

Conclusions:

• 6-amino-2-thiouracil (ATU) effectively targets and resolves the buried-interface instability caused by iodine species in APTSCs.
• The developed iodine-recycling mechanism provides a new strategy for durable perovskite photovoltaics beyond conventional passivation.
• This work offers a rational framework for enhancing the commercial viability of high-efficiency perovskite solar cells.