Continuously graded-doped SnO₂ for efficient n-i-p perovskite solar cells

Area of Science:

• Materials Science
• Energy Science
• Physical Chemistry

Background:

• Conventional n-i-p perovskite solar cells (PSCs) show stagnated efficiency (~26%) compared to p-i-n architectures.
• Non-radiative recombination at the electron transport layer (ETL)/perovskite interface is a key bottleneck.
• The physical origin of these recombination losses, linked to band misalignment and electron accumulation, was previously unclear.

Purpose of the Study:

• To elucidate the physical origin of recombination losses at the ETL/perovskite interface in n-i-p PSCs.
• To engineer a novel ETL to suppress interface recombination and enhance device efficiency.
• To demonstrate the scalability and practical application of the developed technology.

Main Methods:

• Investigated the synergistic effects of band misalignment and electron accumulation at the ETL/perovskite interface.
• Developed a continuously graded n+/n-doped SnO2 ETL using a ligand-competitive binding strategy.
• Fabricated n-i-p PSCs utilizing the engineered ETL and evaluated their performance.

Main Results:

• Identified synergistic band misalignment and electron accumulation as the cause of recombination losses.
• The graded SnO2 ETL created a built-in electric field, minimizing band offset and accelerating electron extraction.
• Achieved a certified steady-state power conversion efficiency (PCE) of 27.17% for n-i-p PSCs, the highest reported.
• Demonstrated scalability with a 1 cm2 device PCE of 25.79% and a 16.02 cm2 module PCE of 23.33%.

Conclusions:

• The developed graded ETL strategy effectively suppresses cross-interface recombination in n-i-p PSCs.
• This approach overcomes a fundamental efficiency bottleneck in conventional perovskite photovoltaics.
• Establishes a generalized paradigm for energy-band engineering in metal-oxide transport layers for improved solar cell performance.