Efficient Perovskite Solar Cells Based on Tin Oxide Nanocrystals with Difunctional Modification

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Tin oxide (SnO₂) nanocrystals are crucial for perovskite solar cells (PSCs) as electron transport layers (ETLs) due to their charge mobility and band alignment.
• However, high surface trap density in SnO₂ hinders electron transfer and collection, limiting device efficiency.

Purpose of the Study:

• To develop an effective method for creating low trap density and high electron mobility SnO₂ ETLs for PSCs.
• To improve electron transfer and collection efficiency in PSCs by passivating traps and optimizing energy level alignment.

Main Methods:

• Incorporation of a difunctional additive, potassium trifluoroacetate (KTFA), into the SnO₂ nanocrystal solution.
• Trifluoroacetate ions (TFA^-) were used to passivate oxygen vacancies (O_V) in SnO₂ by binding with Sn⁴⁺, reducing trap density.
• Surface modification of SnO₂ nanocrystals to shift their conduction band edge closer to that of perovskite.

Main Results:

• Passivation of oxygen vacancies in SnO₂ by KTFA effectively reduced surface trap density.
• Surface modification shifted the conduction band of SnO₂, decreasing the energy barrier for electron transfer from perovskite.
• The modified SnO₂ ETL enabled perovskite solar cells to achieve a power conversion efficiency of 21.73% with negligible hysteresis.

Conclusions:

• Potassium trifluoroacetate is an effective additive for fabricating high-performance SnO₂ ETLs for perovskite solar cells.
• Reducing trap density and optimizing energy level alignment are critical for enhancing electron transport and collection in PSCs.
• The developed method offers a promising strategy for advancing perovskite solar cell technology.