Sequential Passivation for Lead-Free Tin Perovskite Solar Cells with High Efficiency

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Lead-free tin perovskite solar cells (PKSCs) are a promising alternative to lead-based devices.
• Low efficiency and poor stability in tin PKSCs stem from surface roughness, defects, rapid crystallization, and oxidation.
• Existing research seeks effective passivation strategies to overcome these limitations.

Purpose of the Study:

• To develop a facile and universal post-treatment strategy for enhancing tin PKSC efficiency and stability.
• To address issues of surface morphology and defect density in lead-free PKSCs.
• To investigate the impact of sequential passivation using acetylacetone (ACAC) and ethylenediamine (EDA).

Main Methods:

• A sequential passivation technique using acetylacetone (ACAC) followed by ethylenediamine (EDA) was applied as a post-treatment.
• The effects of ACAC and EDA on trap density, grain size, tin coordination, and energy levels were analyzed.
• Alternative combinations of diketones and amines were explored to assess the universality of the strategy.

Main Results:

• Acetylacetone (ACAC) reduced trap density and increased grain size, boosting short-circuit current (Jsc).
• Ethylenediamine (EDA) passivated undercoordinated tin and regulated energy levels, enhancing open-circuit voltage (Voc).
• A peak efficiency of 13% was achieved with improved operational stability.

Conclusions:

• The sequential ACAC/EDA post-treatment is a universal and effective strategy for fabricating high-efficiency, stable lead-free tin PKSCs.
• This method successfully enhances crystallinity and passivates defects, overcoming key challenges in tin-based perovskite technology.
• The findings pave the way for the commercial viability of lead-free perovskite solar cells.