A Bifunctional Carbazide Additive For Durable CsSnI₃ Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Inorganic CsSnI3 is a promising, low-toxicity photovoltaic material with a narrow bandgap.
• CsSnI3 perovskite solar cells (PSCs) lag behind Pb-based and hybrid Sn-based PSCs due to poor film formation and Sn4+ induced deep traps.

Purpose of the Study:

• To enhance the performance and stability of CsSnI3 PSCs.
• To address the limitations of poor film quality and deep trap defects in CsSnI3.

Main Methods:

• A bifunctional additive, carbazide (CBZ), was employed for film deposition.
• Two-step annealing (80°C and 150°C) was used to improve film quality and reduce defects.
• The coordination of CBZ with Sn2+ and the decomposition of CBZ to reduce Sn4+ were investigated.

Main Results:

• Carbazide facilitated the formation of a pinhole-free CsSnI3 film with large grains.
• The annealing process with CBZ effectively removed deep traps by reducing Sn4+ to Sn2+.
• The CsSnI3:CBZ PSC achieved a record power conversion efficiency of 11.21% (certified 10.90%), a significant improvement over the control device (4.12%).
• Unsealed devices demonstrated good stability under various conditions.

Conclusions:

• Carbazide is an effective additive for improving CsSnI3 film quality and reducing defects in PSCs.
• The developed CsSnI3:CBZ PSCs represent a significant advancement in low-toxicity perovskite solar cell technology.
• The findings pave the way for highly efficient and potentially more stable inorganic perovskite solar cells.