Solution-Processed Ge-Sn (1:1) Perovskite Solar Cells with a DMSO-Free Solvent System and GeCl2-Dioxane Additives

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• Lead (Pb) toxicity necessitates lead-free alternatives for halide perovskite solar cells.
• Tin (Sn) and Germanium (Ge) are promising eco-friendly substitutes due to similar electronic properties and reduced toxicity.

Purpose of the Study:

• To address the reactivity of GeI2 in dimethyl sulfoxide (DMSO) solvents.
• To develop a novel solvent system for stable Ge-Sn perovskite film formation.
• To enhance the performance and stability of Ge-Sn perovskite solar cells.

Main Methods:

• Investigated the reactivity of DMSO with GeI2.
• Introduced a new solvent system: N,N-dimethylformamide:N-N'-dimethylpropyleneurea:4-tert-butylpyridine.
• Employed a GeCl2-dioxane complex (1:1) alloying strategy to control crystallization and improve Ge integration.
• Fabricated Ge-Sn (1:1) perovskite solar cells using a wet-coating method.

Main Results:

• A DMSO-free solvent system was successfully developed, preventing unwanted reactions.
• Pure-phase Ge-Sn (1:1) perovskite films with improved crystallinity and optoelectronic properties were formed.
• The Ge-Sn (1:1)-alloyed solar cells achieved a record 4.56% power conversion efficiency using a solution method.
• The devices demonstrated high operational stability, retaining 91% of initial efficiency after 50 hours of continuous illumination.

Conclusions:

• The novel solvent system and alloying strategy are effective for fabricating high-performance Ge-Sn perovskite solar cells.
• This research offers a viable pathway towards stable and efficient lead-free perovskite photovoltaics.
• The achieved efficiency represents a significant advancement in solution-processed perovskite solar cell technology.