Multivalent ligands regulate dimensional engineering for inverted perovskite solar modules

Area of Science:

• Materials Science
• Chemical Engineering
• Solid-State Chemistry

Background:

• Conventional monovalent ammonium ligands in low-dimensional perovskites exhibit limitations in chemical coordination and deprotonation.
• Multivalent, resonance-stabilized amidinium ligands offer improved properties for perovskite applications.

Purpose of the Study:

• To introduce a strategy for controlling the structural transition from one-dimensional (1D) to two-dimensional (2D) amidinium perovskites.
• To elucidate the relationship between molecular structure, interfacial interactions, and resulting dimensionality.
• To optimize interfacial properties for enhanced solar cell performance.

Main Methods:

• Systematic tuning of ligand conformation to modulate hydrogen bonding, π-π stacking, and basicity.
• Investigating the impact of 1D and 2D amidinium perovskite structures on surface coverage and defect passivation.
• Fabricating and characterizing inverted 3D/2D-amidinium perovskite solar cells.

Main Results:

• The 1D-amidinium perovskite structure shows geometric anisotropy, hindering uniform surface coverage and defect passivation.
• The 2D-amidinium perovskite forms a continuous, homogeneous interfacial layer, leading to effective defect passivation and favorable energy-level alignment.
• Optimized 3D/2D-amidinium perovskite solar cells achieved 25.4% power conversion efficiency and maintained over 95% initial efficiency after 1100 hours of operation at 85°C.

Conclusions:

• Controllable 1D-to-2D structural transition of amidinium ligands is crucial for optimizing perovskite solar cell performance.
• The 2D-amidinium perovskite structure provides superior interfacial properties for defect passivation and energy alignment.
• This strategy enables highly efficient and stable perovskite solar cells.