Robust and Tailored 1D/3D Heterojunction for Efficient and Stable Perovskite Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• Operational stability is a key challenge for organic-inorganic hybrid perovskite solar cells (PSCs).
• Low-dimensional perovskites offer a promising approach to improve device robustness.
• The role of spacer cations in regulating 1D/3D heterojunctions for stability is not well understood.

Purpose of the Study:

• To investigate the impact of spacer cations on 1D/3D heterojunction stability in PSCs.
• To synthesize and characterize new 1D perovskite single crystals using benzamidinium (BZ) and trifluoromethyl benzamidinium (TFBZ) spacer cations.
• To establish a design strategy for enhancing the efficiency and stability of perovskite photovoltaics.

Main Methods:

• Synthesis of two new 1D perovskite single crystals: (BZ)2Pb1.5I4 and (TFBZ)PbI3.
• Structural and chemical analysis to understand the role of spacer cations.
• Fabrication and performance testing of 1D/3D hybrid PSCs incorporating the synthesized 1D perovskites.

Main Results:

• TFBZ spacer cations, with trifluoromethyl groups, form extensive hydrogen-bond networks and exhibit a high dipole moment.
• These features enhance the interaction between TFBZ and the inorganic [PbI6]4- skeleton, leading to stable, orientationally crystallized 1D perovskites.
• The incorporation of 1D (TFBZ)PbI3 resulted in a robust 1D/3D heterojunction with favorable lattice matching, strong interface binding, and effective defect passivation.
• TFBZ-based 1D/3D hybrid PSCs achieved a power conversion efficiency of 25.54% with exceptional operational and thermal stability.

Conclusions:

• Spacer cation engineering, specifically using TFBZ, is crucial for controlling the microstructure of 1D/3D heterojunctions.
• The developed 1D/3D heterojunction strategy significantly enhances the stability and efficiency of perovskite solar cells.
• This work provides a valuable design principle for developing highly efficient and stable perovskite photovoltaics.