Interfacial Bidirectional Anchoring for CsPbI3 Phase Stabilization in Inverted Perovskite Solar Cells

Why It Matters

Stabilizing black CsPbI3 bridges the gap between high efficiency and long‑term reliability, a critical hurdle for commercial perovskite photovoltaics.

Key Takeaways

• SMCl anchors both Cs+ and PbI6 octahedra
• Dual-site interaction induces compressive strain
• Stabilized black CsPbI3 yields 21.17% efficiency
• Device retains 85% efficiency after 1000 h at 65 °C
• Inverted architecture compatible with scalable manufacturing

Pulse Analysis

Perovskite solar cells have surged ahead of traditional silicon due to their rapid efficiency gains, yet their commercial adoption remains hampered by phase instability. Inorganic cesium lead iodide (CsPbI₃) offers superior thermal resilience compared with mixed‑cation formulations, but its photoactive black phase is metastable and readily converts to a non‑absorbing yellow phase under heat or moisture. This intrinsic volatility stems from the small ionic radius of Cs⁺, which can migrate within the [PbI₆]⁴⁻ framework, prompting octahedral tilting and structural collapse. Overcoming this challenge is essential for delivering durable, high‑performance modules.

The bidirectional anchoring approach leverages SMCl’s bifunctional chemistry to lock both cationic and anionic sublattices in place. The sulfonate moiety forms strong electrostatic interactions with Cs⁺, curbing its displacement, while the imidazolium ring coordinates to the lead‑iodide octahedra, limiting tilting. Simultaneously, these dual bonds generate a compressive strain across the film, further reinforcing the black phase. Compared with conventional surface passivation or additive strategies, this method provides a synergistic, lattice‑level stabilization without sacrificing carrier mobility, enabling an unprecedented 21.17% efficiency in an inverted device architecture.

Beyond the laboratory, the technique aligns with scalable manufacturing pathways. Inverted perovskite stacks are compatible with low‑temperature processing and flexible substrates, and the SMCl treatment can be integrated as a simple post‑deposition rinse, avoiding complex deposition steps. The demonstrated thermal endurance—85% efficiency retention after 1,000 hours at 65 °C—addresses a primary reliability concern for utility‑scale deployment. As the industry pushes toward >25% efficiencies, strategies that simultaneously lock crystal structure and maintain high optoelectronic quality will be pivotal, positioning bidirectional anchoring as a promising cornerstone for the next generation of commercial perovskite photovoltaics.