Anion Component Engineering of Spontaneous Perovskite Passivators for Energy Alignment Modulations in Perovskite Solar Cells

Why It Matters

Tailoring HTM anions directly tunes energy alignment, boosting efficiency and longevity of perovskite solar cells—a critical step toward commercial viability.

Key Takeaways

• OA-FSI, OA-TFSI, OA-PFSI act as spontaneous passivators
• Anion variation tunes HTM ionization energy
• Deeper IEs improve energy level alignment in PSCs
• FSI additives yield shallower IEs and better stability
• Bis(fluorosulfonyl)imide choice impacts photovoltaic performance

Pulse Analysis

Perovskite solar cells have surged as a high‑efficiency, low‑cost alternative to silicon, yet their hole‑transport materials (HTMs) remain a bottleneck. Conventional spiro‑OMeTAD suffers from limited hole mobility and sub‑optimal energy alignment with the perovskite absorber, prompting researchers to explore molecular additives that can simultaneously passivate surface defects and adjust electronic properties. By incorporating n‑octylammonium cations paired with bis(fluorosulfonyl)imide anions, the study creates a dual‑function additive that integrates seamlessly during HTM deposition, eliminating extra processing steps while delivering spontaneous surface passivation.

The crux of the investigation lies in anion engineering. Moving from FSI to TFSI and PFSI expands the fluorinated moiety, which delocalizes electrons more effectively and deepens the ionization energy of the HTM. This shift fine‑tunes the valence‑band offset between spiro‑OMeTAD and the perovskite layer, facilitating more efficient hole extraction and reducing recombination losses. Notably, the FSI‑based additive produces a shallower ionization energy, striking a balance that enhances both charge transport and device stability—a nuance often overlooked in prior additive studies.

Beyond immediate performance gains, the work signals a broader design paradigm for perovskite photovoltaics. By demonstrating that subtle anion modifications can control energy alignment and durability, it opens pathways for custom‑tailored HTM formulations targeting specific device architectures. Future research may combine this anion strategy with novel cation chemistries or explore its impact on large‑area modules, accelerating the transition of perovskite technology from laboratory prototypes to commercial products.