Publication date: 5th November 2025
Interfacial instability at the perovskite/electron-transport-layer (ETL) interface remains a key barrier to achieving durable high-performance inverted perovskite solar cells (PSCs). Phenethylammonium iodide (PEAI) is an effective passivator but its excessive reactivity often induces uncontrolled formation of 2D/quasi-2D phases such as (PEA)₂PbI₄, triggering interfacial degradation and hindering charge extraction[1]. Here, we report a sequential synergistic passivation strategy using a multifunctional penta-carboxyphenyl-functionalized fullerene (PCPF) as a molecular buffer prior to PEAI deposition[2]. The abundant –COOH groups in PCPF mildly coordinate with under-coordinated Pb²⁺ to repair surface defects, while its electron-rich fullerene framework establishes a favorable interfacial dipolar environment. This molecular buffer effectively suppresses PEA⁺ deprotonation and prevents the overgrowth of thick 2D perovskite layers during subsequent PEAI treatment. Instead, a thin and well-controlled quasi-2D structure is formed, providing secondary defect passivation without introducing an electron-blocking barrier.
The engineered PCPF/PEAI heterointerface yields substantial improvements in device performance, including enhanced electronic passivation, optimized energy-level alignment, prolonged carrier lifetime, and reduced interfacial recombination. As a result, the optimized inverted PSC achieves a PCE of 25.5%—significantly higher than the 20.8% of the control device—and maintains over 91% of its initial efficiency after 1000 h of continuous operation.
This work demonstrates that interfacial sequence engineering offers an effective pathway to regulate the reaction dynamics of organic ammonium salts. The synergistic fullerene–PEAI strategy provides a generalizable design principle for constructing stable, low-defect, and energetically favorable interfaces, paving the way toward highly efficient and durable inverted perovskite optoelectronic devices.
This research was supported by the CREST program of the JST, Grant Number JPMJCR25A4
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