Researchers from the Korea Institute of Energy Technology (KENTECH), Korea Research Institute of Chemical Technology (KRICT) and Ulsan National Institute of Science and Technology (UNIST) have developed a molecularly engineered interfacial passivation strategy that significantly improves the stability, scalability and processing tolerance of perovskite solar cells.
Halide perovskite solar cells remain constrained by poor durability and narrow processing windows. Conventional ammonium halide-based passivation approaches form 2D/3D heterostructures that effectively reduce defects and improve charge selectivity, but their metastable nature and strong sensitivity to fabrication conditions lead to performance variability, especially in large-area manufacturing. To address these challenges, the team designed an amorphous π-conjugated passivator, (4-(3-iodo-9H-carbazol-9-yl)butyl)phosphonic acid (I-4PACz), specifically targeting improved interfacial control between the perovskite absorber and the hole transport layer (HTL). The molecular design incorporates a carbazole core with an asymmetric iodine substituent at the 3-position, which plays a dual role in modulating both electronic and structural properties.
The presence of the iodine atom increases the molecular dipole moment due to its high electronegativity, enabling more favorable energy-level alignment at the perovskite/HTL interface and facilitating efficient charge extraction. At the same time, the asymmetric substitution alters intermolecular interactions by redistributing electron density, suppressing ordered molecular packing and promoting the formation of an amorphous, uniformly distributed interfacial layer.
This amorphous character is critical: unlike crystalline passivation layers that are highly sensitive to thickness and deposition conditions, I-4PACz maintains consistent performance across a wide range of processing parameters. Devices incorporating the material showed minimal efficiency variation even when the passivator concentration changed by approximately an order of magnitude, demonstrating thickness-independent behavior and a significantly widened process window.
In practical device configurations, the improved interfacial energetics and morphology translate into enhanced junction quality and more efficient charge carrier transfer. As a result, perovskite solar modules fabricated with I-4PACz achieved a power conversion efficiency of 21.2% over a 24.5 cm² aperture area, approaching the typical 21–22% efficiency range of commercial silicon modules.
Equally important, the devices demonstrated strong operational stability. The modules retained 85% of their initial efficiency after 884 hours under conditions of 65°C and 40% relative humidity, and 98.7% after 525 hours of continuous illumination. These results highlight the improved robustness of the amorphous interface under both thermal and light stress.
From a manufacturing perspective, the material shows low sensitivity to blade-coating speed, a key parameter in scalable thin-film deposition. This robustness enables consistent device performance even under varying coating conditions, addressing a major bottleneck in transitioning perovskite technologies to roll-to-roll and inline production systems.
the researchers said: “We have simultaneously secured the process stability and reproducibility required in real industrial manufacturing,” and added, “Because this material can be readily applied to existing R2R continuous and large-area production processes, it is expected to accelerate the commercialization of perovskite solar cells.”
Overall, the study demonstrates that molecular design strategies combining high dipole moments with amorphous structural characteristics can simultaneously deliver efficiency, stability, and manufacturability - key requirements for the large-scale deployment of perovskite photovoltaics.
