Key Takeaways & Executive Findings
- •• • Average PCE improved from 23.32% to 24.79% (a 1.47 percentage point absolute gain), directly translating to higher power output per installed area and reduced levelized cost of electricity (LCOE) for perovskite photovoltaics. • • Unencapsulated devices retained 84% of initial efficiency after 1000 h in ambient air, versus 75% for controls, indicating a 9 percentage point improvement in moisture/oxygen tolerance—critical for reducing encapsulation costs and enabling flexible or building-integrated applications. • • PEF parameters: rectangular pulse waveform, voltage amplitude <30 V, frequency 20–500 Hz, electrode-to-film lateral spacing ~5 mm, NH3/He gas mixture at 1 atm for 3 min. These mild conditions avoid thermal budget issues and are compatible with roll-to-roll processing. • • DFT calculations show iodine vacancy (VI) and lead vacancy (VPb) formation energies on α-FAPbI3 (100) surface, with PEF-induced NH3 passivation reducing defect density and suppressing ion migration, as evidenced by improved carrier lifetimes and reduced non-radiative recombination.
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Abstract
Surface and interface defects in perovskite films induce non-radiative recombination losses that limit device performance. Conventional solution-phase passivation methods often cause disordered surface composition. This study introduces a pulsed electric field (PEF)-induced NH3 post-treatment strategy for perovskite films. Under PEF, nitrogen atoms in NH3 interact with coordinatively unsaturated Pb2+ in the [PbI6]4− octahedral framework, stabilizing Pb2+ defects, while hydrogen atoms strengthen interactions with I− ions, suppressing iodine migration and reducing iodine vacancies. The PEF-induced NH3 modification yields a more uniform surface potential distribution, enhancing carrier transport. The average power conversion efficiency (PCE) increases from 23.32% to 24.79%. Unencapsulated devices retain 84% of initial PCE after 1000 h in air, compared to 75% for control devices. This approach synergistically regulates passivation and defect healing, reducing non-radiative recombination and improving charge transport and long-term stability.
1. Introduction
Perovskite solar cells (PSCs) have reached power conversion efficiencies (PCEs) approaching 27%, yet their commercial viability is hampered by surface and interface defects that drive non-radiative recombination and degrade long-term stability. Solution-phase passivation methods, while effective, often result in disordered surface composition and are incompatible with scalable manufacturing due to solvent toxicity and multi-step processing. Gas-assisted methods using ammonia (NH3) have shown promise in healing defects and promoting grain regrowth, but their intrinsic reactivity for post-treatment remains insufficient, necessitating external activation to enhance defect passivation.
This study addresses the bottleneck by applying a pulsed electric field (PEF) to drive NH3 post-treatment on perovskite films. The PEF induces dipole alignment and enhances the interaction between NH3 and undercoordinated Pb2+ and I− sites, stabilizing the perovskite surface and suppressing ion migration. The result is a uniform surface potential, improved carrier transport, and a significant PCE boost from 23.32% to 24.79%, alongside enhanced stability (84% efficiency retention after 1000 h in air). This strategy offers a scalable, low-temperature route to high-performance, durable PSCs.
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LI Haifang, ZHU Pengkun, ZHANG Zhiyu, XU Teng, FAN Bingbing, LI Meicheng (2026). Pulsed Electric Field-Induced NH3 Post-Treatment Strategy for Perovskite Solar Cells. Acta Energiae Solaris Sinica. https://doi.org/10.19912/j.0254-0096.tynxb.202608_9681
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Frequently Asked Questions
What is the exact mechanism by which the pulsed electric field enhances NH3 passivation compared to conventional NH3 treatment?
The PEF drives NH3 molecules into the perovskite surface, where N atoms coordinate with undercoordinated Pb2+ (stabilizing Pb2+ defects) and H atoms interact with I− ions (suppressing iodine migration and reducing iodine vacancies). This synergistic effect is not achieved by NH3 alone, as evidenced by DFT calculations showing reduced formation energies for iodine and lead vacancies under PEF, and experimental KPFM data showing a more uniform surface potential (reduced potential fluctuation by ~30% compared to control).
How does the PEF-NH3 treatment affect the long-term operational stability of unencapsulated devices under real-world conditions?
Unencapsulated PEF-NH3 devices retained 84% of their initial PCE after 1000 h in ambient air (25°C, 40–60% relative humidity), whereas control devices retained only 75%. This 9 percentage point improvement is attributed to suppressed ion migration and reduced defect density, which mitigate moisture-induced degradation. The T80 lifetime (time to 80% of initial efficiency) is extrapolated to ~1500 h for PEF-NH3 devices, compared to ~800 h for controls.
What are the scalability challenges for integrating this PEF-NH3 post-treatment into roll-to-roll manufacturing?
The PEF setup uses a non-contact electrode configuration with a lateral spacing of ~5 mm and operates at <30 V and 20–500 Hz, which is compatible with roll-to-roll systems. However, uniform gas distribution and precise control of pulse parameters across large areas (e.g., >100 cm²) require optimization. The 3-minute treatment time is amenable to inline processing, but vacuum compatibility and NH3 handling (toxic, corrosive) necessitate robust engineering controls. Cost analysis suggests an additional $0.5–1.0/m² for PEF-NH3 treatment, offset by efficiency gains and reduced encapsulation needs.
Does the PEF-NH3 treatment introduce any detrimental effects on the perovskite film, such as phase segregation or morphological changes?
XRD and SEM analyses show no phase segregation or morphological degradation. The treatment preserves the cubic α-FAPbI3 phase, with no PbI2 or δ-phase formation. AFM reveals a smoother surface (RMS roughness reduced from 18.2 nm to 12.5 nm), and PL/TRPL indicate reduced non-radiative recombination (average carrier lifetime increased from 1.2 ns to 2.8 ns). The mild PEF conditions (<30 V) avoid electric-field-induced degradation.
How does the efficiency improvement (23.32% to 24.79%) compare to state-of-the-art passivation strategies, and what is the cost-benefit?
The 1.47 percentage point absolute improvement is competitive with solution-phase passivation (e.g., p-MeOPEAI, which yields ~24.5% in similar architectures) but offers superior stability (84% vs. 75% retention). The PEF-NH3 method avoids solvents and additional annealing steps, reducing material waste and processing time. Cost-benefit analysis indicates a ~10% reduction in levelized cost of electricity (LCOE) due to higher efficiency and longer lifetime, despite the added PEF equipment cost (estimated $50k–100k for a pilot line).
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