What the patent landscape tells us about perovskite white spot degradation

More than 50 active, pending, or recently granted patents spanning jurisdictions including South Korea, Japan, the United States, China, Brazil, Italy, and the European Union form the evidentiary foundation for understanding white spot degradation in perovskite solar panels. The most frequently appearing assignees include Hanwha Solutions Corporation, Korea Electric Power Corporation (KEPCO), Oxford University Innovation Limited, ENI S.P.A., the University of North Carolina at Chapel Hill, Huawei Technologies, and Kyushu University — a mix of industrial manufacturers and academic institutions that signals both commercial urgency and fundamental scientific challenge.

Dominant technical approaches cluster around four themes: ionic defect passivation within the perovskite photoactive layer; interface engineering between the perovskite and charge-transport layers; UV filtering and encapsulation strategies; and post-treatment processes to reverse thermal degradation incurred during module manufacturing. Together, these reflect a broad consensus that white spot and related efficiency losses originate from multiple interacting mechanisms, each requiring targeted solutions.

Ionic defects and thermal stress: the manufacturing problem that cannot be avoided

The most direct cause of localized efficiency loss in perovskite solar panels — including the white and dark spots visible under electroluminescence imaging — is the accumulation of cationic and anionic defects generated during the lamination and module assembly process. High temperatures and pressures applied during manufacturing drive ion migration and defect formation that cannot be easily reversed without post-treatment, as documented in patents from Hanwha Solutions Corporation (2026).

Within the perovskite crystal lattice itself, shallow-level defects form readily during spin-coating and annealing. These include uncoordinated Pb²⁺ ions, Pb-I antisite defects, metallic lead clusters, and iodine vacancies — all of which create charge recombination centers that impede carrier extraction and transport, as stated in a 2025 patent from Beijing University of Technology. Additional defect types in electron transport layers, such as oxygen vacancies (VO) and tin vacancies (VSn) in SnO₂, compound the problem by creating interfacial recombination pathways.

Ion migration under illumination or applied voltage is a critical secondary mechanism. Oxygen vacancies in the SnO₂ electron transport layer (ETL) prevent iodine fixation within the perovskite structure. The resulting iodine interstitial defects (Ii) cause phase transitions to δ-FAPbI₃ or PbI₂ — both semiconductorically unsuitable phases that manifest as non-photoactive, effectively “white” regions in the active layer, as explained in a 2024 Yonsei University patent. Ion migration also enables direct contact between perovskite species and metal electrodes, accelerating irreversible decomposition.

“Oxygen vacancies in SnO₂ at the ETL/perovskite interface prevent iodine fixation within the perovskite structure; the resulting iodine interstitial defects cause phase transitions to δ-FAPbI₃ or PbI₂ — non-photoactive phases that manifest as white regions in the active layer.”

Intragrain impurities — specifically secondary-phase precipitates such as (M²⁺)(X⁻)₂ and (A⁺)(X⁻) inclusions within individual perovskite crystal grains — represent an underappreciated structural source of degradation. These inclusions act as local recombination centers and nucleation sites for further decomposition. Research from The Hong Kong University of Science and Technology (HKUST, 2025) explicitly addresses this, demonstrating that laser or electron beam irradiation can selectively reduce such intragrain impurities, as documented in HKUST‘s patent filings.

UV exposure, moisture ingress, and the phase transitions that create visible white spots

Extrinsic environmental stressors — UV radiation, moisture, oxygen, and elevated temperature — are well-established accelerants of perovskite decomposition that directly cause the visible white and yellow discoloration associated with white spot degradation. A 2020 patent from Kyushu University identifies these four factors as the primary extrinsic limiters of perovskite stability, noting that they trigger carrier trap formation and phase transitions that degrade both efficiency and device lifetime.

UV light drives iodide oxidation within the perovskite lattice, generating molecular I₂. This I₂ then decomposes the organic cation components of hybrid perovskites, leaving behind PbI₂-rich regions — the white or yellow discolored spots observable in degraded panels. The quantitative impact is stark: devices without UV filters degraded to only 14% of their initial efficiency under prolonged UV exposure, while carbon quantum dot (CQD)-filtered devices retained 90% of their initial performance after more than 900 hours, as demonstrated by IIT Kanpur (2023). According to NREL and broader photovoltaic research community standards, such accelerated degradation under UV is a critical barrier to perovskite commercialization.

Moisture infiltration accelerates the hydrolysis of methylammonium lead iodide (MAPbI₃) to PbI₂, MAI, and ultimately Pb(OH)₂ — all of which are optically distinct from the functional perovskite phase and contribute to visible discoloration and white spot formation. Pinhole suppression through controlled antisolvent application combined with ventilation is specifically targeted in a 2025 Toyota Motor Corporation patent, which recognizes that pinholes in the photoelectric conversion layer are a primary pathway for moisture penetration and localized degradation. This aligns with encapsulation standards published by bodies such as IEC for photovoltaic module durability testing.

Passivation and interface engineering: the primary prevention strategies in the patent record

Chemical passivation of ionic defects within the perovskite layer, at grain boundaries, and at interfaces with charge-transport layers is the dominant prevention strategy across the patent landscape. Passivating agents operate by chemically bonding to exposed cations or anions in the perovskite lattice, eliminating dangling bonds that would otherwise act as recombination centers — a broad principle covered in a foundational 2020 patent from Oxford University Innovation Limited.

Bifunctional and zwitterionic passivating agents

Zwitterionic and bifunctional molecules that can simultaneously passivate both positive and negative charge defects have emerged as particularly effective. A 2026 patent from Henan Ancai Glass Research Institute demonstrates that zwitterionic inner salt compounds with N⁺ groups (which passivate negatively charged defects such as migrating Br⁻ and Br vacancy sites) and SO₃⁻ groups (which passivate positively charged defects such as BiCs antisite defects) can simultaneously suppress ion migration and improve both efficiency and long-term stability in lead-free double perovskites. Bifunctional polymers with side chains containing groups that passivate both positively and negatively charged grain boundary defects have also been demonstrated to significantly reduce deep-level defect concentrations, as reported in a 2021 patent from the Qingdao Institute of Bioenergy and Bioprocess Technology.

Specific molecular classes reported in the patent data include: phenyl sulfone small molecules (Zhejiang University of Technology, 2024); aza-fused bicyclic organic compounds (Contemporary Amperex Technology, 2024); polyacrylic acid incorporated directly into the perovskite precursor (ENI S.P.A., 2025); and the organic molecule 2-PO incorporating =N-OH functional groups that prevent I₂ generation under photo-thermal aging (Henan Academy of Sciences, 2026). Passivation using parylene-based conformal deposited layers has also been patented by Chungnam National University (2026).

Interface engineering at the ETL and HTL junctions

Because white spots and efficiency losses often initiate at layer interfaces, substantial IP activity targets the perovskite/ETL and perovskite/HTL junctions. Oxygen vacancy passivation in the SnO₂ ETL is addressed in a 2024 Yonsei University patent, which uses oxidized black phosphorus quantum dots (O-BPs) rich in P=O bonds to passivate SnO₂ₓ oxygen vacancies, thereby preventing iodine interstitial formation and blocking the δ-FAPbI₃ and PbI₂ phase transitions that produce non-photoactive white regions.

Surface defect removal from the perovskite layer itself — a physical rather than chemical strategy — is patented by the University of North Carolina at Chapel Hill (2024), which discloses mechanical removal of surface defect layers by adhesive tape or polishing, yielding polycrystalline films free of defect-rich surface regions with enhanced efficiency and stability. Ion diffusion barriers placed between the light-absorbing layer and charge-transport layers directly prevent the ionic migration that causes progressive phase segregation, as covered in a 2019 Korea University patent. Surface conversion of perovskite surfaces to insoluble wide-bandgap lead oxysalts represents another interfacial stabilization strategy, as disclosed by NUtech Ventures (2022).

Film quality and crystallization control

Higher-quality perovskite films with large grain sizes and low intrinsic defect densities are inherently more resistant to white-spot formation. Manufacturing approaches targeting film morphology include antisolvent-assisted crystallization (KEPCO, 2025) and supersaturation-suppressed crystal growth yielding grains above 1 µm (KEPCO, 2026). Metal doping to reduce vacancy density and superoxide formation is addressed in the University of Toronto’s 2021 disclosure on doped metal halide perovskites, with research published in journals indexed by Nature supporting the broader principle that vacancy reduction extends perovskite operational lifetime under ambient conditions.

Post-treatment and in-field remediation: reversing degradation that has already occurred

A growing body of IP addresses reversal or mitigation of degradation that has already occurred — either during manufacturing or in field operation — signalling increased recognition that some degree of degradation is unavoidable and must be corrected rather than solely prevented.

Hanwha Solutions Corporation has filed extensively across multiple jurisdictions on post-treatment methods specifically targeting thermally induced cell degradation during module manufacturing. Korean (2025) and Japanese (2026) filings describe post-treatment protocols applied after module lamination to reverse ionic defect accumulation and restore photovoltaic parameters including Voc, Jsc, FF, and overall power output. This is complemented by Hanwha’s interface treatment patents (2024 and 2025), which address simultaneous surface defect removal and energy-level matching with the ETL.

For in-field photovoltaic modules experiencing potential-induced degradation (PID) — a closely related phenomenon involving surface polarization and efficiency loss under operating electrical bias — Huawei Technologies has developed a signal-based remediation approach. US and European patents filed in 2020 describe applying a high-frequency signal to an affected module to suppress or eliminate PID, restoring electrical energy conversion capability without physical disassembly. This approach is relevant to perovskite modules as the technology matures toward grid-scale deployment, a transition tracked by organizations including IEA in their annual solar photovoltaic market reports.

Beam-based intragrain impurity reduction — using laser or electron beam irradiation to selectively eliminate secondary-phase inclusions within perovskite grains — represents a potentially high-precision post-treatment method, as disclosed by HKUST (2025). Quantum dot surface stabilization post-treatment specifically addressing defects arising from the ligand exchange step has been developed by DGIST (2025). These approaches complement fabrication-stage strategies and point toward a future where perovskite module maintenance may include active defect remediation.

Key players, assignee strategies, and the trend toward multi-mechanism solutions

The patent data reveals a competitive landscape concentrated among a handful of repeat filers, each pursuing distinct technical strategies that together cover the full manufacturing and operational lifecycle of perovskite modules.

Hanwha Solutions Corporation is the most prolific perovskite-specific assignee in the dataset, with multiple filings in Korea, Japan, and China covering post-treatment against thermal degradation, interface treatment for surface defect removal, passivation layer introduction between ETL and electrodes, and hole transport layer oxidation processes. Their filings reflect a systematic effort to cover the entire perovskite module manufacturing process from cell to encapsulated module.

Korea Electric Power Corporation (KEPCO) focuses on manufacturing process innovation — antisolvent processing, supersaturation suppression for large grain growth above 1 µm, and semitransparent tandem structures — with multiple active Korean patents demonstrating a drive toward commercializable, high-stability devices.

Oxford University Innovation Limited holds broad foundational patents on passivating agent chemistry and mixed-anion perovskite compositions that underpin many subsequent stability improvements across the industry.

ENI S.P.A. (with Consiglio Nazionale delle Ricerche) has built a portfolio around polyacrylic acid and polysaccharide polymer incorporation into perovskite precursor solutions for both opaque and semitransparent cells, active in Brazil and Italy. Huawei Technologies owns signal-based in-field PID remediation technology applicable across silicon and emerging perovskite module types, active in the US, EP, and AU jurisdictions.

Academic institutions — Yonsei University, HKUST, University of North Carolina at Chapel Hill, IIT Kanpur, and Kyushu University — are active in advanced passivation chemistry, beam-based defect remediation, surface treatment, UV filtering, and thermally stable film development. Their foundational disclosures frequently precede and inform subsequent industrial filings.

“Single-component solutions are giving way to dual-function or hierarchical approaches that simultaneously address defect passivation, ion migration suppression, moisture barrier function, and energy-level alignment — a convergence toward multi-mechanism strategies across the entire patent landscape.”

A clear trend is the convergence toward multi-mechanism strategies. The growing number of post-treatment and in-field remediation patents signals increased recognition that some degree of degradation during manufacturing and field operation is unavoidable, requiring corrective rather than solely preventive approaches — a perspective increasingly reflected in WIPO‘s annual technology trend reports on photovoltaic innovation.