What actually causes white spots: the four interacting mechanisms

White spot degradation in perovskite solar panels is caused by at least four interacting mechanisms: ionic defect accumulation under thermal and mechanical stress, oxygen vacancy-driven phase transitions, UV-induced iodide oxidation, and moisture-driven hydrolysis. The patent and literature data surveyed for this analysis encompasses 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 — and a broad consensus has emerged that no single mechanism is solely responsible.

The most direct cause of localised efficiency loss — including the appearance of white or dark spots visible under electroluminescence (EL) imaging — is the accumulation of cationic and anionic defects in the perovskite photoactive layer. As documented by Hanwha Solutions Corporation (2026), the module manufacturing process inevitably subjects the perovskite light-absorbing layer to high temperature and/or high pressure, generating defect accumulation that directly reduces power output, open-circuit voltage (Voc), short-circuit current (Jsc), and fill factor (FF).

Within the perovskite crystal lattice itself, shallow-level defects including uncoordinated Pb²⁺ ions, Pb-I antisite defects, metallic lead clusters, and iodine vacancies act as charge recombination centers. As stated by Beijing University of Technology (2025), these defects form readily during spin-coating and annealing of the perovskite film, creating recombination centers that impede carrier extraction and transport. Oxygen vacancies (VO) and tin vacancies (VSn) in the SnO₂ electron transport layer further compound the problem by creating interfacial recombination pathways.

Ion migration — particularly the drift of iodine interstitials (Ii) under illumination or applied voltage — is a critical secondary mechanism. Research from Yonsei University (2024) explains that oxygen vacancies in the SnO₂ electron transport layer prevent iodine fixation within the perovskite structure; the resulting iodine interstitial defects cause phase transitions to δ-FAPbI₃ or PbI₂ — both semiconductorically unsuitable phases that manifest as non-photoactive, effectively “white”, regions in the active layer. Ion migration also enables direct contact between perovskite species and metal electrodes, accelerating irreversible decomposition, as noted by Central South University (2023).

Phase instability, UV radiation, and moisture — the extrinsic accelerants

Extrinsic environmental stressors — primarily UV radiation, moisture, oxygen, and elevated temperature — are well-established accelerants of perovskite decomposition that convert functional perovskite material into visibly distinct, non-photoactive phases. Research from Kyushu University (2020) identifies moisture, oxygen, UV light, and temperature as the primary extrinsic factors limiting perovskite stability, noting that these factors trigger carrier trap formation and phase transitions that degrade both efficiency and device lifetime.

Oxygen exposure under illumination is particularly damaging through a specific mechanism: vacancy sites in the perovskite lattice absorb oxygen molecules and convert them to reactive superoxide species, which then decompose the perovskite framework itself. As described in research from the University of Toronto (2021), perovskites have a high density of vacancies that, upon illumination, absorb oxygen and convert it to superoxide species, which then react with the perovskite to decompose it. Metal doping to reduce vacancy density is one direct response to this pathway.

“Devices without UV filters degraded to only 14% of their initial efficiency under prolonged UV exposure, while carbon quantum dot-filtered devices retained 90% of initial performance after more than 900 hours.”

UV light drives iodide oxidation, generating molecular I₂ which further 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 evidence from the Indian Institute of Technology Kanpur (2023) is striking: unprotected devices degraded to just 14% of initial efficiency under prolonged UV exposure, whereas devices incorporating carbon quantum dot (CQD) UV filters retained 90% of their initial performance after more than 900 hours. CQD filters derived from polyaniline waste provide an elegant dual function: absorbing harmful UV and re-emitting it as visible blue light in the 425–500 nm range that the perovskite can still convert to photocurrent.

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. 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 (2025) demonstrates that laser or electron beam irradiation can selectively reduce such intragrain impurities, offering a high-precision remediation path. As documented by WIPO, the perovskite stability challenge is one of the most active areas of global photovoltaic patent filing activity.

Defect passivation: the dominant prevention strategy across 50+ patents

Chemical passivation of ionic defects within the perovskite layer, at grain boundaries, and at interfaces with charge-transport layers is the single most prevalent prevention strategy across the patent landscape surveyed. 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. Oxford University Innovation Limited’s foundational 2020 patent covers this broad principle: organic passivating agent molecules are chemically bonded to anions or cations in the metal halide perovskite.

Zwitterionic and bifunctional molecules that can simultaneously passivate both positive and negative charge defects have emerged as particularly effective. Research from Henan Ancai Glass Research Institute (2026) 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 antisite defects — can simultaneously suppress ion migration and improve both efficiency and long-term stability in lead-free double perovskites. This dual-function approach represents the current state-of-the-art in chemical prevention.

The range of specific molecular classes reported in the patent data is broad. Phenyl sulfone small molecules have been patented by Zhejiang University of Technology (2024); aza-fused bicyclic organic compounds by Contemporary Amperex Technology (2024); polyacrylic acid incorporated directly into the perovskite precursor by ENI S.P.A. (2025); and the organic molecule 2-PO incorporating =N-OH functional groups — which prevent I₂ generation under photo-thermal aging — by Henan Academy of Sciences (2026). Parylene-based conformal deposited passivation layers have also been patented by Chungnam National University (2026). The Qingdao Institute of Bioenergy and Bioprocess Technology (2021) employs bifunctional polymers with side chains containing groups that passivate both positively and negatively charged grain boundary defects, significantly reducing deep-level defect concentrations.

Metal doping to reduce vacancy density and block the vacancy-mediated oxygen-to-superoxide conversion pathway is addressed in the University of Toronto’s 2021 disclosure on doped metal halide perovskites. Quantum dot surface stabilisation post-treatment specifically addressing defects arising from the ligand exchange step has been developed by DGIST (2025). According to standards bodies such as IEC and research organisations including NREL, defect density control remains the primary lever for extending perovskite solar cell operational lifetime toward the 25-year benchmarks required for commercial deployment.

Interface engineering and film quality control

White spots and efficiency losses often initiate at layer interfaces — particularly the perovskite/ETL and perovskite/HTL junctions — making interface engineering a critical complementary strategy to bulk passivation. Oxygen vacancy passivation in the SnO₂ ETL is addressed by Yonsei University (2024), 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.

Physical surface defect removal from the perovskite layer — rather than chemical passivation — 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. This yields polycrystalline films free of defect-rich surface regions with enhanced efficiency and stability. Interface modification using quasi-2D perovskite capping layers to prevent charge extraction inhomogeneity is covered by Korea University (2025), where a quasi-2D perovskite first interface modification layer is placed on the 3D perovskite photoactive layer, followed by a metal oxide second modification layer deposited by vapor, to achieve both surface defect suppression and improved energy-level alignment.

Film quality itself — particularly grain size and intrinsic defect density — is a foundational determinant of white-spot resistance. Korea Electric Power Corporation (KEPCO) has patented supersaturation-suppressed crystal growth yielding grains above 1 µm (2026) and antisolvent-assisted crystallization (2025). Pinhole suppression through controlled antisolvent application combined with ventilation is targeted specifically by Toyota Motor Corporation (2025), recognising that pinholes in the photoelectric conversion layer are a primary pathway for moisture penetration and localised degradation. Surface conversion of perovskite surfaces to insoluble wide-bandgap lead oxysalts represents another interfacial stabilisation strategy, as disclosed by NUtech Ventures (2022). Researchers publishing through Nature have highlighted that grain boundary engineering and interface passivation are now converging into unified fabrication protocols for stable perovskite modules.

Post-treatment and in-field remediation: reversing degradation after it occurs

A growing body of IP addresses reversal or mitigation of degradation that has already occurred — either during manufacturing or in-field operation — recognising that some degree of degradation is unavoidable with current processes. Hanwha Solutions Corporation has filed extensively across multiple jurisdictions on post-treatment methods specifically targeting thermally induced cell degradation during module manufacturing. Their 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, and FF.

For in-field photovoltaic modules experiencing potential-induced degradation (PID) — a closely related phenomenon involving surface polarisation and efficiency loss under operating electrical bias — Huawei Technologies has developed a signal-based remediation approach. Their US and European patents (both 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 non-invasive approach is applicable across silicon and emerging perovskite module types.

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 stabilisation post-treatment addressing defects from the ligand exchange step has been developed by DGIST (2025). Together, these post-treatment and remediation approaches signal increased recognition across the industry that corrective strategies must complement preventive ones — a shift in IP strategy that is reflected in the growing number of filings in this category. The IEA has identified perovskite module durability as a key barrier to large-scale deployment, making this category of IP commercially significant.

Patent landscape: who is leading and where the field is heading

The patent data reveals a competitive landscape concentrated among a handful of repeat filers, supplemented by academic institutions pursuing differentiated technical approaches. Hanwha Solutions Corporation is the most prolific perovskite-specific assignee in the surveyed 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 — reflecting 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, and semitransparent tandem structures, with multiple active Korean patents demonstrating a drive toward commercialisable, 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. ENI S.P.A. (with Consiglio Nazionale delle Ricerche) has built a portfolio around polyacrylic acid and polysaccharide polymer incorporation into perovskite precursor solutions, 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. A clear trend visible across the dataset is the convergence toward multi-mechanism strategies: 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. 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. Patent databases such as those maintained by EPO and WIPO reflect this acceleration in perovskite stability IP filings across all major jurisdictions.

“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.”

For R&D teams and IP professionals tracking this space, the convergence of passivation chemistry, interface engineering, film morphology control, and post-treatment into integrated manufacturing protocols represents the defining technical challenge — and competitive opportunity — in perovskite photovoltaics. The PatSnap R&D intelligence platform and IP strategy tools provide structured access to this rapidly evolving patent landscape.