The tracked dataset contains 20 patent families that specifically combine tandem or multijunction solar cell architecture with surface, field-effect or defect passivation claim language, covering 2015 through the 2026 data cut-off. This is a narrow intersection of a much larger tandem solar cell patent universe, since most tandem filings address passivation as one element of a broader cell-structure claim rather than as a standalone invention. Anyone benchmarking total tandem cell IP activity should treat this 20-family figure as a specific subset, not the full picture.

Filing volume peaked at 4 families in 2022 and has not exceeded that level since, which reads as flat rather than accelerating. That said, publication typically lags filing by around 18 months, so the most recent one to two years in any trend chart are structurally undercounted and should not be read as a hard slowdown yet. The honest read is that this sub-field has not shown sustained growth through the last confirmed peak, and the next 12–18 months of publications will clarify whether that changes.

The assignee set spans vertically integrated solar manufacturers, a Dutch applied-science research organisation, and at least one aerospace company, reflecting how passivation know-how in this niche has migrated in from adjacent high-reliability cell work as well as mainstream PV suppliers. None of the tracked assignees show filings in the most recent year, so there is currently no single visible momentum leader. The concentration ranking itself is the more reliable indicator of who has built the deepest position historically.

US20150040972A1, assigned to SolAero Technologies Corp. and published in 2015, claims an inverted metamorphic multijunction solar cell with sulfur passivation specifically on the surface of the contact layer. That narrows its blocking effect to inverted metamorphic architectures using sulfur-based contact-layer passivation rather than passivation approaches generally, so tandem cells using other passivation chemistries or non-inverted structures sit outside its core claim scope. Anyone designing around it should confirm whether their stack uses an inverted metamorphic structure and a sulfur-based treatment before assuming freedom to operate.

The IPC composition shows the dataset is almost entirely H01L semiconductor-device claims, with only a small H01G capacitor-adjacent cluster of 4 records and a single H10K organic-semiconductor record. That thin crossover into capacitor-integrated passivation contacts and organic or perovskite interface passivation suggests these branches carry lower claim density relative to the mainstream device-structure filings. A first claim written around field-effect passivation for inverted metamorphic stacks, or around passivation chemistries other than sulfur-based contact treatments, would currently face less crowded prior art than a straightforward H01L device-structure claim.