The dataset shows filings climbing to a peak of 18 in 2020 before falling to 6 by the 2022 midpoint. This typically happens when a field's foundational structural problems — in this case light extraction and quantum-well design — get solved by an initial wave of filers, after which competitors shift to smaller iterative claims rather than filing new foundational patents. It does not necessarily mean interest in UV-C LEDs is declining; it more likely means the core architecture has stabilised. Because publication lags filing by around 18 months, the very last one to two years of any trend will always look thinner than they eventually turn out to be, so some of the apparent decline may still be an artefact of reporting lag.

Co-filing data shows a small cluster of closely linked assignees sharing the densest claim space, with the strongest co-assignee pairs each covering 29 to 31 shared records. This pattern is more typical of coordinated equipment, materials and research-institute partners filing together than of independent competitors racing each other. A full assignee ranking table, built from the same 87-family dataset, sits alongside this analysis and should be checked directly rather than inferred from citation counts alone, since citation leaders and filing-volume leaders are not always the same organisations.

External quantum efficiency measures how much of the light generated inside a UV-C LED chip actually escapes and becomes usable output, and it is one of the three defining terms this dataset was built around alongside wall-plug efficiency and light extraction. Patent claims addressing it typically target specific physical structures — photonic-crystal layers, reflecting electrode geometries, layer-thickness limits — rather than the efficiency outcome itself, since efficiency numbers are not directly patentable. Anyone drafting in this space should expect examiners to focus on the structural mechanism claimed, not the efficiency percentage cited in the specification.

Relative to the dense core of vertical-chip fabrication and AlGaN epitaxial structure claims, several adjacent branches show thinner filing density in this dataset: photonic-crystal void geometry variants, sub-100nm p-AlGaN thickness and transparency tuning, and non-vertical chip light-extraction architectures. These are not unclaimed fields, but they carry noticeably fewer records than the core structural claims that dominate the top-cited patents. A first filing in these branches should focus on a specific, narrow structural variant rather than a broad efficiency-outcome claim, since the surrounding prior art is thinner but not absent.

China accounts for 48 of the 87 tracked records, well ahead of the EPO (17), the US (13) and all other venues combined. This concentration reflects where the manufacturing and component-supply base for deep-UV LEDs and their epitaxial equipment is heavily located, which drives both defensive and offensive filing there. For freedom-to-operate purposes, this means Chinese-language prior art and Chinese patent examiners' prior rejections should be weighted more heavily than in fields where US or European filing dominates.