Filing has slowed substantially from its 2017 peak of 118 families to single digits in the most recent tracked year, with a 2022 midpoint of only 29. That does not mean PERC is abandoned commercially — it remains a widely deployed cell architecture — but the patent record shows the core device claims are largely staked out, and new filing activity is now concentrated on incremental process improvements rather than foundational architecture. Anyone filing new PERC claims today is working in a much more crowded prior-art environment than an applicant in 2017 was.

Ownership in this dataset clusters around a small group of related Chinese entities, most visibly a set of regional Aiko subsidiaries that co-file extensively — one pair alone shares 120 families. Several Tongwei entities and other major Chinese cell manufacturers also appear prominently. This concentration reflects how PERC commercialization itself was concentrated among a handful of large-scale Chinese manufacturers during the technology's adoption phase.

A selective emitter creates heavier doping directly under the metal contact fingers and lighter doping elsewhere on the cell surface, which reduces contact resistance losses while preserving surface passivation quality across the rest of the emitter. It is one of the most heavily cited technical routes in this dataset — the top-cited record specifically addresses selective emitter formation on double-sided PERC cells. Because it is a well-documented technique with dense prior art, new filings in this specific area need to differentiate carefully on process detail, such as the doping profile or laser method used.

Filing density is thin, relative to the core semiconductor device classifications, in areas like coating and surface deposition, crystal growth, and module-level photovoltaic integration under H02S — each represented by a fraction of the 478 total families. These branches sit adjacent to the heavily claimed rear passivation and selective emitter architecture but have not attracted the same volume of filing. That gap does not guarantee patentability, but it does mean the prior-art density an applicant must clear is lower there than in the core device claims.

Yes — 345 of the 478 tracked filings entered through the Chinese patent office, compared with 38 in the United States, 33 at the EPO, 22 via the PCT route and 21 in India. For a manufacturer sourcing cells or equipment from Chinese suppliers, or manufacturing within China, this means the bulk of enforceable claim scope on PERC efficiency techniques sits under Chinese patent law. Freedom-to-operate work focused only on US or European filings would miss most of the actual claim density in this field.