In this dataset, a bifacial PERC filing is one whose claims combine passivated emitter and rear contact structure with language specific to dual-side light collection, such as rear-side collection, bifaciality factor, or bifacial module construction. It is not enough for a filing to mention PERC and separately mention a bifacial module; the claims need to tie the rear-contact structure to the rear-side light-harvesting function. That combination requirement is why the tracked set is only 52 families despite PERC itself being a widely patented base technology.

One co-filing relationship dominates: two related entities, Zhejiang Aiko Solar Energy Technology Co., Ltd. (Zhejiang Aiko Solar Energy Technology) and Guangdong Aiko Technology Co., Ltd. (Guangdong Aiko Technology), appear together on 45 of the 52 families in this dataset. No other assignee approaches that concentration. A handful of other named assignees, including TP Solar, hold smaller numbers of filings, with TP Solar showing the only filing recorded in the most recent year tracked.

Filing volume peaked in 2018 at 23 families and has declined in most years since, including a year with zero recorded filings at the 2022 midpoint. That trajectory suggests the core structural approaches to bifacial PERC were staked out early and later activity has shifted toward narrower refinements. Because publication lags filing by roughly 18 months, the very latest years in any dataset will always look thinner than they eventually turn out to be, so the recent taper should be read with that caveat rather than taken as proof the field is dormant.

The clearest gaps sit outside core cell architecture: conductive ink formulations for rear-side grids, coatings and glazing compositions for the rear glass, and interconnection cabling for bifacial arrays each register only two records in this dataset against 52 total families. Cell-level structural claims under H01L are comprehensively covered, but claims focused on materials, coatings, and module-level interconnection have far less prior art density and are worth scoping first for new filings.

US20200381572A1 describes a bifacial punched PERC solar cell with a light-transmitting region formed by laser grooving through the rear passivation layer, connecting the rear aluminium finger to the P-type silicon. Its claims are specific to that punched, light-transmitting rear architecture rather than to bifacial PERC cells generally, so it constrains designs that use a comparable laser-grooved through-hole approach more than it blocks bifacial PERC design broadly. Filed by Guandong Aiko Solar Energy Technology, it sits within the same co-filing group that holds the large majority of families in this dataset, so a full review of that group's related filings is the right next step before finalising a design that uses a similar punched-cell concept.