Thin film scribing is a selectivity problem: remove one layer, keep the next

Photovoltaic module interconnection requires three scribes at different depths. Getting each to stop at the right layer is where the process lives.

By LasersNews Desk·14 Jul 2026·2 min read

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Thin film photovoltaic modules are monolithically interconnected: individual cells are formed by scribing lines through the deposited layers so that adjacent cells connect in series. Three scribes are required, conventionally called P1, P2 and P3, each removing a different set of layers.

The three scribes

P1 separates the back contact layer, done after that layer is deposited and before the absorber.

P2 removes the absorber down to the back contact without cutting the contact, creating a via for interconnection.

P3 separates the front contact and absorber above the back contact, isolating adjacent cells.

Each scribe must remove specific layers and stop cleanly at the layer beneath. Cutting too deep shorts the interconnection; too shallow leaves the layer intact and the cell does not isolate.

How selectivity is achieved

Absorption difference. Layers absorb differently by wavelength. Choosing a wavelength strongly absorbed by the target layer and poorly by the layer beneath gives a degree of self-limiting behaviour.

Illumination direction. Scribing through the glass substrate rather than from the film side changes which interface receives peak intensity, and can lift a layer off from beneath rather than ablating through it.

Pulse duration. Shorter pulses confine energy, which improves selectivity between thin layers.

Fluence control. Operating just above the removal threshold for the target layer and below it for the underlying one.

The dead zone

The three scribes plus the spacing between them form a strip that generates no power — the dead zone. Its width directly reduces module efficiency, so narrowing the scribes and reducing the gaps between them is a continuous engineering objective.

That drives toward smaller spot sizes, better positioning accuracy between the three scribe steps, and tighter tolerance on scribe edge quality, since a ragged edge requires more clearance.

The production constraint

Modules are large and scribes run their full length, so throughput demands high scan speeds and often multiple parallel beams. Registration between the three scribe operations, performed at different points in the production line with the substrate moving in between, is a precision problem that determines dead zone width as much as spot size does.

It is a good illustration of a process where the laser physics has been understood for years and the engineering effort sits entirely in positioning, speed and consistency across a large area.

This article was produced by the LasersNews AI desk and reviewed by our editors.