Thin Film Solar Cell Processing

industrial laser
application note

Thin Film Solar Cell Processing


Schematic showing basic geometry and functioning of a thin film solar cell

Laser scribing of various thin film materials is a key process in manufacturing of thin film photovoltaic (PV) panels. In recent years, the PV industry has adopted the use of high-power nanosecond-pulse diode-pumped solid state (DPSS) Q-switched lasers to increase precision and throughput of scribe processes. A major push for the use of lasers is made in order to increase the quality of scribes and hence the efficiency of a solar cell while reducing fabrication costs.

A typical TFPV device consists of three layers deposited onto a glass substrate. The first layer is a conductive material; either a transparent conducting oxide (TCO) such as zinc oxide (ZnO), tin oxide (SnO2) or an opaque metallic material such as molybdenum (Mo) deposited on glass, the middle layer is the active semiconductor layer and the third layer is another conductor; either TCO, aluminium (Al) or combination of both. These three layers constitute the front-contact, the solar-absorber and the back-contact layers.

In order to generate required voltage, solar cell panels are structured by scribing parallel lines in various thin film layers. This scribing of the thin films is where DPSS Q-switched lasers are most widely applied. Typically, the following three scribe processes are performed during cell manufacturing: P1 scribe, which removes a conducting layer from the glass substrate; P2 scribe, which removes semiconductor layer from the material scribed in the P1 process; and P3 scribe, which removes all of the final electrical contact layer and some or all of the solar-absorber (P2-scribe) material. The three scribe lines are arranged parallel to one another and as closely as possible on the large flat panel.

Spectra-Physics’ short-pulse Q-switched lasers offer superior results for a variety of TF material processes and thicknesses. Depending on the material removal threshold, scribe width, and throughput requirements, a wide array of Spectra-Physics 1064 nm, 532 nm and 355 nm Q-switched product families can meet the requirements, including the Pulseo, HIPPO, Explorer, Mosaic, and Navigator lasers.