Laser processes for thin film photovoltaics

Structure setup of a thin film solar cell, showing the layers, which are separated in single steps
© Fraunhofer IWS Dresden
Structure setup of a thin film solar cell, showing the layers, which are separated in single steps
Electrical cutting of CIGS solar cells by removing the active material (P2 process, left) and the separation of the layer stack down to the substrate carrier (P1 process, right)
© Fraunhofer IWS Dresden
Electrical cutting of CIGS solar cells by removing the active material (P2 process, left) and the separation of the layer stack down to the substrate carrier (P1 process, right)

Compared to crystalline solar cells, thin film solar cells offer a flexible and simple possibility for power generation. They are continuously fabricated in a roll-to-roll procedure, which is characterized by high efficiency and low costs due to the high band velocity.

The basic setup of a thin film solar cell consists of a flexible carrier material, a metallic back contact, a photoactive material and a transparent, conductive front contact at the sun-facing side.

For the electrical wiring of single cells on the endless strip, these layers must be separated according to the electrical path.

Pulsed laser systems, particularly ultrashort pulsed lasers with lengths in the range of few 10ps to fs, can excellently perform the electrical wiring by separating the layers. Above all, ultrashort pulsed lasers are characterized by very high process velocities, a low influence zone and very small dimensions.