High throughput laser doping for selective emitter crystalline Si solar cells

One of the most promising methods to improve the efficiency of crystalline solar cells is the implementation of so-called selective emitters. This is the decoupling of the requirements for the front doping for light conversion and metallization. Underneath the contact fingers, a high doping is chosen to insure a good ohmic contact, whereas in the photoactive area a light doping is employed to reduce recombination losses and increase quantum efficiency in the short wavelength region of the device. Besides using costly and lengthy masking processes, selective emitters can be produced using lasers by means of laser doping. A laser beam with a suitable wavelength with good absorption in silicon is focused to a spot size which matches the width of the contact fingers. In this paper the process is explained, results are presented which show that the targeted effect can be achieved without detrimental “side effects”, and an optical beam splitter technology for high throughput production is proposed.