Laser Doped Selective Emitter (LDSE )
To further increase the energy conversion efficiency of silicon solar cells with boron-doped or phosphorus-doped emitters, the charge carrier recombination in the emitter region must be reduced.
For this purpose, not only the charge carrier recombination in the photoactive (non-metallized) region is relevant, but also at the metal contacts.
The requirements for the doping profile to achieve a low charge carrier recombination are very different within these two areas.
Solution to form differently doped emitter regions:
Use of the so-called selective emitter approach: higher doping under the metal contacts is therefore achieved by driving additional boron or phosphorus atoms from the borosilicate glass (BSG) or phosphosilicate glass (PSG) layer formed during boron or phosphorus diffusion by means of laser diffusion.
Laser doped selective emitters (LDSE) reduce the contact resistance through selective overdoping of the contact areas. The process solution achieves highest alignment accuracies down to 10 µm, an extremely homogenous energy distribution through mask imaging with beam sizes from 100 - 300 µm.
Advantages of the LDSE process:
Compared to selective etching processes, the laser offers the possibility of free programmability of the doping geometry. Furthermore, laser processing reduces the cost of ownership, since it eliminates the need for complex and expensive wet chemical processes.