Laser Doped Selective Emitter
To further increase the energy conversion efficiency of silicon solar cells with boron-doped or phosphorus-doped emitter, the charge carrier recombination in the emitter region must be reduced.
Not only the charge carrier recombination in the photoactive (non-metallized) region is relevant here, but also at the metal contacts.
The doping profile requirements to achieve low charge carrier recombination are very different within these two domains.
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 lowers the cost of ownership, since complex and expensive wet-chemical processes can be dispensed with.
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.