No abstract

An elegant laser tailoring add-on process for silicon solar cells, leading to selectively doped emitters increases their efficiency h by Dh ¼ 0.5% absolute. Our patented, scanned laser doping add-on process locally increases the doping under the front side metallization, thus allowing for shallow doping and less Auger recombination between the contacts. The selective laser add-on process modifies the emitter profile from a shallow error-function type to Gaussian type and enables excellent contact formation by screen printing, normally difficult to achieve for shallow diffused emitters. The significantly deeper doping profile of the laser irradiated samples widens the process window for the firing of screen printed contacts and avoids metal spiking through the pn-junction.

A record in full area laser doped emitter solar cells with an efficiency η=18.9% is reported. Our patented, scanned laser doping process allows for the fabrication of defect free pn junctions via liquid state diffusion of predeposited dopant layers in ambient atmosphere without the need of clean room conditions. Our cells display an open circuit voltage Voc=677 mV, demonstrating laser doping to be comparable to furnace diffusion. Combining laser diffused pn junctions with a textured front side has the potential to boost the short circuit current density Jsc and thus the solar cell efficiency η to η>21%.