Fabrication of solar cells with counter doping prevention
A solar cell fabrication process includes printing of dopant sources over a polysilicon layer over backside of a solar cell substrate. The dopant sources are cured to diffuse dopants from the dopant sources into the polysilicon layer to form diffusion regions, and to crosslink the dopant sources to make them resistant to a subsequently performed texturing process. To prevent counter doping, dopants from one of the dopant sources are prevented from outgassing and diffusing into the other dopant source. For example, phosphorus from an N-type dopant source is prevented from diffusing to a P-type dopant source comprising boron.
1. A method of fabricating a solar cell, the method comprising:
forming a layer of polysilicon over a backside of a solar cell substrate, the solar cell substrate having a front side facing the sun to receive solar radiation during normal operation, the backside opposite the front side;
printing a first dopant source over the layer of polysilicon, the first dopant source comprising printable inks;
curing the first dopant source to diffuse dopants from the first dopant source to the layer of polysilicon to form a first diffusion region in the layer of polysilicon;
preventing counterdoping of dopants from the first dopant source to a second dopant source during the curing of the first dopant source, wherein preventing counterdoping of dopants from the first dopant source to the second dopant source comprises purging dopants from the first dopant source out of a chamber during the curing of the first dopant source; and
texturing a surface formed over the front side of the solar cell substrate.
2. The method of claim 1 wherein the curing of the first dopant source also cures the second dopant source to diffuse dopants from the second dopant source to form a second diffusion region in the layer of polysilicon.
3. The method of claim 1 wherein purging dopants from the first dopant source out of the chamber during the curing of the first dopant source comprises:
flowing an inert gas through the chamber.
4. The method of claim 1 wherein purging dopants from the first dopant source out of the chamber during the curing of the first dopant source comprises:
curing the first dopant source in a chamber under vacuum.
5. The method of claim 1 wherein the first and second dopant sources are printed by inkjet printing.
6. The method of claim 1 wherein the first and second dopant sources are printed in one pass of an inkjet printing process.