Selective Emitter and Texture Processes for Back Contact Solar Cells
Methods for manufacturing textured selective emitter back contact solar cells, and solar cells made in accordance therewith. A separate antireflective coating is preferably deposited, which also preferably provides simultaneous hydrogen passivation. The high sheet resistance and low sheet resistance selective emitter diffusions may be performed in either order.
1 . A method for manufacturing a back contact solar cell, the method comprising the steps of:
texturing a front surface of the solar cell;
performing a first emitter diffusion;
depositing a barrier layer on the front surface;
removing at least a portion of the first emitter diffusion from a rear surface of the solar cell;
performing a second emitter diffusion in a desired pattern on the rear surface;
removing the barrier layer from the front surface; and
depositing an antireflective coating on the front surface.
2 . The method of claim 1 wherein the first emitter diffusion provides a higher sheet resistance than the second emitter diffusion.
3 . The method of claim 1 wherein one or both depositing steps are performed using Plasma Enhanced Chemical Vapor Deposition (PECVD).
4 . The method of claim 3 wherein the barrier layer and/or the antireflective coating comprise SiN.
5 . The method of claim 1 wherein one or both depositing steps further comprise providing simultaneous hydrogen passivation.
6 . The method of claim 1 wherein the barrier layer comprises a different material than the antireflective coating.
7 . A back contact solar cell comprising:
a textured front surface;
a front side emitter comprising a first sheet resistance;
a back side emitter comprising a second sheet resistance lower than said first sheet resistance; and
an antireflective coating comprising an index of refraction of greater than approximately 2.01.
8 . The back contact solar cell of claim 7 wherein said antireflective coating comprises PECVD-deposited SiN.
9 . The back contact solar cell of claim 7 comprising a surface recombination velocity of less than 1000 cm/s.
10 . The back contact solar cell of claim 9 comprising a surface recombination velocity of less than 15 cm/s.
11 . The back contact solar cell of claim 10 comprising a surface recombination velocity of less than 1 cm/s.
12 . The back contact solar cell of claim 7 wherein said front side emitter comprises a depth of less than approximately 0.35 microns.
13 . A method for manufacturing a back contact solar cell, the method comprising the steps of:
performing a first emitter diffusion on a rear side of the solar cell;
subsequently performing a second emitter diffusion on the rear side and a front side of the solar cell, the second emitter diffusion providing a higher sheet resistance than the first emitter diffusion.
14 . The method of claim 13 further comprising the steps of:
texturing a front surface of the solar cell and depositing a barrier layer on the front surface prior to performing the first emitter diffusion;
removing the barrier layer after performing the first emitter diffusion and before performing the second emitter diffusion; and
depositing an antireflective coating on the front surface after performing the second emitter diffusion.
15 . The method of claim 14 wherein one or both depositing steps are performed using Plasma Enhanced Chemical Vapor Deposition (PECVD).
16 . The method of claim 15 wherein the barrier layer and/or the antireflective coating comprise SiN.
17 . The method of claim 14 wherein one or both depositing steps further comprise providing simultaneous hydrogen passivation.
18 . The method of claim 14 wherein the barrier layer comprises a different material than the antireflective coating.