Fabrication method for interdigitated back contact photovoltaic cells
A method for manufacturing interdigitated back contact photovoltaic cells is disclosed. In one aspect, the method includes providing on a rear surface of a substrate a first doped layer of a first dopant type, and providing a dielectric masking layer overlaying it. Grooves are formed through the dielectric masking layer and first doped layer, extending into the substrate in a direction substantially orthogonal to the rear surface and extending in a lateral direction underneath the first doped layer at sides of the grooves. Directional doping is performed in a direction substantially orthogonal to the rear surface, thereby providing doped regions with dopants of a second dopant type at a bottom of the grooves. Dopant diffusion is performed to form at the rear side of the substrate one of the emitter regions and back surface field regions between the grooves and the other at the bottom of the grooves.
1. A method of manufacturing interdigitated back contact photovoltaic cells, the method comprising:
providing on a rear surface of a semiconductor substrate a first doped layer comprising a first dopant type;
providing a dielectric masking layer overlaying the first doped layer;
forming a plurality of grooves through the dielectric masking layer and the first doped layer, the plurality of grooves extending into the semiconductor substrate in a direction substantially orthogonal to the rear surface and extending in a lateral direction underneath the first doped layer at sides of the plurality of grooves;
performing a directional doping process in a direction substantially orthogonal to the rear surface, thereby providing doped regions with dopants of a second dopant type different from the first dopant type at a bottom of the plurality of grooves; and
performing a dopant diffusion process, thereby forming regions of the first dopant type in the semiconductor substrate at the rear side of the substrate and between the plurality of grooves, and further forming regions of the second dopant type in the semiconductor substrate at the bottom of the plurality of grooves.
2. The method according to claim 1 , wherein the process of forming a plurality of grooves comprises performing a dry etching process.
3. The method according to claim 1 , wherein the process of forming a plurality of grooves comprises forming grooves by laser ablation followed by a wet etching of the formed grooves.
4. The method according to claim 1 , wherein the process of forming a plurality of grooves comprises screenprinting onto the substrate a paste that selectively etches the dielectric masking layer and the first doped layer.
5. The method according to claim 1 , wherein performing a directional doping process comprises performing one of an ion implantation, a plasma doping, and a low pressure deposition with high anisotropy.
6. The method according to claim 1 , further comprising providing, before the dopant diffusion process, a second doped layer at a front side of the substrate, the second doped layer having dopants of a same dopant type as the substrate.
7. The method according to claim 1 , further comprising providing one or more of a surface passivation layer at the front side and/or the rear side of the substrate, and an antireflection coating at the front side or providing emitter contacts and base contacts at the rear side.
8. The method according to claim 7 , wherein the process of providing emitter contacts and base contacts comprises:
providing openings through the dielectric masking layer and through the first doped layer provided at the rear side to locally expose the regions of the first dopant type;
providing openings through the surface passivation layer provided at the rear side to locally expose the regions of the second dopant type;
providing the base contacts contacting the regions of the first dopant type; and
providing the emitter contacts contacting the regions of the second dopant type.
9. The method according to claim 8 , further comprising providing a metal seed layer before electroplating the emitter and base contacts.
10. The method according to claim 8 , wherein providing emitter contacts and base contacts is performed in a single metallization step.
11. The method according to claim 1 , wherein the process of forming a plurality of grooves includes forming a cantilever in the first doped layer and the dielectric masking layer at the sides of the grooves.
12. The method according to claim 1 , wherein the method does not include any lithography step.
13. The method according to claim 1 , wherein regions of the first dopant type are backside surface field regions of the photovoltaic cells and regions of the second dopant type are emitter regions of the photovoltaic cells.
14. The method according to claim 1 , wherein regions of the first dopant type are emitter regions of the photovoltaic cells and regions of the second dopant type are backside surface field regions of the photovoltaic cells.
15. A method of manufacturing interdigitated back contact photovoltaic cells, the method comprising:
forming a plurality of grooves through a first doped layer located on a rear surface of a substrate and a dielectric masking layer overlaying the first doped layer, the first doped layer comprising a first dopant type, the plurality of grooves extending into the substrate in a direction substantially perpendicular to the rear surface and extending in a direction substantially parallel to the rear surface underneath the first doped layer at sides of the plurality of grooves; and
performing a directional doping process in a direction substantially perpendicular to the rear surface so as to provide doped regions with dopants of a second dopant type different from the first dopant type at a bottom of the plurality of grooves.
16. The method according to claim 15 , further comprising performing a dopant diffusion process to form regions of the first dopant type in the substrate at the rear side of the substrate and between the plurality of grooves, and to further form regions of the second dopant type in the substrate at the bottom of the plurality of grooves.
17. The method according to claim 16 , wherein the dopant diffusion process to form the regions of the first and second dopant types are performed in a single step.
18. The method according to claim 16 , wherein the regions of the first and second dopant types are formed simultaneously.
19. The method according to claim 16 , further comprising providing, before the dopant diffusion process, a second doped layer at a front side of the substrate, the second doped layer having dopants of a same dopant type as the substrate.
20. The method according to claim 19 , wherein the dopant diffusion process also forms a front surface field, and the dopant diffusion process is performed in a single step to form the regions of the first and second dopant types and the front surface field.
21. The method according to claim 15 , wherein the grooves have a substantially rectangular shape in a plane parallel to the rear surface.