Photovoltaic device and method for manufacturing the same
Disclosed is a method to fabricate an interdigitated back contact photovoltaic device including: providing a substrate of a first-type doping being an n-type or a p-type doping; realizing on a back side a semiconducting doped structure including individual doped layers portions of the first type doping and a semiconducting doped structure of a second type; realizing a conductive layer on top of the semiconducting structure; realizing a patterned isolation resist layer having contact apertures and isolation apertures onto the conductive layer; further applying conductive pads to the contact apertures; and etching the conductive layer up to the second-type doped layer to realize trenches to electrically separate first type charge collecting structures from second type charge collecting structures. Also disclosed is an interdigitated back contact photovoltaic device as manufactured according to the disclosed method of fabrication, and a photovoltaic system including at least two interdigitated back contact photovoltaic devices.
1. A method for manufacturing an interdigitated back contact photovoltaic device including a substrate defining a plane and, parallel to said plane, a longitudinal and a lateral direction, orthogonal to said lateral direction, the method comprising:
providing a substrate of a first- or second-type doping that is an n-type or a p-type doping, the substrate having a front side and a back side, and applying a semiconducting structure on the back side, the semiconducting structure defining a front surface facing the back side of said substrate and a back surface opposite to said front surface, the semiconducting structure comprising individual doped portions of said first-type doping and a doped semiconducting structure of the second-type that is the other type than said first type, to provide alternating electrical charge-types of semiconducting contacts;
providing a conductive layer on top of said doped semiconducting structures;
applying a patterned isolation resist layer having a back surface onto said conductive layer, the formed resist layer comprising resist parts, contact apertures, and isolation apertures, the patterns of the isolation resist layer being aligned relative to said semiconducting structures;
applying a plurality of conductive pads onto said patterned isolation resist layer, so that the conductive pads fill said contact apertures making electrical contact to said conductive layer; and
etching the conductive layer in areas specified by the isolation apertures in the isolation resist layer, without extending into the semiconducting structure and creating trenches that do not extend into the semiconducting structure to form electrically separated first type charge collecting structures and second type charge collecting structures, after applying the conductive pads.
2. The method according to claim 1 , wherein said conductive layer comprises at least one transparent conductive oxide or at least one metallic layer or a combination thereof.
3. The method according to claim 2 , wherein said transparent conducting oxide layer is made of one of the oxides of the metals: Indium, Zinc, Tin, Tungsten or a combination thereof.
4. The method according to claim 2 , wherein the material of said at least one metallic layer is chosen among: Copper, Silver, Aluminium, Nickel, Zinc, Tin Chromium, Beryllium, Gold or an alloy thereof.
5. The method according to claim 1 , wherein the material of said conductive pads comprises an electrically conducting compound or paste.
6. The method according to claim 1 , further comprising applying an additional isolation layer on the back side of the photovoltaic device by filling at least the trenches.
7. The method according to claim 1 , further comprising creating a plurality of openings, defined by additional apertures in the isolation resist layer, to at least a predetermined depth in said conductive layer.
8. The method according to claim 1 , further comprising connecting the conductive pads by respective electrically conducting ribbons and/or wires.
9. An interdigitated back contact photovoltaic device having first-type charge collecting structures and second-type charge collecting structures, the photovoltaic device comprising:
a substrate of a first-type doping that is an n-type or a p-type doping, the substrate having a front side and a back side; and
a semiconducting structure applied to the back side of the substrate, the semiconducting structure defining a front surface facing the back side of said substrate and a back surface opposite to said front surface, the semiconducting structure comprising, on the back side of the substrate,
a first-type-doped semiconducting structure including a plurality of n- or p-doped portions, and
a second-type-doped semiconducting structure that is the other doped-type of said first-type-doped structure,
wherein a layer stack is arranged on said semiconducting structure, the layer stack comprising:
a conductive layer disposed on said semiconducting structures, the conductive layer including trenches provided therein, and
a patterned isolating resist layer, defining a back surface facing away from said substrate, the patterned isolating resist layer being disposed on said conductive layer, the patterned isolating resist layer comprising contact apertures, isolation apertures, and conducting pads provided on said resist layer in said contact apertures where the conducting pads electrically contact the conductive layer and jut out of the contact apertures,
wherein the trenches electrically separate the first-type charge collecting structures and the second-type charge collecting structures, said trenches being defined by said isolation apertures in the isolation resist layer, the trenches extending between said back surface to at most the back surface of said semiconducting structure and do not extend into the semiconducting structure.
10. The interdigitated back contact photovoltaic device according to claim 9 , wherein said conductive layer comprises at least one transparent conductive oxide layer or at least one metallic layer or a combination thereof.
11. The interdigitated back contact photovoltaic device according to claim 10 , wherein said trenches comprise a succession of openings of the different layers of said layer stack, said openings having lateral widths.
12. The interdigitated back contact photovoltaic device according to claim 11 , wherein the lateral width of the opening in said at least one transparent conductive oxide layer is smaller than at least one of the lateral widths of the openings of the layers of said conductive layer.
13. The interdigitated back contact photovoltaic device according to claim 10 , wherein said conductive layer comprises, on said at least one transparent conductive oxide layer, at least one metallic layer and at least one additional metallic layer, of which one is in contact with said at least one transparent conductive oxide layer, the lateral width of the aperture in said at least one additional metallic layer being smaller than the lateral width of the aperture in said at least one metallic layer.
14. The interdigitated back contact photovoltaic device according to claim 9 , wherein the semiconducting structures provide a heterojunction contact with the crystalline silicon substrate.
15. The interdigitated back contact photovoltaic device according to claim 9 , wherein the first-type-doped semiconducting structures are locally deposited on the back side of the photovoltaic device and the second-type-doped semiconducting structure is deposited on the back side of the device by at least partially covering the first-type-doped semiconducting structure, providing a tunnel-junction in the contact zones of the first- and second-type-doped semiconducting structures.
16. The interdigitated back contact photovoltaic device according to claim 9 , further comprising an additional insulating layer is deposited on the back side of the photovoltaic device, at least within the trenches.
17. The interdigitated back contact photovoltaic device according to claim 9 , further comprising a plurality of openings extending from the resist layer back surface to at least a predetermined depth in said conductive layer.
18. A photovoltaic system comprising:
at least two interdigitated back contact photovoltaic devices according to claim 9 , the at least two interdigitated back contact photovoltaic devices being interconnected by conductors,
wherein conducting pads of the first type of the first cell are connected to conducting pads of the second type of the second cell thereby establishing a series connection of accordingly connected devices, and/or
wherein conducting pads of the first or second type of the first cell are connected respectively to conducting pads of the first or second type of the second cell thereby establishing a parallel connection of accordingly connected devices.
19. The method according to claim 2 , wherein the material of said conductive pads comprises an electrically conducting compound or paste.
20. The method according to claim 3 , wherein the material of said conductive pads comprises an electrically conducting compound or paste.