PHOTOVOLTAIC CELL AND METHODS FOR PRODUCING A PHOTOVOLTAIC CELL
A photovoltaic cell ( 10 ) is fabricated by depositing a first transparent conductive layer ( 12 ) onto a substrate carrier ( 11 ). Portions of the first transparent conductive layer ( 12 ) are selectively removed to form a plurality of discrete transparent conductive protruding regions ( 13 ) or a plurality of discrete indentations ( 27 ) in the first transparent conductive layer ( 12 ). A silicon layer ( 14 ) comprising a charge separating junction is deposited onto the plurality of discrete protruding regions ( 13 ) or onto the plurality of discrete indentations ( 27 ) by chemical vapour deposition. A second transparent conductive layer ( 15 ) is deposited on the silicon layer ( 14 ) by chemical vapour deposition.
1 . A method of fabricating a photovoltaic cell ( 10 ; 10 ′) comprising:
providing a substrate carrier ( 11 ; 11 ′),
depositing a first transparent conductive layer ( 12 ; 12 ′) onto the substrate carrier ( 11 ; 11 ′),
selectively removing portions of the first transparent conductive layer ( 12 ) and forming a plurality of discrete transparent conductive protruding regions ( 13 ), or selectively removing portions of the first transparent conductive layer ( 12 ′) and forming a plurality of discrete indentations ( 27 ) in the first transparent conductive layer ( 12 ′),
depositing a silicon layer ( 14 ; 14 ′) comprising a charge separating junction onto the plurality of discrete protruding regions ( 13 ) or onto the plurality of discrete indentations ( 27 ) by chemical vapour deposition, and
depositing a second transparent conductive layer ( 15 ; 15 ′) on the silicon layer ( 14 ; 14 ′) by chemical vapour deposition.
2 . The method according to claim 1 , wherein
the silicon layer ( 14 ; 14 ′) is deposited by plasma enhanced chemical vapour deposition.
3 . The method according to claim 1 or claim 2 , wherein the first transparent conductive layer ( 12 ; 12 ′) and/or the second transparent conductive layer ( 15 ; 15 ′) is deposited by low pressure chemical vapour deposition.
4 . The method according to one of claims 1 to 3 , wherein the silicon layer ( 14 ; 14 ′) is deposited conformally onto the plurality of discrete transparent conductive protruding regions ( 13 ) or onto the plurality of discrete indentations ( 27 ).
5 . The method according to one of claims 1 to 4 , wherein the second transparent conductive layer ( 15 ; 15 ′) is deposited conformally onto the silicon layer ( 14 ; 14 ′).
6 . The method according to one of claims 1 to 5 , wherein the portions of the first transparent conducive layer ( 12 ) are selectively removed to form a closed sub-layer ( 17 ) from which the plurality of discrete transparent conductive protruding regions ( 13 ) extend, the plurality of discrete transparent conductive protruding regions ( 13 ) comprising material of the first transparent conductive layer ( 12 ).
7 . The method according to claim 6 , wherein
the silicon layer ( 14 ) is deposited conformally onto the sub-layer ( 17 ) and onto the plurality of the discrete transparent conductive protruding regions ( 13 ).
8 . The method according to one of claims 1 to 6 , wherein the portions of the first transparent layer ( 12 ) are removed to produce the plurality of discrete transparent conductive protruding portions ( 13 ) with a diameter in the range of 150 nm to 200 nm and a height of 500 nm to 700 nm, or the portions of the first transparent layer ( 12 ′) are removed to produce the plurality of discrete indentations ( 27 ) with a diameter in the range of 150 nm to 200 nm and a height of 500 nm to 700 nm.
9 . The method according to claim 8 , wherein
after deposition of the silicon layer ( 14 ; 14 ′), an outer surface of the silicon layer ( 14 ; 14 ′) comprises a plurality of protruding regions having a diameter of at least 300 nm.
10 . The method according to one of claims 1 to 9 , wherein the second transparent conductive layer ( 15 ; 15 ′) fills regions between adjacent protruding regions comprising silicon or fills indentations lined with silicon.
11 . The method according to one of claims 1 to 10 , wherein the first transparent conductive layer ( 12 ; 12 ′) is structured by reactive ion etching or electron beam lithography to produce the plurality of discrete transparent conductive protruding regions ( 13 ) or the plurality of discrete indentations ( 27 ).
12 . The method according to one of claims 1 to 11 , wherein a plurality of discrete metal islands ( 23 ) are deposited on the first transparent conductive layer ( 12 ) and regions of the first transparent conductive layer ( 12 ) outside of the metal islands are removed by selective etching to produce a plurality of discrete protruding regions ( 13 ) comprising material of the first transparent conductive layer ( 12 ).
13 . Method according to one of claims 1 to 11 , wherein
a patterned resist layer is deposited on the first transparent conductive layer ( 12 ) and the first transparent conductive layer ( 12 ) is selectively etched to produce the plurality of discrete indentations ( 27 ) in the first transparent conductive layer ( 12 ).
14 . A photovoltaic cell ( 10 ; 10 ′) comprising:
a substrate carrier ( 11 ; 11 ′);
a first transparent conductive layer ( 12 ; 12 ′) positioned on the substrate carrier ( 11 ; 11 ′) comprising
a plurality of discrete transparent conductive protruding regions ( 13 ), the plurality of discrete transparent conductive protruding regions ( 13 ) having a diameter in the range of 150 nm to 200 nm and a height of 500 nm to 700 nm, or
a plurality of discrete indentations ( 27 ) having a diameter in the range of 150 nm to 200 nm and a height of 500 nm to 700 nm,
a silicon layer ( 14 ; 14 ′) comprising a charge separating junction covering the plurality of discrete transparent conductive protruding regions ( 13 ) or the plurality of discrete indentations ( 27 ), and
a second transparent conductive layer ( 15 ; 15 ′) positioned on the silicon layer ( 14 ; 14 ′).
15 . The photovoltaic cell according to claim 14 , wherein the silicon layer ( 14 ; 14 ′) is positioned conformally on the plurality of discrete transparent conductive protruding regions ( 13 ) or on the plurality of discrete indentations ( 27 ).
16 . The photovoltaic cell according to claim 14 or claim 15 , wherein the silicon layer ( 14 ; 14 ′) comprises a plurality of protrusions having a diameter of 300 nm or greater.
17 . The photovoltaic cell according to one of claims 14 to 16 , wherein
the second transparent conductive layer ( 15 ; 15 ′) is positioned conformally on the silicon layer ( 14 ; 14 ′).
18 . The photovoltaic cell according to one of claims 14 to 17 , wherein the plurality of discrete transparent conductive protruding regions ( 13 ) or plurality of discrete indentations ( 27 ) extend generally perpendicular to a major plane ( 18 ) of the substrate carrier ( 11 ; 11 ′).
19 . The photovoltaic cell according to one of claims 14 to 18 , wherein the second transparent conductive layer ( 15 ; 15 ′) fills regions between protruding regions of the silicon layer ( 14 ; 14 ′).