SOLAR CELL CONTACTS AND METHOD OF FABRICATING SAME
A solar cell device and a method of fabricating the same is described. The solar cell includes a back contact, an absorber over the back contact, and a front contact over the absorber. The back contact includes a back electrode layer and a graphene layer.
1 . A solar cell comprising:
a back contact comprising a back electrode layer and at least one graphene layer;
an absorber over said back contact; and
a front contact over said absorber.
2 . The solar cell as in claim 1 , wherein said graphene layer is over said back electrode layer.
3 . The solar cell as in claim 1 , wherein said graphene layer is below said back electrode layer.
4 . The solar cell as in claim 1 , wherein said graphene layer has a resistivity ranging from about 10 −6 Ω·cm to about 10 −4 Ω·cm.
5 . The solar cell as in claim 1 , wherein said graphene layer has a thickness ranging from 1 nm˜100 nm.
6 . The solar cell as in claim 1 , wherein said back electrode layer comprises a metal.
7 . The solar cell as in claim 1 , wherein said back electrode layer has a resistivity ranging from about 10 −4 Ω·cm to about 10 −2 Ω·cm.
8 . The solar cell as in claim 1 , wherein said back electrode layer comprises a distributed Bragg reflector (DBR).
9 . The solar cell as in claim 1 , wherein said back electrode layer comprises a plurality of stacked distributed Bragg reflector (DBR) layers.
10 . The solar cell as in claim 9 , wherein said plurality of stacked DBR layers comprise an even number of layers ranging from 2 to 10 layers.
11 . The solar cell as in claim 9 , wherein said plurality of stacked DBR layers have an optical reflection of 80% or greater.
12 . A method for fabricating a solar cell, comprising:
forming a back contact on a substrate by depositing a back electrode layer and a graphene layer over said substrate;
forming an absorber over said back contact; and
forming a front contact over said absorber.
13 . The method as in claim 12 , wherein said back electrode layer comprises a metal having a higher resistivity than Mo.
14 . The method as in claim 12 , wherein said depositing steps are performed in a sequence comprising, in order:
(a) depositing said back electrode layer; and
(b) depositing said graphene layer over said back contact layer.
15 . The method as in claim 12 , wherein said depositing steps are performed in a sequence comprising, in order:
(a) depositing said graphene layer; and
(b) depositing said back electrode layer over said graphene layer.
16 . The method as in claim 12 , wherein said step of depositing said back electrode layer comprises depositing a plurality of distributed Bragg reflector (DBR) layers over said substrate.
17 . The method as in claim 16 , wherein said step of depositing said DBR layers comprises:
(a) depositing a first DBR material over said substrate; and
(b) depositing a second DBR material over said first DBR material.
18 . The method as in claim 17 , wherein said depositing steps (a) and (b) are repeated at least once.
19 . A method for fabricating a solar cell, comprising:
providing a substrate;
forming a back contact over said substrate by depositing a back electrode layer and a graphene layer over said substrate;
forming an absorber over said back contact;
forming a buffer over said absorber; and
forming a front contact over said buffer.
20 . The method as in claim 19 , wherein said graphene layer is in direct contact with an upper or lower surface of said back electrode layer; and
said graphene layer has a lower resistivity than said back electrode layer.