Strong oxide transport layer with clusters and gap fill layer
Transport layers with clusters and a gap fill layer are described. In an embodiment, a solar cell includes a hole transport layer, a perovskite absorber layer and an electron transport layer. In such an embodiment, the electron transport layer includes clusters and a gap fill layer to improve the overall cohesion and mechanical strength of the transport layer while also maintaining good electrical performance.
1 . A solar cell comprising:
a substrate;
a first transport layer over the substrate;
an absorber layer over the first transport layer; and
a second transport layer over the absorber layer;
wherein the second transport layer comprises fullerene-containing transport clusters and an alumina gap fill layer that is grown between the fullerene-containing transport clusters and over a portion of the fullerene-containing transport clusters such that the alumina gap fill layer is thicker between the fullerene-containing transport clusters than over the fullerene-containing transport clusters.
2 . The solar cell of claim 1 , wherein the substrate comprises a silicon subcell.
3 . The solar cell of claim 1 , wherein the absorber layer comprises perovskite.
4 . The solar cell of claim 1 , wherein some of the fullerene-containing transport clusters are characterized by a height that is greater than an average layer thickness of the alumina gap fill layer.
5 . The solar cell of claim 1 , wherein the fullerene-containing transport clusters comprise fullerene blended with a metal halide.
6 . The solar cell of claim 1 , wherein a buffer layer is formed over the second transport layer.
7 . The solar cell of claim 6 , wherein the buffer layer comprises a metal oxide.
8 . The solar cell of claim 7 , wherein the fullerene-containing transport clusters provide a charge path between the absorber layer and the buffer layer.
9 . The solar cell of claim 1 , wherein a top portion of the fullerene-containing transport clusters is not completely covered by the gap fill material.
10 . The solar cell of claim 9 , further comprising a buffer layer over the second transport layer, wherein the buffer layer is in direct contact with the top portion of the fullerene-containing transport clusters.
11 . The solar cell of claim 1 , wherein the fullerene-containing transport clusters and the alumina gap fill layer, in combination, provide complete coverage of a top surface of the absorber layer.
12 . A method for processing a solar cell comprising:
forming a first transport layer over a substrate;
forming an absorber layer over the first transport layer; and
forming a second transport layer over the absorber layer, wherein forming the second transport layer includes:
depositing a fullerene-containing transport material on a top surface of the absorber layer, the fullerene-containing transport material forming fullerene-containing transport clusters along the top surface of the absorber layer; and
growing an alumina gap fill layer between the fullerene-containing transport clusters and over a portion of the fullerene-containing transport clusters such that the alumina gap fill layer is thicker between the fullerene-containing transport clusters than over the fullerene-containing transport clusters.
13 . The method of claim 12 , wherein the substrate comprises a silicon subcell.
14 . The method of claim 12 , wherein the absorber layer comprises perovskite.
15 . The method of claim 12 , wherein the fullerene-containing transport material is deposited with a thermal evaporation technique.
16 . The method of claim 12 , wherein the alumina gap fill layer is grown with atomic layer deposition.
17 . The method of claim 12 , wherein the fullerene-containing transport clusters and the alumina gap fill layer, in combination, provide complete coverage of the top surface of the absorber layer.
18 . The method of claim 12 , further comprising forming a buffer layer over the second transport layer, the buffer layer comprising a metal oxide.
19 . The method of claim 18 , where the transport clusters provide a charge path between the absorber layer and the buffer layer.