Nanostructured CIGS Absorber Surface for Enhanced Light Trapping
A technique includes fabricating a layered precursor including: depositing a first film including a first indium gallium selenide compound on a substrate; then depositing a second film including a CuSe compound; then heating the substrate, the first film and the second film to convert the CuSe compound in the second film to a Cu 2-x Se (0.2=≦x≦1) compound; then reactively depositing a third film including a second indium gallium selenide compound to convert the first film, the second film and the third film into a CIGS absorber film; and forming nanoscale morphological asymmetries in the CIGS absorber film, wherein a surface portion of the CIGS absorber film has a distribution of grain sizes with gaps between most of their surface area characterized by reentrant angles which effectively trap light.
1 . A method, comprising:
fabricating a layered precursor including:
depositing a first film including a first indium gallium selenide compound on a substrate; then
depositing a second film including a CuSe compound; then
heating the substrate, the first film and the second film to convert the CuSe compound in the second film to a Cu 2-x Se (0.2=<x<1) compound; then
reactively depositing a third film including a second indium gallium selenide compound to convert the first film, the second film and the third film into a CIGS absorber film; and
forming nanoscale morphological asymmetries in the CIGS absorber film,
wherein a surface portion of the CIGS absorber film has a distribution of grain sizes with gaps between most of their surface area characterized by reentrant angles which effectively trap light.
2 . The method of claim 1 , wherein forming nanoscale morphological asymmetries in the CIGS absorber film includes Cu—Se flux-assisted re-crystallization.
3 . The method of claim 2 , wherein Cu—Se flux-assisted re-crystallization includes coalescence and coarsening of both CIGS grains and voids formed there between by reactive mass transport.
4 . The method of claim 1 , wherein forming includes rapid optical processing.
5 . The method of claim 1 , wherein forming includes rapid isothermal processing.
6 . The method of claim 1 , further comprising depositing a cap film on the third film, the cap film including Se.
7 . The method of claim 6 , wherein the cap film includes Se 1-s S s with optional Na, where 0≦s≦1.
8 . The method of claim 1 , further comprising depositing a buffer film on the CIGS absorber film.
9 . The method of claim 8 , wherein depositing the buffer film includes at least one member selected from the group consisting of chemical bath deposition and atomic layer deposition.
10 . The method of claim 8 , further comprising depositing a transparent resistive oxide on the buffer film.
11 . The method of claim 10 , wherein depositing the transparent resistive oxide includes at least one member selected from the group consisting of chemical bath deposition and atomic layer deposition.
12 . A composition of matter, comprising a GIGS absorber film including nanoscale morphological asymmetries in the CIGS absorber film, wherein a surface portion of the CIGS absorber film has a distribution of grain sizes with gaps between most of their surface area characterized by reentrant angles which effectively trap light.
13 . The composition of matter of claim 12 , further comprising a buffer film coupled to the GIGS absorber film.
14 . The composition of matter of claim 12 , further comprising a transparent resistive oxide coupled to the buffer film.
15 . An apparatus, comprising a CIGS absorber film including nanoscale morphological asymmetries in the CIGS absorber film, wherein a surface portion of the CIGS absorber film has a distribution of grain sizes with gaps between most of their surface area characterized by reentrant angles which effectively trap light.
16 . The apparatus of claim 15 , further comprising a buffer film coupled to the CIGS absorber film.
17 . The apparatus of claim 16 , further comprising a transparent resistive oxide coupled to the buffer film.
18 . The apparatus of claim 17 , wherein the transparent resistive oxide include amorphous zinc tin oxide.
19 . A solar cell module, comprising the apparatus of claim 15 .