Solar cell

1 . A solar cell comprising:

a substrate having a front surface configured to face a light source in use, and a rear surface opposite the front surface, the front surface having a front surface morphology and the rear surface having a rear surface morphology, wherein the front and rear surface morphologies are configured such that the front surface has a greater surface area than the rear surface;

an emitter arranged on the rear surface of the substrate;

a reflector layer arranged on the rear surface of the substrate, the reflector layer comprising a first sub-layer having a first refractive index and a second sub-layer having a second refractive index that is greater than the first refractive index, and wherein the first sub-layer is rearward of the second sub-layer; and

wherein the first sub-layer comprises a dielectric film, and wherein the second sub-layer comprises a transparent conductive oxide.

2 . A solar cell according to claim 1 wherein the front surface morphology comprises a texture.

3 . A solar cell according to claim 1 , wherein the rear surface morphology is smooth and planar.

4 . A solar cell according to claim 1 , wherein the rear surface morphology comprises a polished texture.

5 . A solar cell according to claim 1 , wherein a surface roughness of the front surface of the substrate is greater than a surface roughness of the rear surface of the substrate.

6 . A solar cell according to claim 1 , wherein the rear surface of the substrate is configured to have a greater weighted average reflection than the front surface of the substrate for wavelengths between 400 nm and 1000 nm.

7 . A solar cell according to claim 6 , wherein the rear surface of the substrate is configured to have a weighted average reflection that is greater than 13%.

8 . A solar cell according to claim 1 , wherein an interface layer is provided between the emitter and the rear surface of the substrate.

9 . A solar cell according to claim 1 wherein the first sub-layer comprises silicon oxynitride.

10 . A solar cell according to claim 1 , wherein the reflector layer comprises a third sub-layer comprising a transparent metal oxide (TMO).

11 . A solar cell according to claim 1 , the solar cell being a heterojunction solar cell.

12 . A solar cell according to claim 1 , wherein the front surface morphology comprises a pyramid texture.

13 . A solar cell according to claim 12 , wherein the rear surface morphology comprises a pyramid texture.

14 . A solar cell as claimed in claim 13 , wherein a slope angle of a plurality of pyramids of the rear surface morphology is less than a slope angle of a plurality of pyramids of the front surface morphology.

15 . A solar cell as claimed in claim 14 , wherein the slope angle of the plurality of pyramids of the rear surface morphology is between about 40% to 60% of the slope angle of the plurality of pyramids of the front surface morphology, and optionally wherein the slope angle of the plurality of pyramids of the rear surface morphology is about 50% of the slope angle of the plurality of pyramids of the front surface morphology.

16 . A solar cell as claimed in claim 1 , wherein the first sub-layer has a refractive index of less than 1.8 for a wavelength of 633 nm, and optionally wherein the first sub-layer has a refractive index of between 1.3 and 1.7 for a wavelength of 633 nm, and optionally wherein the first sub-layer has a refractive index of between 1.4 and 1.6 for a wavelength of 633 nm.

17 . A solar cell as claimed in claim 16 , wherein the second sub-layer has a refractive index greater than or equal to 1.8 for a wavelength of 633 nm, and optionally wherein the second sub-layer has a refractive index of between 1.8 and 2.2 for a wavelength of 633 nm, and optionally wherein the second sub-layer has a refractive index of between 1.9 and 2.1 for a wavelength of 633 nm.

18 . A solar cell as claimed in claim 1 , wherein the first sub-layer comprises silicon oxynitride and the second sub-layer comprises one of: indium tin oxide; indium zinc oxide; aluminum zinc oxide; and indium tungsten oxide.

19 . A solar cell comprising:

a substrate having a front surface configured to face a light source in use, and a rear surface opposite the front surface, the front surface having a front surface morphology and the rear surface having a rear surface morphology, wherein the front and rear surface morphologies are configured such that the front surface has a greater surface area than the rear surface;

an emitter arranged on the rear surface of the substrate;

a reflector layer arranged on the rear surface of the substrate, the reflector layer comprising a first sub-layer having a first refractive index and a second sub-layer having a second refractive index that is greater than the first refractive index, and wherein the first sub-layer is rearward of the second sub-layer; and

wherein the front surface morphology comprises a pyramid texture;

wherein the rear surface morphology comprises a pyramid texture; and

wherein a slope angle of a plurality of pyramids of the rear surface morphology is less than a slope angle of a plurality of pyramids of the front surface morphology.

20 . A solar cell as claimed in claim 19 , wherein the slope angle of the plurality of pyramids of the rear surface morphology is between about 40% to 60% of the slope angle of the plurality of pyramids of the front surface morphology, and optionally wherein the slope angle of the plurality of pyramids of the rear surface morphology is about 50% of the slope angle of the plurality of pyramids of the front surface morphology.