Transparent solar cell for an electronic device and method for manufacturing said solar cell
A solar cell for an electronic device including a substrate made of a transparent material to be exposed to incident light, a first electrode made of transparent electrically conductive material, formed on one face of the substrate and including an inner face opposite an outer face oriented towards the substrate, the inner face including a first portion having a roughness greater than the roughness of a second portion, an absorbent layer extending by an outer face over the first portion of the inner face of the first electrode, a second electrode made of an electrically conductive material and extending over an inner face of the absorbent layer opposite the outer face of the latter, the absorbent layer and the second electrode being perforated to delimit blind cavities, the bottom of each being formed by the second portion of the inner face of the first electrode.
1 . A solar cell that is part of an electronic device, wherein the solar cell comprises:
a substrate made of a transparent material to be exposed to incident light,
a first electrode made of transparent electrically conductive material, formed on one face of the substrate and comprising an inner face opposite an outer face oriented towards the substrate, said inner face comprising a first portion and a second portion, the first portion having a roughness greater than a roughness of a second portion of the inner face, wherein the second portion of the inner face of the first electrode has a polished surface finish configured to transmit the incident light without scattering,
an absorbent layer extending by an outer face over the first portion of the inner face of the first electrode, and
a second electrode made of an electrically conductive material and extending over an inner face of the absorbent layer opposite the outer face of the absorbent layer,
the absorbent layer and the second electrode being perforated so as to delimit a plurality of blind cavities, with the first electrode not being perforated, wherein a bottom of each blind cavity of the blind cavities is formed by the second portion of the inner face of the first electrode having the roughness different from that of the first portion.
2 . The solar cell according to claim 1 , wherein the first electrode has a thickness between 0.5 and 5 μm.
3 . The solar cell according to claim 1 , wherein the absorbent layer has a thickness between 100 nm and 1 μm.
4 . The solar cell according to claim 1 , wherein the first and second electrodes are made of transparent conductive oxides.
5 . The solar cell according to claim 4 , wherein the first and second electrodes are made of zinc oxide, tin oxide, or indium tin oxide.
6 . The solar cell according to claim 1 , further comprising a transparent protective layer covering the second electrode and filling each blind cavity.
7 . The solar cell according to claim 6 , wherein the material of the protective layer has a refractive index between 1 and 2.
8 . The solar cell according to claim 6 , wherein the protective layer is made of parylene, polyimide, siloxane, a nitride, or an oxide.
9 . The solar cell according to claim 1 , wherein the substrate is formed by a stack of layers comprising a support layer and an intermediate layer, the intermediate layer being interposed between the support layer and the first electrode and being configured so as to have a refractive index between 1.6 and 1.9.
10 . A timepiece, including a case comprising a middle part, a glass, and a back defining an internal volume in which a horological movement is housed, wherein said timepiece further comprises the solar cell according to claim 1 , configured to supply electrical energy to the horological movement.
11 . The timepiece according to claim 10 , wherein the solar cell is fixed to the glass so that the substrate rests against the glass, with the second electrode facing the internal volume of the case.
12 . The timepiece according to claim 10 , wherein the glass is formed by the substrate, and the second electrode faces the internal volume.
13 . The timepiece according to claim 10 , wherein the substrate forms a dial or is fixed against the dial or against a structure of the horological movement, and the second electrode faces the glass.