Patent Description:
The present disclosure relates to the technical field of photovoltaic cells, in particular to a structure of partial tunnel oxide passivated contact for a photovoltaic cell and a photovoltaic module.

Development of the solar photovoltaic market brings an increasingly urgent demand on a high-efficiency crystalline silicon cell. Continuous growth of the photovoltaic technology keeps reducing a manufacturing cost of the photovoltaic cells and renders market competition more fierce. Generally, a photovoltaic cell having high quality and a low cost is more competitive.

Surface passivation techniques for photovoltaic crystalline silicon is growing mature, and a degree of the passivation approaches its maximum. An open circuit voltage and conversion efficiency of the crystalline-silicon solar cell cannot be further improved mainly due to an excessive recombination current at a surface contact region between a metallic electrode and the crystalline silicon. Such current exceeds a recombination current at a non-metallic contact region by <NUM> orders of magnitude.

Tunnel oxide passivated contact is capable to suppress the recombination at the metallic contact region. In such structure, a silicon-based film has strong absorption on sunlight, which restricts application of the tunnel oxide passivated contact on a front surface of the crystalline silicon solar cells. Hence, the conversion efficiency of the crystalline silicon solar cells is hindered from further improvement.

<CIT> relates to a preparation method of a double-sided passivation contact P-type high-efficiency battery. The preparation method comprises the following steps: S1, cleaning and texturing; S2,preparing frontal polysilicon; S3, preparing a mask; S4, etching; S5, diffusion; S6, cleaning; S7, annealing; S8, preparing a back polysilicon layer; S9, preparing a front SiNx antireflection layer;and S10. The invention also discloses the double-sided passivation contact P-type high-efficiency battery comprising P-type monocrystalline silicon. An N-type emitter is provided with a front ultra-thin silicon oxide layer far from the P-type monocrystalline silicon. A back ultra-thin silicon oxide layer is arranged on the back surface of the P-type monocrystalline silicon. The contact structure is passivated by using the tunnel oxide layer on the front and back surfaces of the battery so as to have great surface passivation effect. The silicon surface is passivated exactly under the front metal gate line and the back aluminum back field so as to avoid direct contact between the metal and the silicon base, reduce the surface recombination and improve the conversion efficiency of the battery.

The article "<NPL>, discloses cells with both tunnel oxide passivated contacts and a tunnel passivation surface, but not on the same surface of the cell.

An objective of the present disclosure is to provide a structure of partial tunnel oxide passivated contact for a photovoltaic cell and a photovoltaic module. The contact structure and the photovoltaic module which are compatible with conventional mass production techniques of crystalline-silicon cells, thus can be put into mass production quickly, and can lead to fast improvement of efficiency and fast reduction of costs.

In order to address the above technical issues, a structure of partial tunnel oxide passivated contact for a photovoltaic cell is provided according to an embodiment of the present disclosure. The structure includes a cell body, a first tunnel oxide layer disposed on a surface of the cell body, and a first polysilicon film disposed on a surface of the tunnel oxide layer, where the surface of the cell body has a region for passivated contact and a region for light absorption, the first tunnel oxide layer is disposed in the region for passivated contact, and a projection of the first polysilicon film on the surface of the cell body is located in the region for passivated contact.

In an embodiment, the structure further includes a second tunnel oxide layer and a second polysilicon film that are disposed between the first tunnel oxide layer and the cell body layer, where both a projection of the second tunnel oxide layer and a projection of the second polysilicon film on the cell body cover the region for passivated contact and the region for light absorption.

In an embodiment, both a thickness of the first tunnel oxide layer and a thickness of the second tunnel oxide layer range from <NUM> to <NUM>.

In an embodiment, a thickness of the first polysilicon film ranges from <NUM> to <NUM>.

In an embodiment, a thickness of the second polysilicon film ranges from <NUM> to <NUM>.

In an embodiment, a thickness of the first tunnel oxide layer is equal to a thickness of the second tunnel oxide layer.

In an embodiment, the cell body is of a single-sided cell or a double-sided cell.

A photovoltaic module is further provided according to an embodiment of the present disclosure. The photovoltaic module includes a cell body and the forgoing structure that is disposed on the cell body.

The structure of partial tunnel oxide passivated contact for the photovoltaic cell and the photovoltaic module according to embodiments of the present disclosure have following advantages over conventional technology.

In the structure and the photovoltaic module according to embodiments of the present disclosure, the first tunnel oxide layer and the first polysilicon film merely cover the region for passivated contact, which improves a degree of passivation in such region, and suppress recombination at a surface of a cell. The first tunnel oxide layer and the first polysilicon film are not disposed in the region for light absorption, i.e., a region of non-metallic contact, which reduces blockage on sunlight and improves light absorption efficiency. The structure and the photovoltaic module are compatible with conventional mass production techniques of the crystalline-silicon cells, thus can be put into mass production quickly, and can lead to fast improvement of efficiency and fast reduction of costs.

For clearer illustration of the technical solutions according to embodiments of the present disclosure or conventional techniques, hereinafter are briefly described the drawings to be applied in embodiments of the present disclosure or conventional techniques. Apparently, the drawings in the following descriptions are only some embodiments of the present disclosure, and other drawings may be obtained by those skilled in the art based on the provided drawings without creative efforts.

Hereinafter technical solutions in embodiments of the present disclosure are described clearly and completely in conjunction with the drawings in embodiments of the present closure. Apparently, the described embodiments are only some rather than all of the embodiments of the present disclosure. Any other embodiments obtained based on the embodiments of the present disclosure by those skilled in the art without any creative effort fall within the scope of protection of the present disclosure.

Reference is made to <FIG> is a schematic diagram showing a structure of partial tunnel oxide passivated contact for a photovoltaic cell according to an embodiment of the present disclosure. <FIG> is a schematic diagram showing a structure of partial tunnel oxide passivated contact for a photovoltaic cell according to another embodiment of the present disclosure.

In a specific embodiment, a structure of partial tunnel oxide passivated contact for a photovoltaic cell includes a cell body <NUM>, a first tunnel oxide layer <NUM> disposed on a surface of the cell body <NUM>, and a first polysilicon film <NUM> disposed on a surface of the tunnel oxide layer. The surface of the cell body <NUM> includes a region for passivated contact and a region for light absorption. The first tunnel oxide layer <NUM> is disposed in the region for passivated contact, and a projection of the first polysilicon film <NUM> on the surface of the cell body <NUM> is located in the region for passivated contact.

The first tunnel oxide layer <NUM> and the first polysilicon film <NUM> merely cover the region for passivated contact, which improves a degree of passivation in such region, and suppress recombination at a surface of a cell. The first tunnel oxide layer <NUM> and the first polysilicon film <NUM> are not disposed in the region for light absorption, i.e., a region of non-metallic contact, which reduces blockage on sunlight and improves light absorption efficiency. The structure and the photovoltaic module are compatible with conventional mass production techniques of the crystalline-silicon cells, thus can be put into mass production quickly, and can lead to fast improvement of efficiency and fast reduction of costs.

In conventional technology, passivation contact cover the whole front side. In comparison, only a region of metallic contact is covered according to embodiments of the present disclosure, and thereby efficiency of a cell is improved.

A metallic electrode needs to be sintered on the surface of the first tunnel oxide layer <NUM> on a basis of the contact, and the first tunnel oxide layer <NUM> and the first polysilicon film <NUM> are quit thin. Hence, the first crystalline silicon thin film is apt to be burnt through during fabricating the metallic electrode, which might damage the cell body <NUM>. Such damages may be prevented to further suppress recombination at the metallic contact region and improve a performance of the cell. Hence, in an embodiment, the structure of partial tunnel oxide passivated contact for the photovoltaic cell further includes a second tunnel oxide layer <NUM> and a second polysilicon film <NUM>, which are disposed between the first tunnel oxide layer <NUM> and the cell body <NUM>. Both a projection of the second tunnel oxide layer <NUM> and a projection of the second polysilicon film <NUM> on the cell body <NUM> cover the region for passivated contact and the region for light absorption.

In the above structure, doping concentration of the first polysilicon film <NUM> is greater than that of the second polysilicon film <NUM>, which forms a "vertical conjunction" structure. The vertical conjunction in the passivated contact addresses incompatibility between complete passivation and light absorption, and incompatibility between the complete passivation and penetration damages due to the metallic electrode. Thereby, conversion efficiency of the cell is improved.

A thickness of the tunnel oxide layer and a manner of fabrication of the tunnel oxide layer are not limited herein. Generally, a thickness of the first tunnel oxide layer <NUM> and a thickness of the second tunnel oxide layer <NUM> both range from <NUM> to <NUM>.

A thickness of the silicon film of and a manner of depositing the silicon film are not limited herein. Generally, a thickness of the first polysilicon film <NUM> and a thickness of the second polysilicon film <NUM> both range from <NUM> to <NUM>.

Preferably, a thickness of the first tunnel oxide layer <NUM> is equal to a thickness of the second tunnel oxide layer <NUM>.

Preferably, a thickness of the first polysilicon film <NUM> is equal to a thickness of the second polysilicon film <NUM>.

In embodiments of the present disclosure, the cell body <NUM> may be a single-sided cell body <NUM> or a double-sided cell body <NUM>.

In one embodiment, a process of fabricating the foregoing structure of partial tunnel oxide passivated contact for the photovoltaic cell is as follows.

In another embodiment, a process of fabricating the foregoing structure of partial tunnel oxide passivated contact for the photovoltaic cell is as follows.

The above processes save a PECVD mask process when fabricating the structure of partial tunnel oxide passivated contact, and hence is simple. The above processes further save a laser etching process, and hence avoids damages on the silicon wafer substrate induced by a laser. The above processes can stop the etching on the polysilicon at the surface of the tunnel oxide layer, which protects the surface morphology of the silicon substrate and avoid re-texturing. The second foregoing process utilize the "vertical junction" structure in the passivated contact, which addresses incompatibility between complete passivation and light absorption and incompatibility between the complete passivation and penetration damages due to the metallic electrode. Thereby, conversion efficiency of the cell is improved. The second foregoing process save a PECVD mask process when fabricating the structure of partial tunnel oxide passivated contact, and hence is simple. The second foregoing process further save a laser etching process, and hence avoids damages induced by a laser on the ultra-thin passivated contact and the silicon wafer substrate. The second foregoing process can stop the etching on the polysilicon at the surface of the tunnel oxide layer, and can retain the ultra-thin passivated contact structure in the non-metallic contact region.

A photovoltaic module is further provided according to embodiments of the present disclosure. The photovoltaic module includes a cell body and the foregoing structure of partial tunnel oxide passivated contact for the photovoltaic cell, and the structure is disposed on the cell body.

The photovoltaic module including the forgoing structure has the same beneficial effects achieved by the forgoing structure. Hence, the beneficial effects are not repeated herein.

In view of the above, the structure of partial tunnel oxide passivated contact for the photovoltaic cell and the photovoltaic module are provided according to embodiments of the present disclosure. The first tunnel oxide layer and the first polysilicon film merely cover the region for passivated contact, which improves a degree of passivation in such region, and suppress recombination at a surface of a cell. The first tunnel oxide layer and the first polysilicon film are not disposed in the region for light absorption, i.e., a region of non-metallic contact, which reduces blockage on sunlight and improves light absorption efficiency. The structure and the photovoltaic module are compatible with conventional mass production techniques of the crystalline-silicon cells, thus can be put into mass production quickly, and can lead to fast improvement of efficiency and fast reduction of costs.

Claim 1:
A structure of partial tunnel oxide passivated contact for a photovoltaic cell, comprising:
a cell body (<NUM>);
a first tunnel oxide layer (<NUM>) on a surface of the cell body (<NUM>); and
a first polysilicon film (<NUM>) on a surface of the first tunnel oxide layer (<NUM>):
wherein the surface of the cell body (<NUM>) has a region for passivated contact and a region for light absorption, the first tunnel oxide layer (<NUM>) is disposed in the region for passivated contact, and a projection of the first polysilicon film (<NUM>) on the surface of the cell body (<NUM>) is located in the region for passivated contact;
characterized in that the structure further comprises:
a second tunnel oxide layer (<NUM>) on the surface of the cell body (<NUM>) and a second polysilicon film (<NUM>) on a surface of the second tunnel oxide layer (<NUM>), which are disposed between the first tunnel oxide layer (<NUM>) and the cell body (<NUM>), wherein:
both a projection of the second tunnel oxide layer (<NUM>) and a projection of the second polysilicon film (<NUM>) on the cell body (<NUM>) cover entirely the region for passivated contact and the region for light absorption.