WO2017068277A1

WO2017068277A1 - Photovoltaic cell with bypass diode

Info

Publication number: WO2017068277A1
Application number: PCT/FR2016/052691
Authority: WO
Inventors: Rémi Monna; Wilfried FAVRE; Eric Pilat
Original assignee: Commissariat à l'Energie Atomique et aux Energies Alternatives
Priority date: 2015-10-19
Filing date: 2016-10-18
Publication date: 2017-04-27
Also published as: FR3042644A1; FR3042644B1

Abstract

Photovoltaic cell with bypass diode. This photovoltaic cell includes a substrate (1) doped a first conductivity type, the substrate (1) comprising first and second opposite surfaces (10, 11), and four lateral surfaces (12); first and second semiconductor zones (100, 110) doped the first and a second conductivity type, respectively, and intended to make contact with an electrode (E); a bypass diode comprising a junction between the first and second semiconductor regions (2, 3), which are respectively doped the first and the second conductivity type; the photovoltaic cell being noteworthy in that the first and second semiconductor regions (2, 3) of the bypass diode make direct contact with the second and first semiconductor zones (110, 100), respectively; and in that the second semiconductor region (3) of the bypass diode makes direct contact with the four lateral surfaces (12) of the substrate (1).

Description

PHOTOVOLTAIC CELL WITH DERIVATION DIODE Technical field

The present invention relates to a photovoltaic cell, as well as to a method of manufacturing a photovoltaic cell. More specifically, the photovoltaic cell comprises a bypass diode (also called antiparallel diode, and "bypass diode" in English) to protect it in case of reverse bias. An inverse polarization of the photovoltaic cell can take place in the event of shading, and is likely to cause a strong reverse current that can locally damage the photovoltaic cell irreversibly (a phenomenon called "hot spot" in English).

State of the art

It is known from the state of the art to have parallel bypass diodes in a series of photovoltaic cells connected in series. Conventionally, there is a parallel branch diode for 9 cells connected in series. In case of shading of a photovoltaic cell among the whole, a strong loss of power is observed.

To overcome this problem, it is known from the state of the art, in particular US 2014/102531 (hereinafter D1), to monolithically integrate a bypass diode to each photovoltaic cell.

D1 discloses a photovoltaic cell, comprising:

a substrate of a doped semiconductor material of a first conductivity type, the substrate comprising first and second opposed surfaces, and four opposite two-to-two side surfaces connecting the first and second surfaces;

first and second semiconductor regions, respectively doped with the first and a second conductivity type, and respectively extending under the first and second surfaces of the substrate, each of the first and second semiconductor zones being intended to be in contact with an electrode;

a diode of derivation electrically isolated from the substrate, and comprising a junction between first and second semiconductor regions respectively doped with the first and the second type of conductivity, the first and second semiconductor regions of the bypass diode being respectively located at a distance from the first and second semiconductor zones.

In D1, the bypass diode is electrically isolated from the substrate via a trench.

Such a photovoltaic cell of D1 is not entirely satisfactory because the electrical contacts must be doubled. Indeed, it is necessary to provide electrical contacts for both the first and second semiconductor regions and for the first and second semiconductor regions of the bypass diode.

Presentation of the invention

Thus, the present invention aims to remedy all or part of the aforementioned drawbacks, and for this purpose concerns a photovoltaic cell, comprising:

a diode of derivation electrically isolated from the substrate, and comprising a junction between first and second respectively doped semiconductor regions of the first and the second type of conductivity, the first and second semiconductor regions of the bypass diode being respectively located remote from the first and second semiconductor regions;

the photovoltaic cell being remarkable in that the first and second semiconductor regions of the bypass diode are respectively in direct contact with the second and first semiconductor zones; and in that the second semiconductor region of the bypass diode is in direct contact with the four side surfaces of the substrate.

Thus, such a photovoltaic cell according to the invention makes it possible to dispense with electrical contacts dedicated to the photovoltaic cell and the diode of derivation because the first and second semiconductor regions of the bypass diode are respectively in direct contact with the second and first semiconductor regions. The bypass diode is a pn junction having a semiconductor region in direct contact with the four lateral surfaces of the substrate, which allows the passage of the reverse current via these lateral surfaces of the substrate in case of shading of the photovoltaic cell. The first region of the bypass diode is located at a distance (i.e., without direct contact) from the first semiconductor region. The second region of the bypass diode is located at a distance (i.e., without direct contact) from the second semiconductor zone.

Advantageously, the photovoltaic cell comprises an insulating zone, made of a compensated semiconductor material, arranged to electrically isolate the bypass diode and the substrate.

Preferably, the compensated semiconductor material is obtained from the second semiconductor zone.

Thus, it is possible to easily form the insulating zone from the second semiconductor zone. Advantageously, the insulating zone extends between the second semiconductor region of the bypass diode and the second semiconductor zone.

Advantageously, the insulating zone extends under the second surface of the substrate.

Advantageously, the insulating zone extends at the periphery of the second surface of the substrate.

Thus, such an insulating zone is disposed in the vicinity of the second semiconductor region of the bypass diode, thereby facilitating electrical isolation between the second semiconductor region and the second semiconductor region.

Advantageously, the first semiconductor region of the bypass diode extends over the insulating zone. Advantageously, the insulating zone has a free carrier concentration of less than 10 ¹⁴ at.cm- ³ .

Thus, it is possible to form the insulating zone from the compensated semiconductor material of the second semiconductor zone.

According to one embodiment, each of the first or second semiconductor regions of the bypass diode comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

- boron or aluminum atoms when their conductivity type is the type P-

According to one embodiment, each of the first or second semiconductor zones comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

- boron or aluminum atoms when their conductivity type is the type P-

Advantageously, the semiconductor material of the substrate is based on crystalline silicon.

The present invention also relates to a method of manufacturing a photovoltaic cell according to the invention, comprising the steps:

predictable :

first and second semiconductor regions, respectively doped with the first and a second type of conductivity, and extending respectively under the first and second surfaces of the substrate, each of the first and second second semiconductor regions being intended to be in contact with an electrode;

b) forming a bypass diode electrically isolated from the substrate, and comprising a junction between first and second semiconductor regions respectively doped with the first and the second conductivity type, the first and second semiconductor regions of the bypass diode being respectively located at a distance from the first and second semiconductor zones;

the method being remarkable in that step b) is performed so that the first and second semiconductor regions of the bypass diode are respectively in direct contact with the second and first semiconductor regions, and so that the second semiconductor region of the bypass diode is in direct contact with the side surfaces of the substrate. Thus, such a method according to the invention makes it possible to dispense with electrical contacts dedicated to the photovoltaic cell and to the bypass diode because the first and second semiconductor regions of the bypass diode are respectively in direct contact with the second and first semiconductor regions. The bypass diode is a p-n junction having a semiconductor region in direct contact with the four lateral surfaces of the substrate, which allows the passage of the reverse current via these lateral surfaces of the substrate in case of shading of the photovoltaic cell.

Advantageously, step a) comprises the steps:

a1) providing the substrate of the doped semiconductor material of the first conductivity type, the substrate comprising the first and second opposing surfaces, and the four opposite side surfaces in pairs connecting the first and second surfaces;

a2) forming a dielectric layer at the second surface and the side surfaces, the dielectric layer having dopants of the second conductivity type;

a3) diffusing the dopants of the second conductivity type from the dielectric layer to the second surface and up to the four side surfaces of so as to form respectively the second semiconductor region and the second semiconductor region of the bypass diode.

Thus, steps a2) and a3) make it possible to concomitantly form the second semiconductor zone and the second semiconductor region of the bypass diode so as to limit the operation time of the method.

Advantageously, step a) comprises a step a4) of incorporating the dopants of the first type of conductivity, preferably in the gas phase, to the first surface of the substrate so as to form the first semiconductor zone.

Advantageously, step b) comprises a step b1) of removing at least a portion of the dielectric layer formed in step a2). According to one embodiment, step b1) is executed so as to expose a portion, preferably peripheral, of the second surface of the substrate; and step b) comprises a step b2) of incorporating the dopants of the first conductivity type, preferably in the gas phase, to the portion of the second surface of the substrate exposed after step b1); steps b2) and a4) being preferably concomitant.

Advantageously, step b2) is executed so as to form:

an insulating zone extending between the second semiconductor region of the bypass diode and the second semiconductor zone;

the first semiconductor region of the bypass diode extending over the insulating zone.

According to an implementation variant, step b1) is executed so as to completely eliminate the dielectric layer formed during step a2); and step b) comprises a step b2 ') consisting of:

applying a solution comprising the dopants of the first type of conductivity to a portion, preferably peripheral, of the second surface of the substrate;

irradiating the part of the second surface of the substrate with a laser. The application of the solution and the irradiation during step b2 ') are advantageously concomitant. To do this, the solution is advantageously incorporated into the laser beam. Advantageously, step b2 ') is executed so as to form:

Brief description of the drawings

Other characteristics and advantages will appear in the following description of various embodiments of the invention, given by way of non-limiting examples, with reference to the appended drawings in which:

FIG. 1 is a schematic perspective view of a photovoltaic cell according to the invention,

FIG. 2 is a partial schematic perspective view of a photovoltaic cell according to the invention,

FIG. 3 is a schematic sectional view of a photovoltaic cell according to the invention, along the sectional plane P of FIG. 1,

- Figure 4 is a graph showing in abscissa the implantation depth (in nm) and the ordinate the dopant concentration (at cm. ^"3), according to various fluences of a laser (in J. ^{cm" 2,} which a reference denoted REF),

FIGS. 5a to 5g are schematic sectional views illustrating steps of a first method of manufacturing a photovoltaic cell according to the invention,

- Figures 6a to 6f are schematic sectional views illustrating steps of a second method of manufacturing a photovoltaic cell according to the invention.

Detailed description of the embodiments

For the different embodiments, the same references will be used for identical elements or ensuring the same function, for the sake of simplification of the description. The technical characteristics described below for different embodiments are to be considered in isolation or in any technically possible combination. A photovoltaic cell according to the invention comprises:

a substrate 1 of a doped semiconductor material of a first conductivity type, the substrate 1 comprising opposite first and second surfaces 10, 11, and four opposite side surfaces 12 connecting the first and second surfaces 10, 1 1;

first and second semiconductor regions 100, 1 10, respectively doped with the first and a second type of conductivity, and extending respectively under the first and second surfaces 10, 11 of the substrate 1, each of the first and second second semiconductor regions 100, 1 being intended to be in contact with an electrode E;

a diode of derivation electrically isolated from the substrate 1, and comprising a junction between first and second semiconductor regions 2, 3 respectively doped with the first and the second type of conductivity, the first and second semiconductor regions 2, 3 of the bypass diode being respectively located at a distance from the first and second semiconductor regions 100, 1 10.

The first and second semiconductor regions 2, 3 of the bypass diode are respectively in direct contact with the second and first semiconductor regions 1 10, 100. The second semiconductor region 3 of the bypass diode is in contact direct with the four lateral surfaces 12 of the substrate 1.

The semiconductor material of the substrate 1 is advantageously based on crystalline silicon. The substrate 1 advantageously has a resistivity of between 1 and 10 Ω.cm. The four lateral surfaces 12 of the substrate 1 extend in a direction parallel to normal to the substrate 1. The four lateral surfaces 12 of the substrate 1 have a ring-shaped cross section. "Transverse" means a direction perpendicular to the normal to the substrate 1. Each side surface 12 forms a physical edge of the substrate 1.

The first type of conductivity is type n or type p. The second type of conductivity is type n or type p. When the first type of conductivity is n type, then the second type of conductivity is the type p. When the first type of conductivity is the type p, then the second type of conductivity is the type n. In other words, the first and second types of conductivity are opposite. Preferably, the first and second semiconductor zones 100, 1 10 are spaced from the lateral surfaces 12 of the substrate 1 by a distance of the order of 0.2 to 1 μιτι in the transverse direction.

The first semiconductor region 100 has a dopant concentration of the first conductivity type, preferably between 10 ¹⁸ and 10 ²⁰ at.cm ^"3. The second semiconductor zone 1 10 has a doping concentration C2 of the second type conductivity. C2 is preferably between 10 ¹⁸ and 10 ²⁰ at.cm ^"3.

Each of the first or second semiconductor zones 100, 1 10 advantageously comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

- The boron or aluminum atoms when their conductivity type is the type P- The photovoltaic cell advantageously comprises an insulating zone 4, made of a compensated semiconductor material, arranged to electrically isolate the bypass diode and the substrate 1 . The insulating zone 4 advantageously extends between the second semiconductor region 3 of the bypass diode and the second semiconductor zone 1 10. The insulating zone 4 advantageously extends under the second surface 1 1 of the substrate 1. The insulating zone 4 advantageously extends around the periphery of the second surface 1 1 of the substrate 1.

The compensated semiconductor material of the insulating zone 4 is the semiconductor material of the substrate 1. The insulating zone 4 advantageously has a concentration of free carriers less than 10 ¹⁴ at.cm- ³ The insulating zone 4 advantageously has a resistivity greater than 500 Ω.cm.The insulating zone 4 preferably has a thickness of between 0.1 and 0.5 μιτι "Thickness" means the dimension following the normal to the substrate 1. The first semiconductor region 2 of the bypass diode advantageously extends over the insulating zone 4. The second semiconductor region 3 of the bypass diode preferably extends all along the lateral surfaces 12 of the substrate 1. The second semiconductor region 3 preferably extends within the substrate 1, in direct contact with the lateral surfaces 12. The bypass diode is thus integrated under each electrode E, at the periphery of the photovoltaic cell, which makes it possible to not use the active surface of the photovoltaic cell, and thereby avoid a loss of efficiency for the photovoltaic cell.

Each of the first or second semiconductor regions 2, 3 of the bypass diode advantageously comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

boron or aluminum atoms when their conductivity type is the p type.

Each of the first or second semiconductor regions 2, 3 of the bypass diode advantageously has:

- a dopant concentration of between 5.10 ¹⁹ and 3.10 ²⁰ at.cm ^"3 when their conductivity type is n-type;

a dopant concentration of between 5.10 ¹⁸ and 5.10 ¹⁹ at.cm- ³ when their conductivity type is the p type.

The junction between the first and second semiconductor regions 2, 3 preferably has a thickness of between 0.3 and 0.5 μιτι. The photovoltaic cell advantageously comprises a first dielectric layer 5 arranged to cover the bypass diode. The first dielectric layer 5 is preferably a silicon oxide. The first dielectric layer preferably has a thickness of between 2 and 10 nm. The photovoltaic cell advantageously comprises a second dielectric layer 6 covering the first dielectric layer 5. The second dielectric layer 6 is preferably a silicon nitride. The second dielectric layer preferably has a thickness of between 20 and 100 nm. Each electrode E is advantageously made of silver and / or aluminum. The electrode E in contact with the second semiconductor zone 1 10 is also in contact with the first semiconductor region 2 of the bypass diode. The electrode E in contact with the first semiconductor zone 100 is also in contact with the second semiconductor region 3 of the bypass diode.

A first method of manufacturing a photovoltaic cell according to the invention, illustrated in FIGS. 5a to 5g, comprises the steps:

predictable :

b) forming an electrically isolated bypass diode of the substrate 1, and comprising a junction between first and second semiconductor regions 2, 3 respectively doped with the first and the second type of conductivity, the first and second semiconductor regions 2, 3 of the bypass diode being respectively located at a distance from the first and second semiconductor zones 100, 1 10.

Step b) is executed so that the first and second semiconductor regions 2, 3 of the bypass diode are respectively in direct contact with the second and first semiconductor regions 1 10, 100, and so that the second semiconductor region 3 of the bypass diode is in direct contact with the four side surfaces 12 of the substrate 1.

Advantageously, step a) comprises the steps: a1) providing the substrate 1 of the doped semiconductor material of the first conductivity type, the substrate 1 comprising the first and second surfaces 10, 1 1 opposite, and the four side surfaces 12 opposite in pairs connecting the first and second surfaces 10 , 1 1;

a2) forming a dielectric layer 8 at the second surface 11 and the side surfaces 12, the dielectric layer 8 having dopants of the second conductivity type; the steps a1) and a2) being illustrated in FIG. 5a,

a3) diffusing the dopants of the second conductivity type from the dielectric layer 8 to the second surface 11 and up to the four lateral surfaces 12 so as to form the second semiconductor zone 1 10 and the second semiconductor region respectively conductor 3 of the bypass diode, step a3) being illustrated in Figure 5b.

The dielectric layer 8 formed during step a2) is preferably a doped SiO _x silicon oxide. The first surface 10 of the substrate 1 is devoid of the dielectric layer 8 formed during step a2).

Step a2) is advantageously carried out by a chemical vapor deposition of the dielectric layer 8. When the dielectric layer 8 is a silicon oxide, the chemical vapor deposition is carried out using reactive gases comprising SiH ₄ silane and N ₂ O nitrous oxide. When the dielectric layer 8 comprises phosphorus or arsenic atoms, forming n-type dopants, said atoms are advantageously incorporated into the silicon oxide by an injection of phosphine PH ₃ or arsine AsH ₃ with the reactive gases. When the dielectric layer 8 comprises boron atoms, forming p-type dopants, said atoms are advantageously incorporated into the silicon oxide by an injection of diborane B ₂ H ₆ with the reactive gases.

Step a3) is advantageously carried out by thermal annealing applied to the assembly formed by the substrate 1 and the dielectric layer 8, preferably in a furnace. The thermal annealing applied during step a3) advantageously has:

an annealing temperature value of between 850 ° C. and 940 ° C.,

- a value of annealing time of between 10 minutes and 1 hour.

For example, when the dielectric layer 8 is a silicon oxide

SiOx, x is of the order of 0.768 before thermal annealing, and is of the order of 1. 828 after thermal annealing. As illustrated in FIG. 5c, step b) advantageously comprises a step b1) of eliminating at least a portion of the dielectric layer 8 formed during step a2). Step b1) is performed so as to expose a part, preferably peripheral, of the second surface 1 1 of the substrate 1. Step b1) is preferably performed by laser ablation. For example, the laser is a pulsed laser with a pulse duration of the order of 15 ps; the wavelength of the laser is 355 nm or 532 nm with a frequency of between 50 kHz and 200 kHz; the fluence of the laser is between 0.1 and 1 J.cm ^-2 .

As illustrated in FIG. 5d, step b) advantageously comprises a step b2) of incorporating the dopants of the first type of conductivity, preferably in the gas phase, to the portion of the second surface 11 of the substrate exposed after step b1). Step b2) is advantageously carried out by thermal annealing applied to the assembly formed by the substrate 1 and the dielectric layer 8, preferably in a furnace. The thermal annealing applied during step b2) advantageously has:

an annealing temperature value of between 850 ° C. and 940 ° C.,

- a value of annealing time of between 10 minutes and 1 hour.

When the dopants of the first conductivity type are phosphorus atoms, thermal annealing is advantageously applied during step b2) under an atmosphere containing dioxygen and POCI3. When the dopants of the first conductivity type are boron atoms, the thermal annealing is advantageously applied during step b2) under an atmosphere containing oxygen, and BBr ₃ or BCI3.

Step b2) is advantageously executed so as to form:

an insulating zone 4 extending between the second semiconductor region 3 of the bypass diode and the second semiconductor zone 1 10;

the first semiconductor region 2 of the bypass diode extending over the insulating zone 4.

As illustrated in FIG. 5d, step a) advantageously comprises a step a4) of incorporating the dopants of the first type of conductivity, preferably in the gas phase, to the first surface 10 of the substrate 1 of in order to form the first semiconductor zone 100. The steps b2) and a4) are preferably concomitant.

As illustrated in FIG. 5e, the first method advantageously comprises a step c) of removing the dielectric layer 8, preferably by chemical etching, for example by means of hydrofluoric acid, for a period of 5 to 20 minutes.

As illustrated in FIG. 5f, the first method advantageously comprises the steps:

d) forming a first dielectric layer 5 arranged to cover the bypass diode and the first and second semiconductor regions 100, 1 10;

e) forming a second dielectric layer 6 covering the first dielectric layer.

The first dielectric layer 5 is preferably a silicon oxide. The first dielectric layer 5 preferably has a thickness of between 2 and 10 nm. The second dielectric layer 6 is preferably a silicon nitride. The second dielectric layer 6 preferably has a thickness of between 20 and 100 nm.

As illustrated in FIG. 5g, the first method advantageously comprises a step f) of bringing each of the first and second semiconductor regions 100, 1 10 and each of the first and second semiconductor regions 2, 3 of the diode into contact with each other. Preferably, step f) comprises a metallization step, preferably performed by screen printing, followed by an annealing step preferably carried out at a temperature of between 720 ° C. and 850 ° C. for 5 to 15 minutes. seconds in an oven with infrared lamps with air passage. Thus, the metal can pass through the first and second dielectric layers 5, 6 formed during steps d) and e). Each electrode E is advantageously made of silver and / or aluminum.

A second method of manufacturing a photovoltaic cell according to the invention, illustrated in FIGS. 6a to 6f, comprises the steps: predictable :

first and second semiconductor regions 100, 1 10, respectively doped with the first and second conductivity type, and extending respectively under the first and second surfaces 10, 1 1, each of the first and second semi zones; -conductrices 100, 1 10 being intended to be in contact with an electrode E;

Advantageously, step a) comprises the steps:

a1) providing the substrate 1 of the doped semiconductor material of the first conductivity type, the substrate 1 comprising the first and second surfaces 10, 1 1 opposite, and the four side surfaces 12 opposite in pairs connecting the first and second surfaces 10 , 1 1;

a2) forming a dielectric layer 8 at the second surface 11 and the side surfaces 12, the dielectric layer 8 having dopants of the second conductivity type; the steps a1) and a2) being illustrated in FIG. 6a,

a3) diffusing the dopants of the second conductivity type from the dielectric layer 8 to the second surface 11 and up to the four lateral surfaces 12 so as to form the second semiconductor zone 1 10 and the second semiconductor region 3 of the bypass diode, step a3) being illustrated in FIG. 6b.

Step a2) is advantageously carried out by a chemical vapor deposition of the dielectric layer 8. When the dielectric layer 8 is a silicon oxide, the chemical vapor deposition is carried out using reactive gases comprising SiH ₄ silane and N ₂ O nitrous oxide. When the dielectric layer 8 comprises phosphorus or arsenic atoms, forming n-type dopants, said atoms are advantageously incorporated into the silicon oxide by an injection of phosphine PH ₃ or arsine AsH ₃ with the reactive gas. When the dielectric layer 8 comprises boron atoms, forming p-type dopants, said atoms are advantageously incorporated into the silicon oxide by an injection of diborane B ₂ H ₆ with the reactive gases.

an annealing temperature value of between 850 ° C. and 940 ° C.,

- a value of annealing time of between 10 minutes and 1 hour.

By way of example, when the dielectric layer 8 is a SiOx silicon oxide, x is of the order of 0.768 before thermal annealing, and is of the order of 1.828 after thermal annealing.

As illustrated in FIG. 6b, step a) advantageously comprises a step a4) of incorporating the dopants of the first type of conductivity, preferably in the gas phase, to the first surface 10 of the substrate 1 so as to form the first semiconductor zone 100. When the dopants of the first conductivity type comprise phosphorus atoms forming n-type dopants, a phosphor glass 9, P2O ₅ -S1O2, is also formed at the first surface 10 of the substrate 1 when of step a4). As illustrated in FIG. 6c, step b) advantageously comprises a step b1) of completely eliminating the dielectric layer 8 formed during step a2), as well as the phosphor glass 9.

As illustrated in FIG. 6d, step b) advantageously comprises a step b2 ') consisting of:

applying a solution comprising the dopants of the first type of conductivity to a portion, preferably a peripheral portion, of the second surface 11 of the substrate 1;

irradiating the part of the second surface 1 1 of the substrate 1 with a laser 7.

Step b2 ') is advantageously executed so as to form:

For this purpose, the laser 7 used in step b2 ') is a pulsed laser with a pulse duration of between 10 and 150 ns; the wavelength of the laser 7 is 515 nm or 532 nm with a frequency between 10 kHz and 300 kHz; the fluence of the laser is between 0.8 and 1.8 J.cm ^-2 .The depth of the doping is adapted by modifying the fluence of the laser 7, as illustrated in FIG.

As illustrated in FIG. 6e, the second method advantageously comprises the steps:

c) forming a first dielectric layer 5 arranged to cover the bypass diode and the first and second semiconductor regions 100, 1 10;

d) forming a second dielectric layer 6 covering the first dielectric layer.

The first dielectric layer 5 is preferably a silicon oxide. The first dielectric layer 5 preferably has a thickness of between 2 and 10 nm. The second dielectric layer 6 is preferably a silicon nitride. The second dielectric layer 6 preferably has a thickness of between 20 and 100 nm. As illustrated in FIG. 6f, the second method advantageously comprises a step e) of bringing each of the first and second semiconductor regions 100, 1 10 and each of the first and second semiconductor regions 2, 3 of the diode into contact with each other. by way of an electrode E. Step e) advantageously comprises a metallization step, preferably carried out by screen printing, followed by an annealing step preferably carried out at a temperature of between 720 ° C. and 850 ° C. for 5 to 15 minutes. seconds in an oven with infrared lamps with air passage. Thus, the metal can pass through the first and second dielectric layers 5, 6 formed in steps c) and d). Each electrode E is advantageously made of silver and / or aluminum.

Claims

claims

1. Photovoltaic cell, comprising:

a substrate (1) of doped semiconductor material of a first conductivity type, the substrate (1) comprising first and second surfaces (10,

1 1) and four opposing lateral surfaces (12) in pairs connecting the first and second surfaces (10, 1 1);

first and second semiconductor regions (100, 1 10) respectively doped with the first and a second conductivity type, and respectively extending under the first and second surfaces (10, 1 1) of the substrate (1 ), each of the first and second semiconductor regions (100, 1 10) being intended to be in contact with an electrode (E);

a diode of derivation electrically isolated from the substrate (1), and comprising a junction between first and second semiconductor regions (2, 3) respectively doped with the first and the second type of conductivity, the first and second semiconductor regions; (2, 3) of the bypass diode being respectively located at a distance from the first and second semiconductor regions (100, 1 10);

the photovoltaic cell being characterized in that the first and second semiconductor regions (2, 3) of the bypass diode are respectively in direct contact with the second and first semiconductor regions (1 10, 100); and in that the second semiconductor region (3) of the bypass diode is in direct contact with the four side surfaces (12) of the substrate (1).

2. Photovoltaic cell according to claim 1, characterized in that it comprises an insulating zone (4), made of a compensated semiconductor material, arranged to electrically isolate the bypass diode and the substrate (1).

Photovoltaic cell according to claim 2, characterized in that the insulating zone (4) extends between the second semiconductor region (3) of the bypass diode and the second semiconductor zone (1 10).

4. Photovoltaic cell according to claim 2 or 3, characterized in that the insulating zone (4) extends under the second surface (1 1) of the substrate (1).

5. Photovoltaic cell according to one of claims 2 to 4, characterized in that the insulating zone (4) extends at the periphery of the second surface (1 1) of the substrate (1).

6. Photovoltaic cell according to one of claims 2 to 5, characterized in that the first semiconductor region (2) of the bypass diode extends over the insulating region (4).

7. Photovoltaic cell according to one of claims 2 to 6, characterized in that the insulating zone (4) has a concentration of free carriers less than 10 ¹⁴ at.cm- ³ .

Photovoltaic cell according to one of claims 1 to 7, characterized in that each of the first or second semiconductor regions (2, 3) of the bypass diode comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

- boron or aluminum atoms when their conductivity type is the type P-

9. Photovoltaic cell according to one of claims 1 to 8, characterized in that each of the first or second semiconductor zones (100, 1 10) comprises:

phosphorus or arsenic atoms when their conductivity type is n-type;

boron or aluminum atoms when their conductivity type is the p type.

10. Photovoltaic cell according to one of claims 1 to 9, characterized in that the semiconductor material of the substrate (1) is based on crystalline silicon.

1 1. A method of manufacturing a photovoltaic cell according to one of claims 1 to 10, comprising the steps:

predictable :

a substrate (1) of a doped semiconductor material of a first conductivity type, the substrate (1) comprising opposite first and second surfaces (10, 1 1), and four opposite lateral surfaces (12). two connecting the first and second surfaces (10, 1 1);

b) forming an electrically isolated bypass diode of the substrate (1), and comprising a junction between first and second semiconductor regions (2, 3) respectively doped with the first and second conductivity type, the first and second semi regions -conductors (2, 3) of the bypass diode being respectively located at a distance from the first and second semiconductor regions (100, 1 10);

the method being characterized in that step b) is performed so that the first and second semiconductor regions (2, 3) of the bypass diode are respectively in direct contact with the second and first semiconductor regions ( 1 10, 100), and so that the second semiconductor region (3) of the bypass diode is in direct contact with the four side surfaces (12) of the substrate (1).

12. Method according to claim 1 1, characterized in that step a) comprises the steps:

a1) providing the substrate (1) of the doped semiconductor material of the first conductivity type, the substrate (1) comprising the first and second opposed surfaces (10, 1 1), and the four opposite side surfaces (12) two connecting the first and second surfaces (10, 1 1); a2) forming a dielectric layer (8) at the second surface (11) and the four side surfaces (12), the dielectric layer (8) having dopants of the second conductivity type;

a3) diffusing the dopants of the second conductivity type from the dielectric layer (8) to the second surface (1 1) and to the four lateral surfaces (12) so as to form the second semiconductor region (1 10) and the second semiconductor region (3) of the bypass diode.

13. The method of claim 12, characterized in that step a) comprises a step a4) of incorporating the dopants of the first conductivity type, preferably in the gas phase, to the first surface (10) of the substrate. (1) to form the first semiconductor region (100).

14. The method of claim 12 or 13, characterized in that step b) comprises a step b1) of removing at least a portion of the dielectric layer (8) formed in step a2).

15. The method of claim 14, characterized in that step b1) is performed so as to expose a portion, preferably peripheral, of the second surface (1 1) of the substrate (1); and in that step b) comprises a step b2) of incorporating the dopants of the first conductivity type, preferably in the gas phase, to the portion of the second surface (1 1) of the exposed substrate (1) after step b1); steps b2) and a4) being preferably concomitant when claim 14 depends on claim 13.

16. The method of claim 15, characterized in that step b2) is executed so as to form:

an insulating zone (4) extending between the second semiconductor region (3) of the bypass diode and the second semiconductor zone (1 10);

the first semiconductor region (2) of the bypass diode extending over the insulating zone (4).

17. The method of claim 14, characterized in that step b1) is performed so as to completely eliminate the dielectric layer (8) formed in step a2); and in that step b) comprises a step b2 ') consisting of:

applying a solution comprising the dopants of the first type of conductivity to a part, preferably a peripheral part, of the second surface (1 1) of the substrate

(1);

- irradiating the portion of the second surface (1 1) of the substrate (1) with a laser (7).

18. The method of claim 17, characterized in that step b2 ') is executed so as to form: