Method for improving ohmic contact properties between contact grid and emitter layer of a silicon solar cell

Abstract

This invention relates to a method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell, wherein in a processing step, a current density of 200 A / cm² is generated locally by induction while applying a preset voltage to and irradiating the silicon solar cell. 2 Up to 20000A / cm 2 The processing current. The object of the present invention is to improve the method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell. In particular, the improvement achieved by the method should be quantified when implementing the method. Furthermore, possible damage caused by using unfavorable method parameters should be identified when implementing the method. The solution of the present invention to achieve the above object is to perform a measurement step before and / or after the processing step, in which a current intensity of 1 mA / cm is generated by induction by irradiating the sun-facing side of the silicon solar cell and applying a preset voltage. 2 Up to 500mA / cm 2 The measurement current, and the current intensity of the measurement current detected by an ammeter, and stored in correspondence with the corresponding measurement location.

Description

[0001] This invention relates to a method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell. In one processing step, a voltage less than the breakdown voltage of the silicon solar cell, reversed from the forward direction of the silicon solar cell, is applied between the contact grid and the back contact using a voltage source and a contact device connected to the voltage source. While the voltage is applied, a point light source is guided within a region on the sun-facing side of the silicon solar cell. During this process, a processed area of ​​the sun-facing side is irradiated, thereby generating a processing current within the corresponding area through induction. The processing current has a value of 200 A / cm² for the processed area. 2 Up to 20000 A / cm 2 The current density is applied to the partition for a period of 10 ns to 10 ms.

[0002] In the manufacturing process of crystalline silicon solar cells, metal paste is applied to the front end of a contact grid coated with dielectric silicon nitride using screen printing. For the contact of the emitter layer beneath the silicon nitride layer in the silicon solar cell, a tempering step is performed at 800-900°C after applying the metal paste. During this process, with the assistance of glass powder contained in the metal paste, the silver in the metal paste diffuses through the silicon nitride layer into the emitter layer. Process control during the tempering step has a decisive influence on contact formation. With proper process control, the transition between the contact grid and the emitter layer is characterized by low contact resistance. With defective process control, only a higher contact resistance is typically achieved. If, for example, too low a temperature is applied during the tempering step, the metal paste cannot diffuse sufficiently through the silicon nitride layer, resulting in only a small contact area and high contact resistance between the contact grid and the emitter layer. High contact resistance leads to a significant reduction in the efficiency of the solar cell, making it unsuitable for use in solar modules and thus rendering it unusable.

[0003] In the prior art, a method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell is known from DE 10 2018 001 057 A1. In this method, a preset voltage is applied to the silicon solar cell in the reverse direction of the forward direction, and scanning is performed using a point light source. During this process, a current density of 200 A / cm² is generated within the corresponding illuminated section of the solar cell. 2 Up to 20000 A / cm 2The processing current is on the order of magnitude. A point light source is directed onto this solar cell, causing the processing current to act on this region for 10 ns to 10 ms. This current, generated by the interaction of illumination and a voltage reversed to the forward direction of the silicon solar cell, improves the ohmic contact characteristics between the contact grid and the emitter layer of the silicon solar cell.

[0004] However, a drawback is that to quantify the improvement in ohmic contact characteristics achieved through this method, the solar cell must be electrically characterized after applying the method. This characterization could, for example, involve recording the IU characteristic curve of the solar cell under illumination in a solar simulator, where the improvement in contact characteristics can be derived from the series resistance of the silicon solar cell determined by the IU characteristic curve. However, the measurement of the solar cell before and after applying the known method makes the overall processing of the solar cell quite difficult. Furthermore, applying this method to improve the ohmic contact characteristics in individual solar cells may also cause damage, because, for example, parameters (e.g., shorter current duration) need to be set in each section of these solar cells, different from the rest of the solar cells. The ohmic contact characteristics between the contact grid and the emitter layer of the silicon solar cell can also change locally, which in principle requires corresponding parameter changes when applying the known method. Such local parameter changes can be adjusted using known methods. However, when applying the known method, the areas of the silicon solar cell that require corresponding local parameter changes are unknown.

[0005] The object of this invention is to improve a method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell. In particular, the improvement achieved by the method should be quantified during its implementation. Furthermore, potential damage caused by using unfavorable method parameters should be identified during the implementation of the method.

[0006] The solution of the present invention to achieve the above-mentioned objective is a method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell.

[0007] In the known method section, a silicon solar cell comprising an emitter layer, a contact grid, and a back contact is first provided. In one processing step, a voltage less than the breakdown voltage of the silicon solar cell, reversed from the forward direction, is applied between the contact grid and the back contact by means of a contact device and a voltage source. When this voltage is applied, a point light source is directed within a region on the sun-facing side of the silicon solar cell, illuminating a processing area of ​​the sun-facing section, thereby inducing a processing current within the corresponding section, and this processing current having a value of 200 A / cm for the processing area. 2 Up to 20000 A / cm 2The current density is applied to the partition for a period of 10 ns to 10 ms.

[0008] According to the invention, a measurement step is performed before and / or after the processing step. In this measurement step, a voltage is applied between the contact grid and the back contact using a voltage source and a contact device. In this case, when this voltage is applied, a measurement section of the sun-facing side of the silicon solar cell is illuminated with a point light source, wherein the voltage and illumination intensity are set such that a measurement current is induced within the corresponding section, the measurement current having a value of 1 mA / cm for the measurement section. 2 Up to 500 mA / cm 2 The current density is measured using an ammeter at a given voltage and irradiation intensity, and the result is stored corresponding to the measured locality.

[0009] In this scenario, the current intensity measured at the corresponding measurement location can be used for subsequent processing, such as process monitoring, process control, or quality control. Regions with good ohmic contact characteristics or small local short-circuit currents between the contact grid and the emitter layer are exposed due to higher current intensity compared to regions with poor ohmic contact characteristics. Since the current intensity is stored corresponding to the corresponding measurement location and / or processing location, spatially resolved information about the electrical characteristics of the silicon solar cell exists. In this case, this spatially resolved information is used as a regulating variable for the processing steps. During the processing steps, to influence the processing current, the irradiation intensity of the point light source and / or the duration of irradiation and / or the level of the voltage reversed to the forward direction of the silicon solar cell can be adjusted during irradiation.

[0010] Depending on the specific measurement information desired, the voltage applied in the measurement step is opposite to the forward direction of the silicon solar cell and less than the breakdown voltage of the silicon solar cell, or the voltage applied in the measurement step is oriented along the forward direction of the silicon solar cell.

[0011] In another embodiment of the method of the invention, during the processing step, a corresponding processing current is also detected with an ammeter for at least a portion of the irradiated processing area, and stored corresponding to the corresponding processing area. The detection of the intensity of the measurement current and the detection of the intensity of the processing current can be performed selectively. For example, the measurement step can be performed only before the processing step, without simultaneously detecting the processing current during the processing step, and without performing another measurement step after the processing step. Similarly, for example, the processing current can be detected only during the processing step, without performing any measurement steps upstream or downstream of the processing step. Likewise, the measurement step can be performed before or after the processing step, and the processing current can be detected simultaneously during the processing step, or the measurement current can be detected only in a measurement step upstream or downstream of the processing step, without detecting the processing current during the processing step.

[0012] In this case, the detected and stored processing current value can be used for subsequent processing, such as process monitoring, process control, or quality control.

[0013] In the method of the present invention, during the measurement step, the intensity of the measuring current is detected under a given voltage and a given irradiation intensity. It is well known that electrical measurements can also be performed when the current is constant and the corresponding voltage is detected. Thus, the measurement step of the method of the present invention can be implemented such that a constant current is preset and the corresponding voltage is detected using a voltmeter, and the data is stored corresponding to the corresponding measurement or processing section. That is, these two forms of measurement are considered equivalent within the scope of the present invention.

[0014] The method of the present invention is not limited to storing the current intensity corresponding to the corresponding measurement or processing area of ​​the measured or processed current. Storage can also be implemented in a converted form, for example, as current density, where the corresponding current intensity is calculated, for example, by the area of ​​the measurement area. Alternatively, the current intensity can be stored as a resistance value, for example, in relation to the applied voltage.

[0015] The voltage source and contact device used in the measurement step can be the same as those used in the processing step. This has the advantage of eliminating the need for additional contact devices. However, the invention is not limited to this. In principle, another contact device and / or another voltage source can also be used as the contact device and / or voltage source for detecting the processing current. Of course, it is equally advantageous to use the same point light source in both the processing and measurement steps, but the invention is not limited to this, and different point light sources can also be used in principle.

[0016] By detecting the processing current and / or measuring the current, the detected current can be used as a measure of the quality of the ohmic contact characteristics between the contact grid and the emitter layer. Under continuous irradiation and applied voltage, sections with good ohmic contact characteristics between the contact grid and the emitter layer exhibit a larger measured current than sections with poor ohmic contact characteristics. Sections with poor ohmic contact characteristics can be identified through a measurement step upstream of the processing step. Subsequently, for these regions, modified parameters of the voltage reversed from the forward direction of the silicon solar cell and the irradiation intensity of the point light source are set in the processing step. Alternatively, only sections with poor ohmic contact characteristics can be processed in the processing step, while sections exhibiting good ohmic contact characteristics can be skipped.

[0017] For example, the detection of the measured current downstream of the processing step can be used as a quality characteristic of the silicon solar cells in the solar module for further processing.

[0018] By detecting the measurement current before and after the processing steps, the improvement in ohmic contact characteristics achieved by the processing steps can be determined spatially with precision. With constant voltage and irradiation intensity parameters, the improvement in ohmic contact characteristics is visible as an increase in the measurement current. This also allows for the identification of zones where the target value for good ohmic contact characteristics between the contact grid and the emitter layer may not yet be achieved, thus enabling targeted implementation of further processing steps limited to these zones.

[0019] Furthermore, the processing current measured at the location during the processing step can be used to set the parameters of the processing step itself. For example, the current intensity corresponding to a certain processing location can be used as an adjustment variable to set the irradiation intensity and / or irradiation duration of the point light source and / or the voltage level opposite to the forward direction of the silicon solar cell when irradiating a subsequent processing location in the same processing step.

[0020] Advantageously, in the processing step, when one of the processing areas is irradiated, a first current intensity is detected using an ammeter, followed by a second current intensity, and these two current intensities are stored corresponding to that processing area. Subsequently, a current intensity gradient can be calculated from these two current intensities for the corresponding processing area. This current intensity gradient can be used as a measure of the improvement in ohmic contact characteristics achieved by the processing step for each processing area. Here, the current intensity gradient can also be used in the processing step to adjust parameters of downstream processing areas, or it can be used in entirely downstream processing steps.

[0021] In addition to detecting the intensity of the measuring or processing current during irradiation, the reverse current of the silicon solar cell can also be detected in upstream and / or downstream measurement steps and / or in processing steps when the silicon solar cell is not irradiated, and stored correspondingly to the respective processing and / or measurement locations. The value of the reverse current is suitable for evaluating potential damage to the silicon solar cell caused by processing steps with unfavorable parameters. The reverse current is evaluated against a reference value, for example, compared to a reverse current value obtained from electrical characterization (e.g., recording the IU characteristic curve) of the upstream silicon solar cell of the present invention. For example, if the reverse current measured by the method of the present invention is greater than the reverse current value obtained from previous electrical characterization, this may indicate damage to the silicon solar cell due to unfavorable parameters when the improved method is applied. Such damage may, for example, be the formation of a short circuit inside the silicon solar cell, which can be identified by an increase in the reverse current of the silicon solar cell.

[0022] In addition to using the reverse current value generated from the previous electrical characterization, the reference value can also be the reverse current detected in a measurement step upstream of the processing step. Alternatively, the reverse current can be measured in the processing step before at least a portion of the processing area is irradiated.

[0023] In an advantageous implementation, the deviation of the reverse current from a corresponding reference reverse current can also be used as an adjustment variable to set the irradiation intensity and / or the duration of irradiation and / or the level of the voltage reversed to the forward direction of the silicon solar cell when irradiating at least a portion of the localized treatment area. Similarly, rejection criteria for silicon solar cells can be provided by determining the limit value of the reverse current after the treatment step, and / or by determining the limit value of the change in reverse current caused by the treatment step, thereby removing the corresponding silicon solar cells from further processing and preventing them from being, for example, installed in solar modules.

[0024] When detecting reverse current during a measurement or processing step, a voltage reversed to the forward direction and less than the breakdown voltage of the silicon solar cell can be changed. Thus, a reverse current is measured for each preset voltage and stored corresponding to the respective measurement or processing location. This type of damage to the silicon solar cell can be identified by the change in the reverse voltage, thereby distinguishing, for example, damage in the form of cracks in the silicon solar cell from damage caused by increased carrier recombination.

[0025] In other technical solutions of the method, during the processing and / or measurement steps, when at least a portion of the processed or measured area is irradiated, the irradiation component reflected from the sun-facing side of the silicon solar cell is detected by measurement and stored corresponding to the respective area. This also allows for the identification of changes in optical properties caused by the processing steps.

[0026] When irradiating the measurement area in the measurement step and / or the processing area in the processing step, preferably, the wavelength of the light radiation emitted by the point light source is changed, and the current intensity is detected in the measurement step and / or processing step for the same light radiation, and stored in correspondence with the corresponding area.

[0027] When measuring the current intensity of the current and / or the processing current and / or the reverse current, it is advantageous to use the same ammeter. However, the invention is not limited to this. Depending on the specific measurement area, different measuring instruments may also be used. For example, the current intensity of the processing current differs from that of the reverse current by orders of magnitude; therefore, it is reasonable to use two ammeters optimized for the corresponding areas.

[0028] Different embodiments of the present invention will be described below.

[0029] First embodiment:

[0030] In the method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell according to the present invention, a silicon solar cell comprising an emitter layer, a contact grid, and a back contact is first provided. This can be, for example, a polycrystalline silicon solar cell with dimensions of 15.7 cm × 15.7 cm positioned on a processing table. The contact grid is then electrically connected to one electrode of a voltage source by means of a contact device, and the back contact is connected to the other electrode of the voltage source. The contact device can, for example, have spring-loaded pins that lie flat on the contact grid or back contact of the silicon solar cell and are connected to the voltage source via a cable.

[0031] In the first measurement step, a voltage oriented in the forward direction of the silicon solar cell is applied between the contact grid and the back contact via a voltage source using a contact device. While this voltage is applied, each measurement section of the solar cell's sun-facing side is illuminated with a point light source. This point light source can be, for example, a laser or a focused white light source. Illumination induces a measurement current within the corresponding section, wherein the applied voltage and the illumination intensity of the point light source are set such that this measurement current has a value of 1 mA / cm² for the measurement section. 2 Up to 500 mA / cm 2 The current density is determined. To illuminate each measurement location, light emitted from a point light source is now guided between each measurement location, with the applied voltage and the illumination intensity of the point light source remaining constant. The current in the silicon solar cell is now measured at each measurement location using an ammeter and a contact device, where the detected current intensity of the corresponding measurement current is stored in correspondence with the corresponding measurement location. The correspondence between the measured current intensity and the corresponding measurement location is achieved by, for example, storing the coordinates of the measurement location's position on the sun-facing side of the silicon solar cell for the corresponding current intensity.

[0032] In the processing step following the first measurement step, a voltage less than the breakdown voltage of the silicon solar cell, reversed from the forward direction, is applied using a voltage source and a contact device. When this voltage is applied, a point light source, already applied in the measurement step, is directed onto the sun-facing side of the silicon solar cell, illuminating a localized section of that sun-facing side. Irradiation induces a measurement current within the corresponding section. This current, for that specific section, has a current of 200 A / cm². 2 Up to 20000 A / cm 2A current density of 10 ns to 10 ms is applied to the region. Within this parameter range, the current intensity and application time are set by the moving speed of the point light source relative to the silicon solar cell, the illumination intensity of the point light source, and the level of the voltage reversed to the forward direction of the silicon solar cell (but smaller relative to the breakdown voltage). Through this processing step, the ohmic contact characteristics between the contact grid and the emitter layer of the silicon solar cell are significantly improved, especially in areas with high contact resistance between the contact grid and the emitter layer before the processing step.

[0033] Following this processing step, a second measurement step, similar to the first measurement step, is performed. Preferably, the current intensity of the measurement current is detected again under the same voltage and irradiation intensity parameters as in the first measurement step, and stored corresponding to the respective measurement location. For each measurement location, there is now only one measurement current intensity value before the processing step and one measurement current intensity value after the processing step. The spatially resolved quantification of the improved ohmic contact characteristics between the contact grid and the emitter layer is obtained from the change in the value of the corresponding measurement current. The change calculated from the measurement current is also stored corresponding to the respective measurement location. Subsequently, depending on the specific result obtained (change in the intensity of the measurement current), the silicon solar cell can be sent to another processing step. Subsequently, in this other processing step, for example, only the processing locations where the corresponding measurement location has not yet reached the preset measurement current change and / or the preset measurement current target value in the measurement step are processed.

[0034] The voltage applied in the measurement step can be opposite to the forward direction of the silicon solar cell and less than the breakdown voltage of the silicon solar cell, or the voltage applied in the measurement step can be oriented along the forward direction of the silicon solar cell.

[0035] Second embodiment:

[0036] The measurement steps are performed similarly to the first embodiment. However, the difference lies in the processing step, where the parameters of the reverse-current voltage and the illumination intensity of the point light source are adjusted based on the current intensity of the measured current detected in the first measurement step. In the processing step, regions with lower measured current intensities in the first measurement step are processed with a stronger processing current intensity and / or a longer processing current duration than regions where the measured current intensity is already higher. The processing current can be increased by increasing the reverse-current voltage and / or increasing the illumination intensity of the point light source. The extension of the processing current duration is controlled by the dwell time of the point light source on the corresponding processing area.

[0037] Third embodiment:

[0038] Similarly, in this measurement step, the measurement current when the measurement area is irradiated is detected, and the processing steps are performed accordingly. Furthermore, in the second measurement step, before and / or after irradiating at least a first portion of the measurement area, the sun-facing side of the silicon solar cell is kept unirradiated, and a voltage less than the breakdown voltage of the silicon solar cell is applied between the contact grid and the back contact using a voltage source, in the reverse direction of the voltage application. The reverse current of the silicon solar cell is then detected by an ammeter when the voltage is applied. This reverse current is then stored corresponding to the respective measurement area. In this case, the corresponding reverse current can be used as a characteristic value indicating potential damage to the silicon solar cell caused by the processing steps. For this purpose, the measured reverse current of the measured measurement area is compared with a reference reverse current obtained from the electrical characterization of the silicon solar cell upstream of the method. This electrical characterization may, for example, refer to the IU characteristic curve recorded when determining the solar cell efficiency, a process commonly used in the manufacturing process of silicon solar cells. Advantageously, in the measurement step, the reverse current is measured before or after irradiating all measurement areas.

[0039] The change in the reverse current measured in the second measurement step relative to the previously measured reference reverse current is used as a measure of the damage caused to the silicon solar cell by the processing step. If the reverse current of the silicon solar cell increases after the processing step, it can be inferred that the processing step has caused damage to the silicon solar cell.

[0040] Fourth embodiment:

[0041] The procedure of the method is similar to that of the third embodiment. However, the difference lies in that a reference reverse current is generated in the first measurement step. For this purpose, as in the second step, the sun-facing side of the silicon solar cell is kept un-illuminated before and / or after irradiating at least a first portion of the measurement area, thereby detecting the reverse current of the silicon solar cell with an ammeter when a voltage is applied. In this case, the change in the reverse current detected in the second measurement step relative to the reverse current detected in the first measurement step serves as a measure of potential damage to the silicon solar cell caused by the treatment steps.

[0042] Fifth embodiment:

[0043] In addition to detecting the measured current and / or reverse current in the measurement step, or as an alternative, the actual current intensity of the processing current is also detected for at least a portion of the irradiated processing area in the processing step, and stored correspondingly for the respective processing area. The current intensity is detected when the current's duration of action on the corresponding section ends. The processing current detected for the processing area is used as a measure of the improvement in ohmic contact characteristics between the contact grid and the emitter layer achieved by the processing step. If the processing area is processed with the same voltage reversed to the forward direction of the silicon solar cell and the same irradiation intensity parameters of the point light source, a region with better ohmic contact characteristics between the contact grid and the emitter layer can be observed because the current intensity is greater at the end of processing for the corresponding processing area. The processing current detected and stored for each processing area is used, for example, as a quality characteristic in subsequent processing of the silicon solar cell. Further processing steps can also be implemented using the detected and stored processing current, where, for example, in a further processing step, the region with the smaller measured processing current is selectively processed again with modified parameters. The modified parameters here refer to the intensity of the point light source and / or the duration of the illumination and / or the level of the voltage reversed to the forward voltage of the silicon solar cell.

[0044] Sixth embodiment:

[0045] If, unlike the fourth embodiment, a measurement step is not performed before the processing step, a reference reverse current can still be determined in the processing step for comparison with the reverse current measured in the second measurement step. For this purpose, in the processing step, the sun-facing side of the silicon solar cell is kept un-illuminated before irradiating the processing area, and the reverse current is detected when a voltage reversed from the forward direction of the silicon solar cell is applied.

[0046] Seventh embodiment:

[0047] Unlike the previous embodiments, the reference reverse current and the reverse current after processing the localized area can be measured only during the processing step. Therefore, in the processing step, the sun-facing side of the silicon solar cell is kept un-illuminated before irradiating the first portion of the processed area, and the reverse current is detected when a voltage reversed from the forward direction is applied. Subsequently, the first portion of the processed area is gradually irradiated. When irradiation of the first portion of the processed area ends, the sun-facing side of the silicon solar cell is again kept un-illuminated, and the reverse current is detected again. In this case, the value of the reverse current detected before irradiating the first portion of the processed area is used as a reference value for the reverse current detected after irradiating the first portion of the processed area.

[0048] If, during the processing steps, a point light source is used to scan the sun-facing side of the silicon solar cell row by row during local processing, the processing areas arranged along each row are irradiated sequentially. After each row is irradiated, the point light source is either turned off or, while still on, moved away from the sun-facing side of the silicon solar cell beyond its edge, so that the sun-facing side of the silicon solar cell is completely unirradiated, and reverse current can be detected when a voltage reversed from the forward direction is applied. In this case, the reverse current detected after irradiating one row is used as a reference reverse current for the reverse current generated after irradiating the next row. Thus, it is even possible to correlate potential damage to the silicon solar cell with the processing of a specific row (or processing area).

[0049] Eighth embodiment:

[0050] The processing is performed similarly to that in the seventh embodiment. Furthermore, the change in reverse current generated before and after irradiating one row is used as an adjustment variable for the parameters (irradiation intensity of the point light source, irradiation duration, and the level of the reverse voltage) set when irradiating the next row in the processing step. If an increase in reverse current is detected, the parameters (e.g., the irradiation duration) are changed when irradiating the next row to prevent further increase in reverse current.

[0051] In all the foregoing embodiments, as another implementation, when detecting the reverse current in the measurement or processing step, this reverse voltage can be changed as long as it is always less than the breakdown voltage of the silicon solar cell. Thus, a reverse current is measured for each preset voltage and stored corresponding to the corresponding measurement or processing location.

[0052] Ninth embodiment:

[0053] The processing current detected in the processing step (see fifth embodiment) is used to adjust parameters when processing subsequent processing areas. During this process, adjustments are performed such that the processing current detected when processing a processing area is compared with a reference value. If the detected processing current is less than this reference value, it may indicate that the improvement in the ohmic contact characteristics between the contact grid and the emitter layer is insufficient. Therefore, in the next processing area, the parameters for irradiating this processing area are adjusted accordingly.

[0054] Tenth embodiment:

[0055] Unlike the fifth embodiment, which detects the current intensity when the current's duration of action on the corresponding partition ends, here, when irradiating a processing area, a first current intensity is first detected using an ammeter for each processing area, followed by a second current intensity, and these two current intensities are stored corresponding to the processing area. The change in current intensity (gradient) is used as a measure of the improvement in the ohmic contact characteristics between the contact grid and the emitter layer. An increase in current intensity during the irradiation of a processing area indicates an improvement in ohmic contact characteristics. A small increase or no increase in current intensity indicates only a small improvement or no improvement in ohmic contact characteristics. Therefore, the change in current intensity during the irradiation of a processing area is used to adjust parameters of at least one subsequent processing area (irradiation intensity of the point light source, irradiation duration, and the level of the reverse and forward voltages). In addition to using the gradient of current intensity as an adjustment variable, this gradient is also stored corresponding to the corresponding processing area.

[0056] In all the listed embodiments, optionally, during the processing and / or measurement steps, when at least a portion of the processing or measurement area is irradiated, the irradiation component reflected from the sun-facing side of the silicon solar cell is detected by measurement and stored corresponding to the respective area. Furthermore, optionally, when detecting the reflection component, the wavelength of the light radiation emitted by the point light source is changed, wherein a preset wavelength of reflection component is detected and stored corresponding to the respective area. When detecting the current intensity of the measurement current and / or processing current, optionally, the wavelength of the light radiation emitted by the point light source is also changed, wherein a preset wavelength of measurement current and / or processing current is also detected and stored corresponding to the respective area.

Claims

1. A method for improving the ohmic contact characteristics between the contact grid and the emitter layer of a silicon solar cell, wherein in a processing step, a voltage less than the breakdown voltage of the silicon solar cell, reversed from the forward direction of the silicon solar cell, is applied between the contact grid and the back contact of the silicon solar cell using a voltage source and a contact device connected to the voltage source; and, when the voltage is applied, a point light source is guided within a region on the sun-facing side of the silicon solar cell; and, during this process, a processed area of ​​the sun-facing side is irradiated, thereby generating a processing current in the corresponding area by induction; and, the processing current having a value of 200 A / cm for the processed area. 2 Up to 20000 A / cm 2 The current density is applied to the partition at a time of 10 ns to 10 ms, characterized in that... A measurement step is performed before and / or after the processing step, in which a voltage is applied between the contact grid and the back contact using the voltage source and the contact device, and, while the voltage is applied, a measurement section of the sun-facing side of the silicon solar cell is illuminated with the point light source, thereby inducing a measurement current within the corresponding section, the measurement current having a value of 1 mA / cm² for the measurement section. 2 Up to 500 mA / cm 2 The current density is measured using an ammeter, and the current intensity of the measured current is stored corresponding to the corresponding measurement location. The current intensity measured by the corresponding measurement location is used as an adjustment variable for subsequent processing steps of the silicon solar cell.

2. The method according to claim 1, characterized in that, During the processing step, the current intensity of the processing current is detected by an ammeter for at least a portion of the irradiated processing area, and stored in correspondence with the corresponding processing area.

3. The method according to claim 1 or 2, characterized in that, The voltage applied in the measurement step is opposite to the forward direction of the silicon solar cell and less than the breakdown voltage of the silicon solar cell, or the voltage applied in the measurement step is oriented along the forward direction of the silicon solar cell.

4. The method according to claim 1 or 2, characterized in that, The current intensity corresponding to a certain measurement location in the measurement step is used as an adjustment variable to set the irradiation intensity of the point light source and / or the duration of the irradiation and / or the level of the voltage opposite to the positive direction of the silicon solar cell when irradiating at least one of the processing locations in the processing step after the measurement step.

5. The method according to claim 1 or 2, characterized in that, The change is determined by the current intensity detected by one of the measurement localities in a measurement step upstream of the processing step and the current intensity detected by the measurement locality in a measurement step downstream of the processing step, and the change is stored in correspondence with the respective measurement locality.

6. The method according to claim 5, characterized in that, The change in current intensity corresponding to a certain measurement locality is used as an adjustment variable in another processing step to set the irradiation intensity of the point light source and / or the duration of the irradiation and / or the level of the voltage opposite to the positive direction of the silicon solar cell when irradiating at least one of the processing localities.

7. The method according to claim 1 or 2, characterized in that, In the processing step, the current intensity corresponding to a certain processing location is used to set the irradiation intensity of the point light source and / or the duration of the irradiation and / or the level of the voltage opposite to the positive direction of the silicon solar cell when irradiating the subsequent processing location of the processing step.

8. The method according to claim 1 or 2, characterized in that, In the processing step, when one of the processing areas is irradiated, a first current intensity is detected with an ammeter, followed by a second current intensity, and the two current intensities are stored in correspondence with the processing area.

9. The method according to claim 8, characterized in that, The current intensity gradient is determined from the first and second current intensities and stored in local correspondence with the processing.

10. The method according to claim 9, characterized in that, In the processing step, the current intensity gradient corresponding to the processing locality is used as an adjustment variable to set the irradiation intensity and / or the irradiation duration and / or the level of the voltage opposite to the positive direction of the silicon solar cell when irradiating the subsequent processing locality in the processing step.

11. The method according to claim 1 or 2, characterized in that, In the processing step, before and / or after irradiating at least a first portion of the processed area, the sun-facing side of the silicon solar cell is not irradiated, during which the reverse current of the silicon solar cell is detected using the ammeter.

12. The method according to claim 1 or 2, characterized in that, In the measurement step, before and / or after irradiating at least a first portion of the measurement area, the sun-facing side of the silicon solar cell is not irradiated, and a voltage reversed to the forward direction and less than the breakdown voltage of the silicon solar cell is applied by the voltage source between the contact grid and the back contact via the contact device. During this process, the reverse current of the silicon solar cell is detected by the ammeter and stored corresponding to the measurement area.

13. The method according to claim 11, characterized in that, The reverse current is compared with a reference reverse current, and the deviation between the reverse current and the reference reverse current is used as an adjustment variable to set the irradiation intensity and / or the duration of the irradiation and / or the level of the voltage opposite to the forward voltage of the silicon solar cell when another part of the local area irradiating the sun-facing side of the silicon solar cell is irradiated.

14. The method according to claim 13, characterized in that, The reference reverse current is obtained from the electrical characterization of the silicon solar cell upstream of the method.

15. The method according to claim 13, characterized in that, The reverse current detected before irradiating the first part of the irradiated treatment area in the processing step is used as a reference reverse current for the reverse current detected after irradiating the first part of the irradiated treatment area.

16. The method according to claim 15, characterized in that, The reference reverse current used for processing a local area in the processing step is the reverse current measured for a certain measurement locality in the measurement step upstream of the processing step.

17. The method according to claim 11, characterized in that, In the measurement step and / or the processing step, in order to detect the reverse current, the voltage reversed from the forward current and less than the breakdown voltage of the silicon solar cell is changed.

18. The method according to claim 1 or 2, characterized in that, In the processing step and / or the measurement step, when at least a portion of the processing area or the measurement area is irradiated, the irradiation component reflected from the sun-facing side of the silicon solar cell is detected by measurement and stored corresponding to the respective area.

19. The method according to claim 18, characterized in that, In the processing step and / or the measurement step, when at least a portion of the processing area or the measurement area is irradiated, the wavelength of the light radiation emitted by the point light source is changed, and at the same wavelength, the irradiation component reflected from the sun-facing side of the silicon solar cell is detected by measurement and stored corresponding to the respective area.

20. The method according to claim 1 or 2, characterized in that, In the measurement step and / or the processing step, the wavelength of the light radiation emitted by the point light source is changed, and the current intensity is detected in the measurement step and / or the processing step for the same light radiation, and stored in correspondence with the corresponding local area.

21. The method according to claim 1 or 2, characterized in that, The ammeter is connected to the contact device, or to another contact device connected to the contact grid and back contact of the silicon solar cell.