CN112993062B - Flexible CIGS thin film battery with embedded grid line electrode - Google Patents

Abstract

The invention discloses a flexible CIGS thin film battery with an embedded grid line electrode, which comprises a CIGS light absorption layer and a transparent surface electrode layer, wherein the CIGS light absorption layer of the thin film battery is etched with a wire groove structure at the position of a silk-screen conductive grid line, the transparent surface electrode layer is provided with a downward convex linear groove at the position corresponding to the wire groove structure, the downward convex linear groove is embedded into the wire groove structure of the CIGS light absorption layer, the lower end part of the conductive grid line is embedded into the linear groove, and the upper end part of the conductive grid line extends upwards to the outside of the linear groove. The thin film battery of the invention can realize low resistance and good conductivity under the condition of small size of the grid line electrode on the upper surface of the battery by increasing the contact area of the grid line electrode and the transparent surface electrode layer.

Description

A flexible CIGS thin-film battery with embedded grid electrodes

technical field

The invention relates to a flexible CIGS thin film battery with embedded grid line electrodes.

Background technique

Solar cells can convert light into electrical energy, and each independent battery unit is connected in series to output electrical energy as a whole. The most direct indicator to evaluate the performance of a battery is the photoelectric conversion efficiency. There are many factors that affect the photoelectric conversion efficiency of photovoltaic cells, such as the differences between different types of photovoltaic materials, preparation processes, effective light-receiving area, and the power loss of the battery itself. Increasing the effective light-receiving area of the battery or reducing the power loss of the battery itself is considered to be an easier way to improve the photoelectric conversion efficiency of the battery. At present, the vast majority of photovoltaic cells use the method of printing electrodes on the top layer to prepare the battery output electrodes. The top electrode collects the charge and conducts the electric energy converted by the battery. The lower its own resistance, the smaller the power consumption of the battery. Therefore, the thicker and wider the electrode grid is required, the better. However, because the electrode grid is located on the top layer of the battery, the wider the grid will block more light, affecting the effective light-receiving area of the battery. Conversely, the thinner the electrode grid, the better. In order to solve this problem, the existing technology solves the mutual restriction between grid line resistance and shading area by adjusting the aspect ratio of the grid line (that is, the gate line is narrowed but the height is increased) or by using a busbar-free perforated back contact cell (commonly seen in crystalline silicon cells) or by using an ultra-dense busbar-free structure. The main grid is removed from the back contact cell, although the shading area is greatly reduced, but because the cell is tunneled by the laser hole, the risk of cracks is increased; adjust the grid line aspect ratio, that is, increase the aspect ratio on the existing printed pattern, so that the grid line becomes narrower but the height is increased. Since the light source is facing the battery in the standard battery efficiency test, the shading is mainly affected by the width of the grid line and has nothing to do with the height. The grid plus the thickness of the ribbon will block more oblique rays.

Contents of the invention

Purpose of the invention: The present invention aims at solving the problem of hidden crack risk or shading of oblique light in the prior art when solving the mutual restriction between grid electrode resistance and battery shading area, and provides a flexible CIGS thin-film battery with embedded grid electrodes. By increasing the contact area between the grid electrodes and the transparent surface electrode layer, the thin-film battery achieves low resistance and good electrical conductivity even when the size of the grid electrodes on the upper surface of the battery is small.

Technical solution: The flexible CIGS thin-film battery with embedded grid line electrodes according to the present invention, the thin-film battery includes a CIGS light-absorbing layer and a transparent surface electrode layer, the CIGS light-absorbing layer of the thin-film battery is etched with a wire groove structure at the position of the silk screen conductive grid line, and the transparent surface electrode layer is provided with a downwardly convex linear groove at a position corresponding to the wire groove structure, the downwardly convex linear groove is embedded in the wire groove structure of the CIGS light-absorbing layer, the lower end of the conductive grid line is embedded in the linear groove, and the upper end of the conductive grid line extends upward to Outside the linear groove.

Wherein, the thin-film battery sequentially includes a substrate, a back electrode layer, a reflective layer, a CIGS light-absorbing layer, a buffer layer, and a transparent surface electrode layer from bottom to top in the longitudinal direction; the transparent surface electrode layer includes a transparent surface electrode high impedance layer and a transparent surface electrode low impedance layer, and the conductive grid line includes a lower end located in a linear groove and an upper end extending out of the linear groove. The upper end of the conductive grid line is connected to the low-impedance layer, and the lower end of the conductive grid line is connected to the high-impedance layer.

Wherein, the cross section of the upper end of the conductive grid line is semicircular or rectangular, and the cross section of the lower end of the conductive grid line is rectangular.

Wherein, the upper end of the conductive grid line is a silver grid line; the lower end of the conductive grid line is a silver grid line or a silver grid line doped with sodium, and when it is a silver grid line doped with sodium, sodium is doped at the lower end of the silver grid line.

Wherein, the conductive grid line is screen-printed on the battery to form a grid line electrode; the grid line electrode is a grid line electrode containing at least one main grid line or a grid line electrode without a main grid line.

Wherein, the inner diameter of the linear groove corresponding to the thin grid line in the grid electrode is 49-79um, and the depth is 1.75-2.25um; the inner diameter of the linear groove corresponding to the main grid line in the grid electrode is 999-1499um, and the depth is 1.75-2.25um.

Wherein, the upper surface of the CIGS light-absorbing layer is also etched with a plurality of concave tooth structures, the plurality of concave tooth structures are arranged in a matrix, and the plurality of concave tooth structures arranged in a matrix are interposed between adjacent slot structures; the high-impedance layer has a plurality of convex structures corresponding to the concave tooth structures, the top of the convex structures is open and protrudes downward, and the convex structures of the high-impedance layer are embedded in the concave tooth structures on the upper surface of the CIGS light-absorbing layer. In the raised structure, the upper surface of the low-impedance layer is a continuous flat structure.

Wherein, the cross section of the concave tooth structure is rectangular or conical.

Wherein, an isolation strip is set at a distance of 0.1 to 1 mm from the outer edge of the battery, and the isolation strip and the corresponding battery edge are parallel to each other, and the isolation strip forms a ring around the periphery of the battery; the width of the isolation strip is 0.02 to 0.05 mm, and the depth of the isolation strip is from the upper surface of the battery to the upper surface of the substrate.

Wherein, the isolation zone is filled with insulating glue.

Beneficial effects: the thin-film battery of the present invention embeds the grid electrode inside the transparent surface electrode layer and the battery (CIGS absorbing layer), which effectively increases the contact area between the grid electrode and the transparent surface electrode layer, and is more conducive to the collection of electrons from the depth of the transparent electrode layer by the grid electrode. In this way, the internal resistance of the battery is reduced, that is, the loss of battery power is reduced, thereby increasing the output power of the battery and improving the photoelectric conversion efficiency; Cause resistance to increase, and the thickness of the grid lines on the battery surface can also be reduced, thereby effectively reducing the shading effect of the grid lines on the battery surface on vertical and oblique illumination, thereby increasing the effective light-receiving area of the battery; The electrodes can quickly conduct the heat generated by the battery from the inside to the surface of the battery and dissipate it, thereby effectively reducing the temperature of the battery and ensuring the stability of the battery's power generation performance.

Description of drawings

FIG. 1 is a schematic structural view of a thin-film battery according to Embodiment 1 of the present invention;

Fig. 2 is a sectional view of Fig. 1a-a;

Fig. 3 is a sectional view of Fig. 2b-b;

4 is a schematic structural view of a thin-film battery according to Embodiment 2 of the present invention;

Fig. 5 is a sectional view of Fig. 4c-c;

Fig. 6 is a sectional view of Fig. 5d-d;

7 is a schematic structural view of a thin film battery according to Embodiment 3 of the present invention;

Figure 8 is a sectional view of Figure 7e-e;

Figure 9 is a sectional view of Figure 8f-f;

Fig. 10 is the shading situation of the embedded grid line electrode to the light;

Figure 11 is a comparison of the shading conditions of the conventional grid line and the grid line electrode of the present invention for oblique illumination;

Fig. 12 is a schematic diagram of light entering the light absorbing layer after multiple reflections in the light trapping structure;

Fig. 13 is a principle diagram of effectively increasing the area of the PN junction interface between the transparent surface electrode layer and the light absorbing layer by the light trapping structure;

Fig. 14 is a top view of the thin film battery of the present invention;

Figure 15 is a sectional view of Figure 14G-G;

Fig. 16 is a schematic diagram of sodium diffusion of sodium-doped silver grid lines.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figures 1 to 3, the present invention has a flexible CIGS thin-film battery 100 with embedded grid electrodes. The thin-film battery 100 includes a substrate 1, a back electrode layer 2, a reflective layer 3, a CIGS light-absorbing layer 4, a buffer layer 5, and a transparent surface electrode layer from bottom to top in the longitudinal direction; wherein, the transparent surface electrode layer includes a transparent surface electrode high-impedance layer 6 and a transparent surface electrode low-impedance layer 7; the CIGS light-absorbing layer 4 is etched with a wire groove structure 4-1 at the position of the silk screen conductive grid line 10, and the inner side of the wire groove structure 4-1. After the buffer layer 5 and the transparent surface electrode layer are deposited sequentially on the bottom, the transparent surface electrode layer forms a downwardly convex linear groove 62 at a position corresponding to the wire groove structure 4-1. The downwardly convex linear groove 62 is located in the wire groove structure 4-1 of the CIGS light absorbing layer, and the conductive grid lines 10 are silk-printed into the linear groove 62. The conductive grid line 10 includes a part extending from the linear groove 62 - an upper end 10-2 and a part located in the linear groove 62 - a lower end 10-1. The lower end 10-1 of the conductive grid line 10 is embedded in the linear groove 62, and the upper end 10-2 of the conductive grid line 10 extends upwards to outside the linear groove 62 (the upper end 10-2 of the conductive grid line 10 is located on the upper surface of the thin film battery). The upper end 10 - 2 of the conductive grid line 10 is connected to the low impedance layer 7 , and the lower end 10 - 1 of the conductive grid line 10 is connected to the high impedance layer 6 .

The upper surface of the CIGS light-absorbing layer 4 is also etched with a plurality of concave tooth structures 4-2, the plurality of concave tooth structures 4-2 are arranged in a matrix, and the multiple concave tooth structures 4-2 arranged in a matrix are interposed between adjacent line groove structures 4-1 (adjacent line groove structures 4-1 are arranged parallel to each other); the high impedance layer 6 has a plurality of convex structures 61 corresponding to the concave tooth structures 4-2, the top of the convex structure 61 is open and protrudes downward, and the convex structure 61 of the high impedance layer 6 is embedded in the CIGS light absorbing layer 4 In the concave tooth structure 4-2 on the upper surface, the lower surface of the low-impedance layer 7 is formed with a plurality of raised blocks 71 corresponding to the raised structures 61, and the raised blocks 71 are embedded in the raised structure 61 with the top opening. The upper surface of the low-impedance layer 7 is in a flat and continuous structure in the region 4-3 where the CIGS light absorbing layer 4 is provided with a plurality of concave tooth structures 4-2. After a buffer layer is deposited inside the concave tooth structure 4-2, the concave tooth structure 4-2 is filled with a transparent surface conductive layer.

As shown in Figures 12 to 13, the thin film battery of the present invention forms multiple light-trapping structures through the concave tooth structure 4-2, that is, the transparent surface electrode layer and the light-absorbing layer are no longer in planar contact, but intersected with each other. The block structure is inserted downward into the convex structure depressed downward on the high resistance layer. This interlocking structure forms a microscopic light-trapping structure inside the thin-film battery. When light enters, it undergoes multiple reflections at the interlocking interface, which can increase light absorption; light that passes through the light-absorbing layer and is not completely absorbed is reflected by the reflective layer at the bottom of the light-absorbing layer and reenters the light-absorbing layer. Part of it will be absorbed again. Afterwards, if there are still unabsorbed light that escapes from the light-absorbing layer and passes through the interlocking interface again, it will still be reflected multiple times to increase light absorption. This light-trapping structure is located inside the battery, and the surface of the battery has only a slight pit structure, so the light-trapping effect is increased without reducing the conductivity of the surface electrode layer. At the same time, the tooth structure of the film layer inside the battery greatly increases the area of the PN junction interface. In addition to forming the PN junction interface on the upper and lower sides of each tooth structure, the side of the tooth structure can also form a PN junction interface, so that the excitons or carriers located in the tooth structure on the upper part of the light absorbing layer have more opportunities to diffuse to the PN junction interface to form photovoltaic currents. Secondly, because the tooth structure of the transparent surface electrode layer goes deep into the lower part of the light-absorbing layer (that is, the PN junction formed at the bottom of the tooth structure goes deep into the lower part of the light-absorbing layer), the excitons or carriers that were difficult to migrate long-distance in the lower part of the light-absorbing layer in the past also have the opportunity to generate current near the PN junction. In the end, more carriers have more opportunities to participate in power generation, which greatly improves the utilization rate of carriers, which means that the current density increases and the short-circuit current of the battery increases. The tooth structure of the high-impedance layer of the transparent electrode that penetrates into the light-absorbing layer, and the tooth structure of the low-impedance layer that penetrates into the tooth structure of the high-impedance layer have a better transport effect on the electrons collected from the inside of the light-absorbing layer, which reduces the internal resistance of the thin-film battery again, increases the output power of the battery, and improves the fill factor. The concave-convex structure can also reduce the material used for the transparent electrode layer and save the cost of the target material, and the thinner surface transparent electrode layer can further increase the incident light. The thin film battery of the invention has the characteristic of high carrier utilization rate.

In FIG. 2 , the cross section of the upper end 10 - 2 of the conductive grid line 10 is semicircular, and the cross section of the lower end 10 - 1 of the conductive grid line 10 is rectangular. The conductive grid line 10 is a silver grid line, or the upper end 10-2 of the conductive grid line 10 is a silver grid line, and the lower end 10-1 of the conductive grid line 10 is a silver grid line doped with sodium. As shown in Figure 16, sodium is doped at the end of the lower end 10-1 of the conductive grid line 10. The sodium source is located in the concave teeth 4-2 of the CIGS light absorption layer 4. Sodium can directly diffuse deep into the CIGS light absorption layer 4. In addition to downward diffusion, it can also diffuse from the sides of the concave teeth 4-2 to the surroundings (diffusion in the CIGS light absorption layer 4), and finally form sodium doping with a deeper depth and wider range in the CIGS light absorption layer 4, thereby reducing the defect density of the CIGS light absorption layer 4, increasing the carrier concentration, and further improving the battery. efficiency. The doped sodium is concentrated at the end of the silver grid line, and the upper silver grid line does not contain sodium, which avoids the lateral diffusion of sodium on the transparent electrode layer on the battery surface and affects the structural stability of the transparent electrode layer.

Conductive grid lines 10 are silk-printed on the battery to form a grid line electrode 80; the embodiment is a grid line electrode 80 containing a main grid 11, the inner diameter of the line groove structure corresponding to the thin grid line 12 in the grid line electrode 80 is 49-79um, and the depth is 1.75-2.25um; the inner diameter of the line groove structure corresponding to the main grid line 11 in the grid line electrode 80 is 999-1499um, and the depth is 1.75-2.25um.

The flexible CIGS thin film battery of the present invention is prepared by the following method, and the specific steps are:

(1) Choose a stainless steel substrate with a thickness of 0.05-0.2mm, preferably 0.1-0.15mm, and use acetone to scrub and clean it to facilitate coating;

(2) Deposit 0.5-1.5um, preferably 0.8-1um thick metal molybdenum (Mo) on the stainless steel substrate by magnetron sputtering as the back electrode layer, and then deposit a 0.1um thick conductive reflective layer thereon;

(3) Using the low-temperature vacuum magnetron sputtering method, CIGS multi-component alloy is used as the target material, and a layer of 1.5-2.5um, preferably 2um thick CIGS light-absorbing layer is deposited on the conductive reflective layer;

(4) In a vacuum environment, using a pulsed laser etching process, a plurality of concave tooth structures are evenly etched on the upper surface of the CIGS light-absorbing layer according to the designed etching pattern. Each concave tooth structure is an independent structure. , where the width of the line groove under the busbar is 1000-1500um, and the finally formed line groove pattern and the top-layer conductive grid line pattern correspond one-to-one and the vertical projection coincides;

(5) The CIGS light absorption layer with a concave teeth structure and the groove structure is a 50-100nm thick buffer layer on the magnetic sputtering layer. The material is cadmium sulfide or other cadmium -free materials. The pulse laser etching off the concave teeth and some buffer layer in the wire groove is only 50 to 100Nm thick buffer layer. At this time, The diameter becomes 9.8um ~ 9.9um, and the corresponding wire groove width has also narrowed a little, and finally forms a buffer layer evenly on the surface of the concave teeth and the surface of the wire groove;

(6) Use vacuum magnetron sputtering to deposit a layer of about 0.5um thick transparent surface electrode sublayer-high impedance layer on the buffer layer. The material can be intrinsic zinc oxide ZnO or indium tin oxide ITO. Use pulse laser to etch away part of the high resistance material in the concave teeth, leaving only about 0.5um thick high impedance layer, and the diameter of the concave teeth is further reduced to 8.8um ~ 8.9um. In this step, the high resistance material in the line groove does not need to be etched;

(7) On the high-impedance layer, a layer of transparent surface electrode sublayer-low-impedance layer about 1um thick is deposited by vacuum magnetron sputtering method, which will fill the concave teeth and leave slight pits on the upper surface of the battery. The material can be selected from aluminum-doped zinc oxide ZAO or indium zinc tin oxide IZTO. Afterwards, after vacuum high-temperature annealing treatment, the material of each film layer inside the battery is restructured and crystallized, and the absorbing layer has a chalcopyrite structure. Since then, the sputtering coating process has been completed.

(8) In the grid line electrode area on the low-impedance layer of the transparent surface electrode, through the pulse laser etching process again, grooves are made from the low-impedance layer to the high-impedance layer, and the depth reaches the bottom of the high-impedance layer line groove, but both sides and bottom do not touch the buffer layer, and finally form a small wire groove with a width of 49-79um and a depth of 1.75-2.25um and a large wire groove with a width of 999um-1499um and a depth of 1.75-2.25um.

(9) Select low-temperature conductive silver paste as the grid wire electrode material, and use a printing screen that is consistent with the wire groove pattern on the battery surface (the width of the screen is slightly narrower than the wire groove) for the first screen printing. After a short drying, use a printing screen that is slightly wider than the wire groove for the second screen printing to complete the electrode printing on the battery surface so that the silver paste completely fills the wire groove to form a grid wire electrode with a T-shaped structure. Both printings use low-frequency ultrasonic equipment to process the printed cells, which helps the silver paste to be fully embedded in the wire groove.

(10) Sinter the printed battery sheet at a low temperature at about 200 degrees Celsius to dry and solidify the silver paste to form an ohmic contact with the transparent conductive layer of the thin film battery.

(11) Finally, use a fully automatic graphic scribing machine, use a high-precision needle, and perform scribing processing along its periphery at a distance of 0.1mm-1mm (preferably 0.2-0.5mm, most preferably 0.3mm) from the edge of the battery, and describe the isolation zone 90 with a width of 0.02-0.05mm and a depth reaching the upper surface of the stainless steel substrate (as shown in Figures 14-15), and the battery has been prepared since then.

Most of the leakage current caused by edge defects is due to the low resistance caused by the thin film layer or the dislocation of defects on the vertical surface of each layer of the film, which causes the upper transparent conductive layer to be connected to the back electrode layer or the stainless steel substrate. As long as the coating film at a distance of 0.1 mm to 1 mm from the edge of the battery is removed from the substrate along a path parallel to the edge of the battery, a battery with a circle of isolation band 90 (the width of the isolation band 90 is 0.02 to 0.05 mm and the depth is 2 to 4 um, or the depth of the isolation band depends on the total thickness of the coating) can be obtained. The isolation strip 90 is deep enough to reach the upper surface of the substrate 1. During the subsequent component packaging stage of the battery, the adhesive film is melted and filled into the isolation strip 90. Therefore, the isolation strip 90 will be filled with an adhesive film layer, and the insulation and isolation effect of the battery will be further strengthened. Edge defects no longer affect the normal area in the middle of the battery, completely eliminating the impact of leakage. Therefore, the isolation strip structure can effectively avoid the impact of edge defects on the normal area of the battery center, effectively reduce the leakage current of the entire battery, increase the parallel resistance of the battery, and then synergistically improve the photoelectric conversion efficiency of the battery, while reducing hot spots caused by edge leakage and improving battery life. A large number of tests have proved that the conversion efficiency of the battery with the isolation strip structure can be further increased by more than 0.2%, and the edge leakage hot spot phenomenon has also been significantly improved.

The pulse laser etching in the above steps can also be replaced by a patterned mask chemical etching process, which can also produce the required concave tooth and line groove structure; a laser scribing machine can also be used instead of high-precision needle scribing, and edge isolation zones can also be formed.

Example 2

As shown in FIGS. 4 to 6 , the only difference between the thin-film battery of Embodiment 2 and Embodiment 1 is that the gate electrode 80 of Embodiment 2 does not have the busbar 11 . When the grid electrode 80 does not contain the busbar 11, the light-receiving area of the battery will further increase. Since the embedded grid electrode is used, the conductivity of the grid electrode will not be greatly affected without the busbar. Compared with the existing grid electrode containing the busbar, the electrical conductivity is not much different, but it is far greater than the electrical conductivity of the existing battery without the busbar.

Example 3

As shown in Figures 7 to 9, the only difference between Example 3 and Example 1 thin-film battery is that the cross-section of the concave tooth structure on the CIGS light-absorbing layer in Example 1 is rectangular (in the top view 3, the concave tooth structure 4-2 is circular), and the cross-section of the concave tooth structure on the CIGS light-absorbing layer in Example 3 is conical (in the top view 9, the concave tooth structure 4-2 is square).

As shown in Figure 10, the lower end of the embedded grid electrode (that is, the enlarged area of the grid electrode) is embedded inside the battery. This area is originally an area where light is difficult to illuminate, so the enlarged area of the grid electrode has no additional impact on the light absorption of the battery.

As shown in Figure 11, comparing the cross-sections of the conventional grid lines and the grid lines of the present invention, the vertical shading area S3 and oblique shading area S4 of the grid line structure of the present invention are both smaller than the vertical shading area S1 and oblique shading area S2 of the conventional grid lines.

Claims (6)

1. A flexible CIGS thin-film battery with embedded grid line electrodes, characterized in that: the thin-film battery includes a CIGS light-absorbing layer and a transparent surface electrode layer, the CIGS light-absorbing layer of the thin-film battery is etched with a wire groove structure at the position of the silk screen conductive grid line, the transparent surface electrode layer is provided with a downwardly convex linear groove at a position corresponding to the wire groove structure, and the downwardly convex linear groove is embedded in the wire groove structure of the CIGS light-absorbing layer. Outside the linear groove; the transparent surface electrode layer includes a transparent surface electrode high-impedance layer and a transparent surface electrode low-impedance layer in turn. The conductive grid includes a lower end located in the linear groove and an upper end extending from the linear groove. The upper end of the conductive grid is connected to the low-impedance layer, and the lower end of the conductive grid is connected to the high-impedance layer; the cross section of the upper end of the conductive grid is semicircular, and the cross-section of the lower end of the conductive grid is rectangular; The silver grid line, when it is a silver grid line doped with sodium, the sodium is doped at the lower end of the silver grid line; the upper surface of the CIGS light-absorbing layer is also etched with a plurality of concave-tooth structures arranged in a matrix, and the multiple concave-tooth structures arranged in a matrix are interposed between adjacent line groove structures; the high-impedance layer has a plurality of convex structures corresponding to the concave-tooth structures. A plurality of raised blocks corresponding to the raised structure are formed, the raised blocks are embedded in the raised structure with the top opening, and the upper surface of the low-impedance layer has a continuous flat structure; The above-mentioned flexible CIGS thin-film battery is prepared by the following method, and the specific steps are: (1) Select a stainless steel substrate with a thickness of 0.05~0.2mm, and use acetone to scrub and clean it to facilitate coating; (2) Deposit 0.5~1.5um thick metal molybdenum on the stainless steel substrate by magnetron sputtering as the back electrode layer, and then deposit a 0.1um thick conductive reflective layer on it; (3) Using low-temperature vacuum magnetron sputtering method, CIGS multi-component alloy is used as the target material, and a 1.5~2.5um thick CIGS light-absorbing layer is deposited on the conductive reflective layer; (4) In a vacuum environment, using a pulsed laser etching process, a plurality of concave tooth structures are evenly etched on the upper surface of the CIGS light-absorbing layer according to the designed etching pattern. Each concave tooth structure is an independent structure. Slots, wherein the width of the slots below the main grid is 1000~1500um, and the finally formed slot pattern and the top-layer conductive grid line pattern correspond one-to-one and the vertical projection coincides; (5) Magnetron sputtering deposits a buffer layer with a thickness of 50-100nm on the CIGS light-absorbing layer with a concave tooth structure and a wire groove structure. The material is cadmium sulfide, and the pulse laser is used to etch away part of the buffer layer material in the concave teeth and wire grooves, leaving only a 50-100nm thick buffer layer. At this time, the inner diameter of the concave teeth becomes 9.8um~9.9um, and the corresponding wire groove width is also narrowed a little, and finally the upper surface of the concave teeth and wire grooves is evenly covered with a buffer layer; (6) Use vacuum magnetron sputtering to deposit a 0.5um thick transparent surface electrode sublayer on the buffer layer. The material is intrinsic zinc oxide ZnO or indium tin oxide ITO. Use pulse laser to etch away part of the high resistance material in the concave tooth, leaving only a 0.5um thick high impedance layer. The diameter of the concave tooth is further reduced to 8.8um~8.9um, and the high resistance material in the wire slot does not need to be etched; (7) On the high-impedance layer, a 1um-thick transparent surface electrode sub-layer is deposited by vacuum magnetron sputtering method, which will fill the concave teeth and leave slight pits on the upper surface of the battery. The material is selected to be doped with aluminum zinc oxide ZAO or indium zinc tin oxide IZTO; after that, after vacuum high-temperature annealing treatment, the materials of each film layer inside the battery are restructured and crystallized, and the sputtering coating process has been completed since then; (8) In the grid line electrode area on the low-impedance layer of the transparent surface electrode, the pulse laser etching process is used again to open grooves from the low-impedance layer to the high-impedance layer, and the depth reaches the bottom of the high-impedance layer line groove, but both sides and the bottom do not touch the buffer layer, and finally form a small wire groove with a width of 49~79um and a depth of 1.75~2.25um and a large wire groove with a width of 999um~1499um and a depth of 1.75~2.25um; (9) Select low-temperature conductive silver paste as the grid wire electrode material, use a printing screen that is consistent with the pattern of the wire slot on the battery surface for the first screen printing, and use a printing screen that is slightly wider than the wire slot for the second screen printing after drying to complete the electrode printing on the battery surface, so that the silver paste completely fills the wire slot to form a T-shaped grid electrode. Both printings use low-frequency ultrasonic equipment to process the printed cells, which helps the silver paste to be fully embedded in the wire slot; (10) Sinter the printed battery sheet at a low temperature at 200 degrees Celsius to dry and solidify the silver paste to form an ohmic contact with the transparent conductive layer of the thin film battery; (11) Finally, use a fully automatic graphic scribing machine and use a high-precision needle to scribe along the periphery of the battery at a distance of 0.1mm~1mm from the edge of the battery, depicting a width of 0.02~0.05mm and a depth of 0.02~0.05mm, and the depth reaches the isolation zone on the upper surface of the stainless steel substrate. Since then, the battery has been prepared. 2. The flexible CIGS thin-film battery with embedded grid electrodes according to claim 1, characterized in that: the thin-film battery sequentially comprises a substrate, a back electrode layer, a reflective layer, a CIGS light-absorbing layer, a buffer layer and a transparent surface electrode layer from bottom to top in the longitudinal direction. 3. The flexible CIGS thin-film battery with embedded grid electrodes according to claim 1, characterized in that: the conductive grid is screen-printed on the battery to form a grid electrode; the grid electrode is a grid electrode containing at least one busbar or the grid electrode is a busbar-free electrode. 4. The flexible CIGS thin-film battery with embedded grid electrodes according to claim 1, wherein the cross-section of the concave tooth structure is rectangular or tapered. 5. The flexible CIGS thin-film battery with embedded grid electrodes according to claim 1, characterized in that: an isolation strip is set at a distance of 0.1 to 1 mm from the outer edge of the battery, the isolation strip and its corresponding battery edge are parallel to each other, and the isolation strip forms a ring around the periphery of the battery; the width of the isolation strip is 0.02 to 0.05 mm, and the depth of the isolation strip is from the upper surface of the battery to the upper surface of the substrate. 6 . The flexible CIGS thin film battery with embedded grid electrodes according to claim 5 , characterized in that: the isolation strip is filled with insulating glue. 7 .