CN105140321B - Flexible CIGS solar cell and metal substrate preparation method thereof - Google Patents

Abstract

The invention provides a flexible CIGS solar cell which is high in solar energy absorption rate and conversion rate. The flexible CIGS solar cell comprises a flexible metal substrate, and is characterized in that the metal substrate is provided penetrating holes whose inner wall are bowl-shaped, each hole is internally provided with a transparent bead, and the upper end and the lower end of each transparent bead protrude out of the metal substrate respectively; a bead lower electrode layer, a CIGS absorption and conversion layer, a buffer layer and an upper electrode layer are sequentially arranged at the surface of transparent bead protruding out of the upper surface of the metal substrate from the inside out; and the lower surface of the metal substrate is provided with an insulating layer, and the insulating layer is provided with a lower electrode layer connected with the bead body lower electrode layer. The invention further provides a flexible metal substrate preparation method which is high in efficiency and good in repeatability. The preparation method comprises the steps of cleaning, photosensitive adhesive coating, solidifying, double-side exposing, developing, hardening, double-side etching, adhesive stripping and the like. A Fe2Cl3 solution is adopted to act as an etching agent to carrying out etching on both sides of the metal substrate, and injection pressures of the etching agent at two sides are 2-4bar and 1-3.5bar respectively, thereby forming the bowl-shaped penetrating holes with one big opening at one side and one small opening at the other side.

Description

Flexible CIGS solar cell and its metal substrate preparation method

technical field

The technology of the invention relates to a flexible CIGS solar cell and a method for preparing a flexible metal substrate.

Background technique

Copper indium gallium selenium thin film solar cells have the characteristics of low production cost, less pollution, no fading, and good weak light performance. It is called "a very promising new thin-film solar cell in the next era" internationally. In addition, the battery is soft, uniform, and has a certain hardness and strength, and is suitable for application on uneven surfaces, such as irregular curtain walls of large buildings, car roofs, etc., and has a large market.

However, the existing copper indium gallium selenide thin-film solar cells are flat plates with a stacked structure, and the absorption rate and conversion rate of solar energy are still low.

Contents of the invention

The purpose of the present invention is to provide a flexible CIGS solar cell with high solar energy absorption rate and conversion rate.

The flexible CIGS solar cell of the present invention comprises a flexible metal base; there are through holes on the metal base, the holes on the upper surface side of the metal base are large, the holes on the lower surface side of the metal base are small, and the inner wall of the hole is bowl-shaped; transparent beads The body is located in the hole, and the upper and lower ends of the transparent beads respectively protrude from the upper and lower surfaces of the metal base; on the surface of the transparent beads opposite to the inner wall of the cavity and on the surface of the transparent beads protruding from the upper surface of the metal base, From the inside to the outside, there are bead lower electrode layer, copper indium gallium selenide absorption conversion layer, buffer layer; there is an upper electrode layer on the upper surface of the metal substrate and the buffer layer protruding from the upper surface of the metal substrate; on the lower surface of the metal substrate An insulating layer is provided, and a lower electrode layer is arranged on the insulating layer, and the lower electrode layer communicates with the lower electrode layer of the beads.

Beneficial effects of the present invention: the working principle of the flexible CIGS solar cell is that light is irradiated on the copper indium gallium selenium absorption conversion layer through the upper electrode layer, and the light energy is directly converted into electrical energy through the photochemical effect of the absorption conversion layer. A current is formed between the electrode layers. Compared with the planar CIGS solar cell, since the present invention adopts the bead structure, the light-receiving area per unit area is increased, the volume of the absorbing layer is increased, the material absorption rate is improved, the absorption coefficient is as high as 10 ⁵ /cm, and the cell conversion efficiency can reach More than 20%. If the thickness of the upper electrode layer is too thick, the light transmittance will be affected and the light conversion efficiency will be reduced. If the thickness of the upper electrode layer is too thin, the increase of resistance will affect the output current. Because the present invention uses conductive metal as the connecting body of the bead body, it is connected with the upper electrode layer, so although the thickness of the upper electrode layer is reduced, the resistance of the upper electrode layer is reduced due to the effect of the metal conductor, which is conducive to the improvement of light transmittance and the improvement of conversion efficiency.

In the above flexible CIGS solar cell, the metal substrate is a stainless steel substrate with a thickness of 20-500um; the thickness of the upper electrode layer is 10-180um. The metal substrate is a metal that has electrical conductivity and is not rusted due to environmental influences, such as a stainless steel substrate. The thickness of the substrate is small, the effective area of the hole wall is small, the contact area with the beads is small, the force of adhering to the beads is small, and the beads are easy to fall off. If the substrate thickness is too thick, it is difficult to process cavitation corrosion, and a larger bead body is required. The larger the bead body, the greater the weight, and the higher the unevenness difference, and it is easy to be affected by external force and fall off during use. A stainless steel substrate with a thickness of 20-500um is preferably used.

In the above flexible CIGS solar cell, the lower electrode layer and the bead lower electrode layer are both molybdenum electrode layers.

In the flexible CIGS solar cell mentioned above, the upper electrode layer is a transparent conductive layer of ZnO.

In the above-mentioned flexible CIGS solar cell, the lower electrode layer of the beads, the copper indium gallium selenium absorption conversion layer, the buffer layer, and the upper electrode layer on the buffer layer protruding from the upper surface of the metal substrate are all in the shape of a spherical crown; two adjacent holes The distance between them is equal to the outer diameter of the spherical cap-shaped upper electrode layer protruding from the buffer layer on the upper surface of the metal base.

In the flexible CIGS solar cell mentioned above, the buffer layer is ZnS. The buffer layer is a transition between the low-bandgap CIGS absorption conversion layer and the high-bandgap ZnO window layer, which reduces the lattice mismatch and band gap imbalance between the two band gaps, and prevents CIGS absorption conversion when sputtering the ZnO window layer. Layer damage, etc., played an important role in improving the efficiency of CIGS thin film solar cells.

The invention also provides a method for preparing a flexible metal substrate in a flexible CIGS solar cell with high efficiency, good repeatability, and better hole bowl-shaped inner walls.

According to the preparation method of the flexible metal substrate in the flexible CIGS solar cell of the present invention, the metal substrate has through holes, the holes on the upper surface side of the metal substrate are large, the holes on the lower surface side of the metal substrate are small, and the holes are The inner wall is bowl-shaped; the preparation method of the metal base comprises the following steps:

a. Clean the flexible metal substrate to remove surface oil and impurities;

b. Apply water-soluble photosensitive glue on both sides of the flexible metal substrate, and control the thickness of the film to 4-10um; dry and cure the coated photosensitive glue;

c. Use two photomasks with mask patterns on both sides of the flexible metal substrate; irradiate the photosensitive glue on both sides of the flexible metal substrate with ultraviolet light to form the same latent pattern as the mask pattern, and the ultraviolet light intensity is 250 -1000mw/cm ² , exposure time 20-120s;

d. Use pure water with a certain temperature as the developer, and flow through the photosensitive adhesive on both sides of the metal substrate in the form of water flow. After passing through the water bath, the photosensitive adhesive that has not been exposed to ultraviolet light is dissolved by water, and the photosensitive adhesive that is exposed to ultraviolet light remains. The latent pattern formed by the photosensitive adhesive on both sides of the metal substrate is revealed, exposing the metal surface to be etched;

e. Rinse the remaining part of the photosensitive glue with a chromic acid flow solution with a concentration of 10-30% and a temperature of 30-70 ° C. Within 2 minutes, the remaining part of the photosensitive glue will be polymerized, and then pass through 180-220 ° C for 6 minutes. Infrared drying within, so that the remaining part of the photosensitive adhesive forms a protective layer;

f. Use Fe ₂ Cl ₃ solution with a density of 1.2-1.8g/ml and a temperature of 50-80°C as a metal etchant to etch both sides of the metal substrate at the same time, and the etching time is within 60 minutes; the injection pressure of the metal etchant on the large hole side is 2 -4bar, injection pressure of metal etchant on the small hole side is 1-3.5bar; the metal in the place where there is no protective layer is eroded by the Fe ₂ Cl ₃ etching solution, and under the action of the etching solution, a through hole with a large hole on one side and a small hole on the other side is formed. At the same time, under the action of lateral etching, the inner wall of the hole is shaped like a bowl;

g. Peel off the photosensitive adhesive as a protective layer, so that the metal surface is completely exposed.

In the above-mentioned method for preparing the metal substrate, in step g, the lye with a concentration of not higher than 20%, a temperature of 75-95°C, and a pressure of 1-3 bar is used to peel off and rinse off the photosensitive adhesive left on the metal surface as a protective layer , so that the metal surface is completely exposed. The lye is sodium hydroxide or potassium hydroxide. If the concentration of lye is too high, it will corrode the metal surface, and the peeling effect of the photosensitive adhesive is poor and the peeling speed is slow at low temperature and low pressure. Too much pressure can easily cause deformation of the metal film.

The preparation method of the above-mentioned metal substrate has after step g:

Step h: cleaning, using pure water with a pressure of 1-3 bar to clean the metal substrate after stripping the photosensitive adhesive to remove surface impurities;

Step i: drying, using a vacuum to remove moisture from the surface of the metal substrate, and drying the moisture remaining on the metal substrate by baking at 180-200°C.

In the above-mentioned method for preparing the metal substrate, the metal substrate wound into a coil is unrolled, and after going through the steps described in claim 1 in sequence, it is then rewound. Under normal circumstances, the unwinding speed does not exceed 2m/min, and can be adjusted and controlled. Preferably, the viscosity of the water-soluble photosensitive adhesive in step b is 6-9 cp. After testing, when the unwinding speed is 2m/min, when the viscosity of the water-soluble photosensitive adhesive is 6-9cp, the natural flowing speed is uniform, and the thickness of the photosensitive adhesive formed on the surface of the metal substrate meets the requirements. Otherwise, the formed film is either too thick or too thin. If the film is too thick, it is not conducive to etching (etching is difficult). If the film is too thin, the protective film formed by photolithography is easy to fall off during corrosion, which is not conducive to forming a protective effect in etching.

Beneficial effects of the present invention: the manufacturing method adopts steps such as cleaning, coating of photosensitive adhesive, curing, double-sided exposure, development, film hardening, double-sided etching, and stripping, and can be prepared on the metal substrate used in solar cells. The holes are regularly arranged and uniform in size, and the inner wall of the holes is bowl-shaped and arc-shaped. Double-sided mask exposure, double-sided etching, and double-sided etching rate are controllable, so as to obtain better etching depth and inner wall shape, and the manufacturing method is efficient and repeatable. The unwinding speed does not exceed 2m/min. When the ultraviolet light intensity is lower than 250 mw/cm ² and the exposure time is less than 20s, it is easy to cause underexposure, the photocuring effect of the photosensitive adhesive is reduced, and the film is easy to fall off during development or etching; When the intensity is higher than 1000mw/cm ^{2 and the} exposure time is greater than 120s, it is easy to cause overexposure, so that the photosensitive adhesive in the position that should not be cured is also cured by light, which reduces the resolution of the graphics and the accuracy of the position; the density of the Fe ₂ Cl ₃ etchant When the temperature exceeds 1.2-1.8g/ml and the temperature exceeds 50-80°C, it will have an accurate impact on the corrosion of the metal substrate, either more corrosion or less corrosion; according to the ratio of the etching amount of the large and small holes, the metal etchant on the side of the large hole The ratio of injection pressure to injection pressure on the small hole side is generally 1:0.7.

Description of drawings

Figure 1 is a schematic diagram of the structure of a flexible CIGS solar cell;

Fig. 2 is a schematic diagram of a flexible metal substrate;

Fig. 3 is the top view of Fig. 2;

Fig. 4 is a flow chart of the preparation of a flexible metal substrate;

FIG. 5 is a schematic diagram of a double-sided etching process.

detailed description

Referring to the flexible CIGS solar cell shown in Figure 1, it has a stainless steel metal base 1 with a thickness of 200um and a width of 720mm; see Figures 2 and 3, there are through holes 11 on the metal base 1, and the holes 11 are on the side of the upper surface 14 of the metal base The formed large hole 12 and the small hole 13 on the lower surface 15 side. The shape of the inner wall of the hole is bowl-shaped (also called a spherical crown shape), which is just used for placing the transparent bead 2 . The surface of the transparent bead is plated with a lower electrode layer (molybdenum) 3 , a copper indium gallium selenium absorption conversion layer 4 , and a ZnS buffer layer 5 sequentially from the inside to the outside. Then magnetron sputtering is used to deposit an upper electrode layer (transparent conductive layer ZnO) 6 on the upper surface of the metal substrate and on the buffer layer protruding from the upper surface of the metal substrate, and the thickness of the upper electrode layer is 100 um. An insulating layer 7 and a lower electrode layer (molybdenum) 8 are sequentially coated on the lower surface of the metal base. The lower electrode layer 8 communicates with the bead lower electrode layer 3 .

The lower electrode layer of the bead body, the copper indium gallium selenide absorption conversion layer, the buffer layer, and the upper electrode layer of the bead body (that is, the upper electrode layer on the buffer layer protruding from the upper surface of the metal substrate) are all in the shape of a spherical cap. The shape of the hole on the flexible metal substrate is just enough to put the transparent beads in, so as to ensure that the inner wall of the hole is similar to the shape of the surface of the beads (including the coating), and the two surfaces coincide when the beads are put in. There are multiple rows of holes on the flexible metal base, two adjacent rows of holes are arranged in a staggered manner, and the distance between two adjacent holes in the same row is equal to the outer diameter of the electrode layer on the bead body. The hole distribution rules arrange all the beads and the electrode layer on the beads with the maximum density to obtain the maximum light effect.

The raw material for the flexible metal substrate is metal substrate tape. The flexible metal substrate adopts the preparation method of double-sided pattern simultaneous exposure, double-sided simultaneous etching, and double-sided etching rate control. The basic preparation process is shown in Figure 4, which mainly includes: unwinding, cleaning, coating photosensitive adhesive, curing, Double-sided exposure, development, film hardening, double-sided etching, stripping, cleaning, drying, and winding.

For unwinding, place the flexible metal base tape on the storage table for unwinding, and the running speed of the metal base is 0.6m/min;

Cleaning, using P3 cleaning agent with a concentration of 1-20‰ (for example, 1.6‰), at a temperature of 75-95°C (for example, 95°C) and a spray pressure of 1.5-3.5bar (for example, 2.6bar) on the surface of the metal substrate Roll brush cleaning for 6 minutes. Then rinse the metal substrate with deionized water for 2 minutes to remove oil and impurities on the surface of the metal substrate.

Apply glue, rinse both sides of the metal substrate with deionized water with a pH value of 6.8, and rinse with acidic deionized water to neutralize the alkaline residue that may remain after the previous cleaning step. Then apply water-soluble photosensitive glue on both sides of the flexible metal substrate. The viscosity of the water-soluble photosensitive glue at 40°C is 7.5cp, and the film thickness is 7um;

Curing, use the infrared method to dry and cure the photosensitive adhesive coated on both sides of the metal substrate, the surface temperature is 60°C, and the drying time is 42 minutes;

For exposure, use two photomask plates with mask patterns, place them on both sides of the flexible metal substrate, and use an alignment device to align the two mask patterns. Irradiate the photosensitive adhesive on both sides of the flexible metal substrate with ultraviolet light to form the same latent pattern as the mask pattern, with an exposure intensity of 420mw/cm ² and an exposure time of 30s;

For development, use deionized water at a temperature of 70°C as a developer, and flow through the photosensitive glue on both sides of the metal substrate in the form of water flow, and dissolve the photosensitive glue that has not been exposed to ultraviolet light through a water bath, and retain the photosensitive glue that has not been exposed to ultraviolet light. Let the latent pattern formed by the photosensitive adhesive on both sides of the flexible metal substrate be revealed, so that the metal surface that needs to be etched is exposed;

To harden the film, rinse the remaining part of the photosensitive adhesive with a 13.5% chromic acid solution at a temperature of 40°C for 0.5 minutes to polymerize the remaining part of the photosensitive adhesive, and pass it through an infrared oven at 210°C for 4 minutes to harden the film , the photosensitive adhesive on the upper and lower surfaces of the metal substrate is retained to form a firm protective layer 9, 10; the protective layer 9 has a large hole 91 corresponding to the large hole 12 on the upper surface of the metal substrate 14, and the protective layer 10 has a The small hole 101 corresponding to the small hole 13 on one side of the surface 15 .

For etching, use a Fe2Cl3 solution with a specific gravity of 1.462g/ml and a temperature of 60°C. The injection pressure on the side of the large hole 91 is 4 bar, and the injection pressure on the side of the small hole 101 is 2.5 bar. Etch both sides of the metal substrate at the same time, and the etching time is 50 minutes. Referring to Figure 5, due to the effect of the surface protective layer, the metal in the place with the protective layer is preserved, and the metal in the place without the protective layer is eroded by the Fe2Cl3 etching solution; due to the different injection pressure of the etching solution on the side of the large and small holes, and the different sizes of the large and small holes, Under the action of the etching solution, a through hole with a large hole on one side and a small hole on the other side is formed on the metal substrate, and at the same time, the shape of the cavity is shaped like a bowl under the action of lateral etching.

For peeling, use lye with a concentration of 4%, a temperature of 85°C, and a pressure of 1.4 bar to peel off and rinse off the photosensitive adhesive left on the metal surface as a protective layer, so that the metal surface is completely exposed;

Cleaning, using pure water with a pressure of 1 bar to clean the metal substrate after stripping the photosensitive adhesive to remove surface impurities;

Drying, use vacuum to remove the moisture on the surface of the metal substrate, and dry the moisture left on the metal substrate after baking at 180-200°C for 3 minutes;

Winding, the dried metal substrate is wound up by a winding device.

The beneficial effect of preparation method of the present invention:

Due to the erosion effect of etching, the double-sided etching rate control is adopted, and the shape of the hole matches the shape of the transparent bead;

Adopt double-sided simultaneous exposure and double-sided simultaneous etching, which is fast and efficient, and it is difficult to achieve the same effect by other methods;

Sustainable and continuous production, high repeatability of exposure and etching processes, good product size consistency, and high product quality rate.

Claims (10)

1. flexible cigs solaode, is characterized in that: it includes flexible metal basement；The hole running through is had on metallic substrates, The hole of surface side is big on the metallic substrate, and the hole of metallic substrates lower surface side is little, and hole inwall becomes bowl-type；Transparent bead position In hole, and the upper and lower side of transparent bead protrudes from the upper and lower surface of metallic matrix respectively；Relative with hole inwall On Transparent bead body surface face and on the Transparent bead body surface face protruding from metallic substrates upper surface, have successively from the inside to the outside under bead Electrode layer, CIGS absorb conversion layer, cushion；On the metallic substrate on surface and protrude from the slow of metallic substrates upper surface Rush and upper electrode layer is had on layer；Insulating barrier is had on metallic substrates lower surface, insulating barrier has lower electrode layer, lower electrode layer and bead Lower electrode layer communicates.

2. flexibility cigs solaode as claimed in claim 1, is characterized in that: described metallic substrates are stainless steel base, Thickness 20-500um；The thickness of upper electrode layer is 10-180um.

3. flexibility cigs solaode as claimed in claim 1, is characterized in that: described lower electrode layer and bead lower electrode layer It is molybdenum electrode layer.

4. flexibility cigs solaode as claimed in claim 1, is characterized in that: upper electrode layer is transparency conducting layer zno.

5. flexibility cigs solaode as claimed in claim 1, is characterized in that: bead lower electrode layer, CIGS absorb Conversion layer, cushion, the upper electrode layer protruding from the cushion of metallic substrates upper surface are spherical；Two neighboring hole Between spacing be equal to the external diameter protruding from spherical upper electrode layer on the cushion of metallic substrates upper surface.

6. the preparation method of the flexible metal basement in flexible cigs solaode, described metallic substrates have the hole run through Hole, the hole of surface side is big on the metallic substrate, and the hole of metallic substrates lower surface side is little, and hole inwall becomes bowl-type；Its feature It is: the preparation method of this metallic substrates comprises the steps:

A, cleaning flexible metal basement, remove surface and oil contaminant, impurity；

B, flexible metal basement both sides apply water soluble photosensitive, film thickness control 4-10um；The photoresists of coating are done Dry solidification；

C, it is placed on flexible metal basement both sides using two pieces of photomask blank with mask pattern；With the flexible gold of ultraviolet light The photoresists belonging to substrate both side surface form latent pattern, ultraviolet ray intensity 250-1000mw/cm with mask plate pattern identical²、 Time of exposure 20-120s；

D, it is used the pure water with uniform temperature as developing agent, metallic substrates both side surface photoresists are flowed through with water flow mode, To be dissolved in water without uv-exposure part photoresists through water-bath, uv-exposure part photoresists remain, allow flexible golden The latent pattern belonging to the formation of substrate both side surface photoresists is manifested so that the metal surface of needs etching is exposed out；

E, the photoresists concentration to member-retaining portion are 10-30%, the chromic acid stream water solution of temperature 30-70 DEG C rinses, the time Within 2min, make the photoresists of member-retaining portion that polymerization to occur, then by the infrared drying within 180-220 DEG C, 6min, make The photoresists of member-retaining portion form protective layer；

F, using density be 1.2-1.8g/ml, the fe of temperature 50-80 DEG C₂cl₃Solution is double to metallic substrates as metal etchants Face is etched simultaneously, within etching period 60min；Macropore side metal etchants injection pressure 2-4bar, the erosion of aperture side metal Carve agent injection pressure 1-3.5bar；The local metal of unprotected layer is by fe₂cl₃Etching solution eats away, shape under etching liquid effect Become lateral opening big, lateral opening little perforated holes, make hole inner wall shape such as bowl-type under lateral etches effect simultaneously；

G, the photoresists as protective layer are peeled off, make metal surface completely exposed out.

7. the preparation method of metallic substrates as claimed in claim 6, is characterized in that:

In step g, concentration is not higher than 20%, temperature 75-95 DEG C, the alkali liquor of pressure 1-3bar, will be retained in metal surface Photoresists as protective layer are peeled off, are rinsed out, and make metal surface completely exposed out.

8. the preparation method of the metallic substrates stated as claim 7, is characterized in that:

Have after step g:

Step h: cleaning, the pure water using 1-3 bar pressure is carried out to the metallic substrates peeled off after photoresists, removes surface Impurity；

Step i: be dried, using vacuum by metal substrate surface moisture removal, metal will be retained in through 180-200 DEG C of baking Suprabasil moisture content is dried.

9. the preparation method of metallic substrates as claimed in claim 6, is characterized in that: the metallic substrates being wound into coiled material are put Volume, after sequentially passing through each step of preparation method described in claim 6, then winds.

10. the preparation method of metallic substrates as claimed in claim 9, is characterized in that: water soluble photosensitive described in step b Viscosity number 6-9cp.