Back-bonded double-sided flexible gallium arsenide solar cell and preparation method thereof

Abstract

This invention discloses a back-bonded bifacial flexible gallium arsenide solar cell and its fabrication method. The flexible gallium arsenide solar cell includes an electrode system, a first cell sub-unit, a second cell sub-unit, and a bonding structure layer. The bonding structure layer is disposed between the back sides of the first and second cell sub-units, enabling integrated bonding between the back sides of the first and second cell sub-units to form a bifacial flexible gallium arsenide solar cell. The first, second, and bonding structure layers are each connected to the electrode system. This invention, through its unique back-to-back bonding structure, enables the back-bonded bifacial flexible gallium arsenide solar cell to generate electricity effectively on both sides. Under the same illumination area, its total output power is increased, significantly improving space utilization and power density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric device manufacturing, in particular to a back bonding double-sided flexible gallium arsenide solar cell and a preparation method thereof. BACKGROUND

[0002] Flexible gallium arsenide solar cells have application potential in low-altitude aircraft power supply, wearable electronic endurance, long-haul unmanned aerial vehicle power, and portable emergency energy systems due to their core advantages of high conversion efficiency, lightweight, and bendable and foldable.

[0003] Currently, traditional flexible gallium arsenide solar cells mostly adopt a single-sided structure design: the front side serves as the only effective light-receiving surface, responsible for receiving photons and completing photoelectric conversion; the back side mainly serves as an electrode preparation carrier and mechanical support, and cannot effectively utilize scattered light and reflected light incident from the back side. In practical application scenarios such as curved surface installation and multi-light source diffuse reflection, the limitation of single-sided power generation will cause a large waste of environmental light energy, directly restricting the improvement of power density per unit area or unit weight of the battery.

[0004] In the existing technical system, although a double-sided light-sensing structure is realized by constructing a double-sided PN junction on a single substrate, this scheme needs to introduce complex epitaxial growth and doping control processes, which not only greatly increases the manufacturing cost, but also increases the overall thickness of the battery and reduces its bending resistance, making it difficult to adapt to high-end application scenarios such as aerospace that require strict weight and flexibility. At the same time, if a simple mechanical stacking of two single-sided batteries is used to realize double-sided power generation, it will cause a series of problems such as doubling of the component thickness, dramatic increase in weight, and degradation of interlayer connection reliability.

[0005] Therefore, it has become a key technical problem to develop a new battery structure that can balance the high performance and lightweight core characteristics of flexible gallium arsenide batteries while realizing efficient double-sided photoelectric conversion. SUMMARY

[0006] The present application relates to the technical field of photoelectric device manufacturing, in particular to a back bonding double-sided flexible gallium arsenide solar cell and a preparation method thereof.

[0007] In order to achieve the above object, the technical scheme provided by the application is as follows: a back bonding double-sided flexible gallium arsenide solar cell, comprising an electrode system, a first cell subunit, a second cell subunit and a bonding structure layer; the bonding structure layer is arranged between the back surface of the first cell subunit and the back surface of the second cell subunit, so that the back surface of the first cell subunit is integrally bonded with the second cell subunit and forms mechanical fixation, thereby constituting a double-sided power generation flexible gallium arsenide solar cell; the first cell subunit, the second cell subunit and the bonding structure layer are respectively connected with the electrode system.

[0008] Further, the bonding structure layer is prepared by using insulating material, so that the electrical relationship of the first cell subunit and the second cell subunit is independent of each other in the case of forming mechanical connection.

[0009] Further, the insulating material is one of polyimide, BCB or silica gel.

[0010] Further, the bonding structure layer is prepared by using conductive material, so that the first cell subunit and the second cell subunit form electrical interconnection in the case of forming mechanical connection.

[0011] Further, the conductive material is metal or conductive glue.

[0012] Further, the electrode system comprises flexible conductive strips led out from the edges of the first cell subunit and the second cell subunit and conductive channels penetrating through the bonding structure layer.

[0013] A preparation method of the back bonding double-sided flexible gallium arsenide solar cell according to the above, the back surfaces of the first cell subunit and the second cell subunit are insulatively bonded, and the first cell subunit and the second cell subunit respectively form independent power generation output, and the method comprises the following steps: S1, preparing the first cell subunit and the second cell subunit; S2, spin coating a layer of BCB glue on the back surface of the first cell subunit as an insulative bonding layer; S3, aligning and adhering the back surface of the second cell subunit to the back surface of the first cell subunit coated with BCB glue; S4, heating and curing the BCB glue at a temperature of 250 DEG C in a nitrogen environment, so that the first cell subunit and the second cell subunit form firm bonding; S5, using flexible copper foil as electrode lead, and connecting to the electrode system on the respective front surfaces of the first cell subunit and the second cell subunit by ultrasonic welding.

[0014] A method for fabricating a bifacial flexible gallium arsenide solar cell based on the above-described back-bonded structure, wherein the back-side conductive bonding of the first and second cell sub-units forms a series connection for power generation output, the method comprising the following steps: S1. Prepare the first battery sub-unit and the second battery sub-unit; S2. Print conductive silver paste on the back electrode of the first battery sub-cell. S3. Align the back electrode system of the second battery sub-unit with the back electrode system of the first battery sub-unit and bond them together with conductive silver paste. S4. The conductive silver paste is cured at 150°C. At this time, the first battery sub-unit and the second battery sub-unit are connected in series through the bonding layer. S5. Lead wires from the front electrode system of the first battery cell and the front electrode system of the second battery cell.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. Doubled Power Density: Through a unique back-to-back bonding structure, the bifacial flexible gallium arsenide solar cell can generate electricity effectively on both sides. Under the same illumination area, its total output power is increased, greatly improving space utilization and power density.

[0016] 2. Compared to a single flexible gallium arsenide solar cell, the new cell structure exhibits lower warpage; 3. Compact structure, maintaining flexibility: This structure integrates two battery sub-cells into a thickness of approximately a single cell, avoiding the increase in volume and weight caused by simple physical stacking, and preserving the overall flexibility of the battery.

[0017] 4. High reliability: Mechanical fixation is achieved through bonding layers, resulting in a stable structure with excellent vibration and bending resistance, making it suitable for harsh environments.

[0018] 5. High application flexibility: The two battery cells can work independently; they can also work by connecting other batteries in series through conductive bonding to increase the output voltage and meet the needs of diverse application scenarios. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a back-bonded bifacial flexible gallium arsenide solar cell.

[0020] Figure 2 This is a process flow diagram for the fabrication of the first and second battery sub-units. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments. Example 1

[0022] See Figure 1 As shown, the back-bonded bifacial flexible gallium arsenide solar cell provided in this embodiment includes an electrode system (not shown in the figure), a first cell sub-unit 1, a second cell sub-unit 3, and a bonding structure layer 2.

[0023] A bonding structure layer 2 is disposed between the back surface 101 of the first battery sub-unit 1 and the back surface 301 of the second battery sub-unit 3, so that the back surface 101 of the first battery sub-unit 1 and the back surface 301 of the second battery sub-unit 3 are integrated and mechanically fixed to form a bifacial flexible gallium arsenide solar cell; the first battery sub-unit 1, the second battery sub-unit 3 and the bonding structure layer 2 are respectively connected to an electrode system (not shown in the figure); the electrode system (not shown in the figure) includes a flexible conductive strip extending from the edge of the first battery sub-unit and the second battery sub-unit and a conductive channel penetrating the bonding structure layer.

[0024] The bonding structure layer 2 is made of insulating material, so that the electrical relationship between the first battery sub-unit 1 and the second battery sub-unit 3 is independent when they are mechanically connected. The insulating material is one of polyimide, BCB or silicone. Example 2

[0025] The back-bonded bifacial flexible gallium arsenide solar cell provided in this embodiment differs from that in Embodiment 1 in that the bonding structure layer 2 is made of a conductive material, so that the first battery sub-unit 1 and the second battery sub-unit 3 form an electrical interconnection while forming a mechanical connection. The conductive material is metal or conductive adhesive. Example 3

[0026] The method for fabricating a back-bonded bifacial flexible gallium arsenide solar cell according to Embodiment 1 provided in this embodiment, wherein the first and second cell sub-units are back-insulatedly bonded, and the first and second cell sub-units respectively form independent power generation outputs, includes the following steps: S1, see also Figure 2 As shown, the fabrication of the first battery sub-unit and the second battery sub-unit includes the following steps: S11. Epitaxial wafer cleaning: Remove photoresist residue, oil, and particulate impurities from the surface of the epitaxial wafer.

[0027] S12, Back Gold: The back electrode system is deposited on the back side of the cleaned epitaxial wafer using an electron beam evaporation process.

[0028] S13. Electroplating or vapor deposition of bonding metals. Select the appropriate process according to the bonding strength requirements. Vapor deposition is suitable for thin and flexible applications, while electroplating is suitable for applications with high bonding reliability.

[0029] S14. After bonding the epitaxial wafer with deposited bonding metal to the temporary substrate, remove the original substrate of the epitaxial wafer.

[0030] S15, positive gold, deposit the front electrode system on the front side of the epitaxial wafer (the exposed surface after the original substrate is peeled off).

[0031] S16. Mesa etching: Mesa etching is performed on the battery edge and non-electrode areas to remove excess epitaxial material and conductive layer at the edges.

[0032] S17. Anti-reflective film deposition: An anti-reflective film is deposited on the front of the battery to reduce the reflection loss of sunlight, allowing more photons to enter the photoelectric conversion layer and improving the light absorption efficiency of the battery.

[0033] S18. Cutting the wafer: Using laser cutting technology, the epitaxial wafer after the anti-reflective coating has been deposited is precisely cut according to the preset battery size and array layout.

[0034] S19. Unloading: The cut flexible gallium arsenide battery chip is smoothly removed from the cutting stage to obtain the first battery sub-unit and the second battery sub-unit.

[0035] S2. Spin-coat a layer of BCB adhesive on the back of the first battery sub-cell as an insulating bonding layer.

[0036] S3. Align and attach the back of the second battery sub-unit with the back of the first battery unit coated with BCB adhesive.

[0037] S4. Under nitrogen atmosphere, heat and cure BCB adhesive at 250°C to form a strong bond between the first battery sub-unit and the second battery sub-unit.

[0038] S5. Flexible copper foil is used as electrode leads and is connected to the electrode systems on the front sides of the first battery sub-unit and the second battery sub-unit respectively by ultrasonic welding.

[0039] When a bifacial flexible gallium arsenide solar cell is exposed to light only on its front side, its output power is 250 mW / cm²; when both sides of the bifacial flexible gallium arsenide solar cell are exposed to the same standard light simultaneously, the total output power reaches 475 mW / cm². Example 4

[0040] The method for fabricating a back-bonded bifacial flexible gallium arsenide solar cell according to Embodiment 2 provided in this embodiment, wherein the back-side conductive bonding of the first cell sub-unit and the second cell sub-unit forms a series connection for power generation output, includes the following steps: S1, see also Figure 2 As shown, the fabrication of the first battery sub-unit and the second battery sub-unit includes the following steps: S11. Epitaxial wafer cleaning: Remove photoresist residue, oil, and particulate impurities from the surface of the epitaxial wafer.

[0041] S12, Back Gold: The back electrode system is deposited on the back side of the cleaned epitaxial wafer using an electron beam evaporation process.

[0042] S13. Electroplating or vapor deposition of bonding metals. Select the appropriate process according to the bonding strength requirements. Vapor deposition is suitable for thin and flexible applications, while electroplating is suitable for applications with high bonding reliability.

[0043] S14. After bonding the epitaxial wafer with deposited bonding metal to the temporary substrate, remove the original substrate of the epitaxial wafer.

[0044] S15, positive gold, deposit the front electrode system on the front side of the epitaxial wafer (the exposed surface after the original substrate is peeled off).

[0045] S16. Mesa etching: Mesa etching is performed on the battery edge and non-electrode areas to remove excess epitaxial material and conductive layer at the edges.

[0046] S17. Anti-reflective film deposition: An anti-reflective film is deposited on the front of the battery to reduce the reflection loss of sunlight, allowing more photons to enter the photoelectric conversion layer and improving the light absorption efficiency of the battery.

[0047] S18. Cutting the wafer: Using laser cutting technology, the epitaxial wafer after the anti-reflective coating has been deposited is precisely cut according to the preset battery size and array layout.

[0048] S19. Unloading: The cut flexible gallium arsenide battery chip is smoothly removed from the cutting stage to obtain the first battery sub-unit and the second battery sub-unit.

[0049] S2. Print conductive silver paste on the back electrode of the first battery sub-cell.

[0050] S3. Align the back electrode system of the second battery sub-unit with the back electrode system of the first battery sub-unit and bond them together with conductive silver paste.

[0051] S4. The conductive silver paste is cured at 150°C. At this time, the first battery sub-unit and the second battery sub-unit are connected in series through the bonding layer.

[0052] S5. Lead wires from the front electrode system of the first battery cell and the front electrode system of the second battery cell.

[0053] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, any changes made in accordance with the shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A back-bonded bifacial flexible gallium arsenide solar cell, characterized in that: The device includes an electrode system, a first battery sub-unit, a second battery sub-unit, and a bonding structure layer. The bonding structure layer is disposed between the back surfaces of the first battery sub-unit and the second battery sub-unit, so that the back surfaces of the first battery sub-unit and the second battery sub-unit are integrally bonded and mechanically fixed to form a bifacial flexible gallium arsenide solar cell. The first battery sub-unit, the second battery sub-unit, and the bonding structure layer are respectively connected to the electrode system.

2. The back-bonded bifacial flexible gallium arsenide solar cell according to claim 1, characterized in that: The bonding structure layer is made of insulating material, so that the electrical relationship between the first battery sub-unit and the second battery sub-unit is independent even when they are mechanically connected.

3. The back-bonded bifacial flexible gallium arsenide solar cell according to claim 2, characterized in that: The insulating material is one of polyimide, BCB, or silicone.

4. The back-bonded bifacial flexible gallium arsenide solar cell according to claim 1, characterized in that: The bonding structure layer is made of conductive material, so that the first battery sub-unit and the second battery sub-unit form an electrical interconnection while forming a mechanical connection.

5. A back-bonded bifacial flexible gallium arsenide solar cell according to claim 4, characterized in that: The conductive material is a metal or a conductive adhesive.

6. A back-bonded bifacial flexible gallium arsenide solar cell according to claim 1, characterized in that: The electrode system includes flexible conductive strips extending from the edges of the first and second battery sub-units and conductive channels penetrating the bonding structure layer.

7. A method for fabricating a back-bonded bifacial flexible gallium arsenide solar cell according to claim 1, characterized in that, The first battery sub-unit and the second battery sub-unit are back-side insulated and bonded, and the first battery sub-unit and the second battery sub-unit respectively form independent power generation outputs. The method includes the following steps: S1. Prepare the first battery sub-unit and the second battery sub-unit; S2. Spin-coat a layer of BCB adhesive on the back of the first battery sub-cell as an insulating bonding layer; S3. Align and attach the back of the second battery sub-unit with the back of the first battery unit coated with BCB adhesive. S4. Under nitrogen atmosphere, heat and cure BCB adhesive at 250°C to form a strong bond between the first battery sub-unit and the second battery sub-unit. S5. Flexible copper foil is used as electrode leads and is connected to the electrode systems on the front sides of the first battery sub-unit and the second battery sub-unit respectively by ultrasonic welding.

8. A method for fabricating a back-bonded bifacial flexible gallium arsenide solar cell according to claim 1, characterized in that, The first battery sub-unit and the second battery sub-unit are electrically bonded on their back surfaces, forming a series power generation output. The method includes the following steps: S1. Prepare the first battery sub-unit and the second battery sub-unit; S2. Print conductive silver paste on the back electrode of the first battery sub-cell. S3. Align the back electrode system of the second battery sub-unit with the back electrode system of the first battery sub-unit and bond them together with conductive silver paste. S4. The conductive silver paste is cured at 150°C. At this time, the first battery sub-unit and the second battery sub-unit are connected in series through the bonding layer. S5. Lead wires from the front electrode system of the first battery cell and the front electrode system of the second battery cell.

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