A top electrode of a perovskite solar cell, its laser scribing method, and the perovskite solar cell

Abstract

A top electrode for a perovskite solar cell, a laser etching method thereof, and the perovskite solar cell are provided. The top electrode includes a transparent conductive oxide layer and a sacrificial layer disposed adjacent to and below the transparent conductive oxide layer. The sacrificial layer is a conductive layer with an ultraviolet light absorption rate greater than 90%. The laser etching method involves using an ultraviolet processing laser to scan the top electrode, removing the transparent conductive oxide layer and the sacrificial layer in the scanned area to complete the laser etching of the top electrode. During laser etching of the top electrode, the laser energy is preferentially absorbed by the sacrificial layer, reducing the heating of the perovskite layer, minimizing the thermal impact on both sides of the groove, avoiding edge chipping or breakage of the top electrode caused by thermal expansion of the perovskite layer, reducing the crater, and simultaneously reducing the short-circuit risk of the perovskite solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a top electrode of a perovskite solar cell, its laser scribing method, and a perovskite solar cell. Background Technology

[0002] Currently, top electrodes for perovskite solar cells are mainly divided into two categories. One category consists of metallic materials, such as gold, silver, copper, and aluminum. While these materials possess excellent conductivity, they are prone to metal ion migration during operation, which can damage the perovskite structure and affect the long-term stability of the device. The other category comprises transparent conductive oxide (TCO) thin films, such as indium tin oxide (ITO) and fluorine-doped indium tin oxide (FTO), which offer high transmittance. For transparent conductive films like ITO, their chemical stability and excellent light transmittance make them the preferred material for top electrodes in single-junction and tandem perovskite solar cells.

[0003] However, in large-area perovskite solar cell modules, laser grooving (P3 scribe lines) is required on the top electrode to achieve electrical isolation between sub-cells. Taking a perovskite cell with ITO as the top electrode as an example, due to its high transmittance (over 75%) for commonly used laser wavelengths (such as 355nm, 532nm, or 1064nm), most of the laser energy will penetrate the top electrode and be absorbed by the underlying perovskite layer, causing thermal decomposition of the perovskite layer on both sides of the grooved area, forming a large heat-affected zone. At the same time, the thermal expansion of the perovskite layer will push up the top ITO layer, causing edge chipping and shattering on both sides of the groove, forming a large "volcano" morphology. The pushed-up ITO debris may fall into the scribe lines, forming current channels, causing short circuits, and seriously affecting device performance and reliability. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention proposes a top electrode of a perovskite solar cell, a laser scribing method thereof, and a perovskite solar cell.

[0005] To achieve the above objectives, according to one aspect of the present invention, a top electrode of a perovskite solar cell is provided, further comprising a sacrificial layer disposed adjacent to a transparent conductive oxide layer below the sacrificial layer, wherein the sacrificial layer is a conductive layer with an absorption rate of more than 90% for ultraviolet light.

[0006] According to the above scheme, the transmittance of the sacrificial layer for 400-1100nm light is greater than 85%.

[0007] According to the above scheme, the sacrificial layer includes an ultrathin transition metal oxide layer.

[0008] According to the above scheme, the sacrificial layer is an AZO layer.

[0009] According to the above scheme, the Al doping concentration in the AZO layer is 1at%-3at%.

[0010] According to the above scheme, the thickness of the AZO layer is 100mm-200nm.

[0011] According to the above scheme, the transparent conductive oxide layer is an ITO layer, an FTO layer, or an IZO layer.

[0012] According to another aspect of the present invention, a laser scribing method for the top electrode of a perovskite solar cell is provided, wherein the top electrode is the aforementioned top electrode of the perovskite solar cell, and the laser scribing method includes scanning the top electrode with a processing laser, removing the transparent conductive oxide layer and the sacrificial layer in the scanning area, and completing the laser scribing of the top electrode, wherein the processing laser is an ultraviolet laser.

[0013] According to the above method, the energy density of the processing laser is 300 mJ / cm². 2 -550mJ / cm 2 .

[0014] According to the above method, the processing laser is an ultraviolet picosecond laser.

[0015] According to the above method, the frequency of the processing laser is 600kHz-2000kHz.

[0016] Following the above method, before processing laser scanning, a pre-processing laser scanning step is also included, wherein the pre-processing laser is an ultraviolet laser with an energy density of 150 mJ / cm². 2 -300mJ / cm 2 .

[0017] Using the method described above, the pre-processing laser frequency is 50kHz-200kHz.

[0018] According to the above method, the laser spot width for processing is 30µm-40µm.

[0019] According to the above method, the spot width of the pre-processing laser is 20µm-40µm.

[0020] According to another aspect of the present invention, a perovskite solar cell is provided, comprising the top electrode of the aforementioned perovskite solar cell, or comprising a perovskite solar cell obtained by a laser scribing method of the top electrode of the aforementioned perovskite solar cell.

[0021] Overall, the above-described technical solutions conceived by this invention can achieve the following beneficial effects compared with the prior art.

[0022] The perovskite solar cell top electrode and its laser scribing method of the present invention include a transparent conductive oxide layer and a sacrificial layer disposed adjacent to the transparent conductive oxide layer below it. When laser scribing is performed on the top electrode, the laser energy is preferentially absorbed by the sacrificial layer, reducing the heating of the perovskite layer, reducing the thermal impact on both sides of the groove, avoiding edge breakage and explosion of the top electrode caused by thermal expansion of the perovskite layer, reducing the crater, and reducing the short circuit risk of the perovskite solar cell. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell according to the present invention.

[0024] Figure 2 This is an optical confocal microscope image of the top electrode after laser scribing in Embodiment 1 of the present invention.

[0025] Figure 3 This is an optical confocal microscope image of the top electrode after laser scribing in Embodiment 2 of the present invention.

[0026] Figure 4 This is an optical confocal microscope image of the top electrode after laser scribing, which is a comparative example of the present invention.

[0027] Explanation of reference numerals in the attached figures: 1-top electrode, 11-transparent conductive oxide layer, 12-sacrificial layer, 2-second charge transport layer, 3-perovskite layer, 4-first charge transport layer, 5-bottom electrode, 6-substrate. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] The present invention aims to reduce the width of the heat-affected zone when laser grooving perovskite solar cells, suppress the "reverse bursting" of the perovskite layer material, and reduce the crater height.

[0030] On one hand, the top electrode of a perovskite solar cell according to the present invention, see... Figure 1This is a cross-sectional schematic diagram of a perovskite solar cell, which includes a top electrode 1. In this invention, the top electrode 1 includes a transparent conductive oxide layer 11 (TCO layer) and a sacrificial layer 12 adjacent to and disposed below the transparent conductive oxide layer 11. The sacrificial layer 12 is a conductive layer with an ultraviolet light absorption rate greater than 90%. When laser scribing is performed on the top electrode, the laser light is preferentially absorbed by the sacrificial layer, reducing the heating of the perovskite layer, mitigating the thermal impact on both sides of the groove, avoiding edge chipping or breakage of the top electrode due to thermal expansion of the perovskite layer, reducing the crater height, and simultaneously reducing the short-circuit risk of the perovskite solar cell.

[0031] Preferably, the sacrificial layer 12 has a transmittance of more than 85% for 400-1100nm light and does not affect the absorption of visible light by the perovskite layer.

[0032] Specifically, the transparent conductive oxide layer 11 can be any one of ITO (indium tin oxide), FTO (indium fluorine oxide), or IZO (indium tin oxide).

[0033] Sacrificial layer 12 is an AZO layer (aluminum-doped zinc oxide layer; Al:ZnO layer).

[0034] As a preferred technical solution, the sacrificial layer 12 of the perovskite solar cell of the present invention has an Al doping concentration of 1at%-3at%, wherein the range or point value is, for example, 1at%-1.5at%, 1.5at%-2at%, 2at%-2.5at%, 2.5at%-3at%, etc.

[0035] As a preferred technical solution, the thickness of the sacrificial layer 12 of the top electrode 1 of the perovskite solar cell of the present invention is 100nm-200nm, wherein the range or point value is, for example, 100nm, 120nm, 150nm, 180nm, 200nm, etc., and preferably 150nm.

[0036] As another alternative implementation, the sacrificial layer 12 can be an ultrathin transition metal oxide layer with a thickness of 5-10 nm, exhibiting good absorption of ultraviolet light and electrical conductivity. For example, the transition metal oxide can be MoO. x (x≈2.8–3.0), WO x (x≈2.7–3.0), V2O5, ReO x ,ReO3,NbO x / TaO x wait.

[0037] On the other hand, the present invention also provides a laser scribing method for the top electrode of a perovskite solar cell, wherein the top electrode is the top electrode 1 of the perovskite solar cell, and the scribing method includes scanning the top electrode 1 with a processing laser to remove the transparent conductive oxide layer 11 and the sacrificial layer 12 in the scanning area, thereby completing the laser scribing of the top electrode 1, wherein the processing laser is an ultraviolet laser.

[0038] When laser scribing is performed on the top electrode using the method of this invention, the heat of the laser is preferentially absorbed by the sacrificial layer, reducing the thermal impact on both sides of the scribing groove. At the same time, it avoids the "reverse explosion" caused by the thermal decomposition of the perovskite layer, reduces the crater, and reduces the width of the dead zone, achieving a good isolation effect between adjacent cells and avoiding short circuits.

[0039] In some preferred embodiments, the processing laser is an ultraviolet picosecond laser, with a preferred pulse width of less than or equal to 15 ps, for example, a preferred pulse width of 10 ps. The sacrificial layer of the present invention has a good absorption rate for ultraviolet light. Using an ultraviolet laser for processing allows the sacrificial layer to preferentially absorb the laser for etching. Ultraviolet picosecond laser processing is a cold processing method with a very small heat-affected zone; and under the action of ultra-short pulse ultraviolet photons, the material of the top electrode is directly vaporized through chemical bond energy breakage, rather than thermal ablation; resulting in neat and steep edges of the etched lines.

[0040] In some preferred embodiments, the processing laser frequency is 600kHz-2000kHz, and the scanning speed is 500mm / s-1000mm / s. Using a high-frequency laser for scanning, combined with a high spot overlap rate (>90%), allows adjacent laser spots to fully overlap in the working area. The low-energy region at the edge of the laser spot is repeatedly covered by the high-energy region of the adjacent spot, effectively compensating for uneven energy distribution and achieving a near-flat-top energy distribution, resulting in a uniform and controllable ablation effect. This embodiment results in more thorough removal of the transparent conductive oxide layer, with clean, burr-free, and residue-free groove edges. Furthermore, under high-frequency conditions, the energy required for a single pulse to achieve the same ablation effect can be significantly reduced. This significantly reduces heat diffusion and impact on the perovskite layer. The weak heat accumulation introduced by the high-frequency pulse in an extremely short time (picosecond level) helps to remove the transparent conductive oxide layer material more smoothly, reducing micro-explosions and splash contamination that may occur due to instantaneous and intense ablation.

[0041] As one implementation method, taking the transparent conductive oxide layer 11 as an ITO layer as an example, the energy density of the processing laser is set to 300 mJ / cm². 2 -550mJ / cm 2This energy density is greater than the grooving threshold of the ITO layer. When processing laser scanning grooves, the lower sacrificial layer preferentially absorbs energy and is etched, and the ITO layer will not be reverse-exploded. After the ITO layer absorbs enough energy, it changes from a solid state to a gaseous state or plasma state and is etched, which reduces the thermal impact and lowers the crater.

[0042] As another preferred embodiment, a pre-processing laser scanning step is also included before processing the laser scanning.

[0043] The energy density of the pre-processing laser is relatively low, which can be less than the opening threshold of ITO but greater than the opening threshold of AZO layer, for example, 150 mJ / cm². 2 -300mJ / cm 2 At this point, most of the laser energy is absorbed by the sacrificial layer. After absorbing the energy, the sacrificial layer expands and gently pushes up the ITO layer, causing slight damage to the ITO layer, such as the formation of some microcracks. However, this energy does not reach the ITO layer opening threshold. The plasma generated by the heating and vaporization of the sacrificial layer overflows from the cracks in the ITO film.

[0044] After pre-processing laser scanning, processing laser scanning is performed. The processing laser energy density is greater than the ITO layer opening threshold, for example, its energy density is 300 mJ / cm². 2 -400mJ / cm 2 At this energy level, the sacrificial layer continues to absorb heat and is preferentially etched, while the ITO layer is not blasted in the reverse direction. After the ITO layer absorbs enough energy, it changes from a solid state to a gaseous state or plasma state and is etched, thus reducing the thermal impact and lowering the crater height.

[0045] In some preferred embodiments, the frequency of the pre-processing laser is lower than that of the processing laser, for example, 50kHz-200kHz, and the scanning speed is 300mm / s-500mm / s.

[0046] Adding pre-processing laser scanning causes the sacrificial layer to absorb energy and expand, gently lifting the ITO film (causing slight damage and partial cracking). The plasma generated by the heated vaporization of the sacrificial layer escapes from the cracks in the ITO film in a timely manner, leaving less residue at the bottom and resulting in a smoother bottom after laser scribing. Pre-processing laser scanning at a lower energy density and low frequency and speed can achieve better processing results for the sacrificial layer.

[0047] In this invention, the width of the laser spot used for processing is 30µm-40µm, and the width of the laser spot used for pre-processing is 20-40µm, approximately the width of the groove. The groove is completed by scanning the laser spot along its length, eliminating the need for line stitching in the width direction and improving processing efficiency. This is due to the top electrode structure and laser etching method of this invention, which minimizes the heat-affected zone on both sides of the laser etching line, eliminating the need for laser reshaping or laser line stitching as required by existing technologies. It is understood that the laser spot can be rectangular, circular, or other shapes, and its width is the dimension of the spot perpendicular to the scanning direction.

[0048] See Figure 1 The perovskite solar cell includes a substrate 6, a bottom electrode 5, a first charge transport layer 4, a perovskite layer 3, a second charge transport layer 2, a sacrificial layer 12, and a transparent conductive oxide layer 11, arranged sequentially. It includes a first scribe line (P1) region, a second scribe line (P2) region, and a third scribe line (P3) region, wherein scribe line P1 penetrates the bottom electrode 5, scribe line P2 penetrates the first charge transport layer 4, the perovskite layer 3, and the second charge transport layer 2, and scribe line P3 penetrates the sacrificial layer 12 and the transparent conductive oxide layer 11. The specific positions of the first, second, and third scribe lines are as described in existing technology.

[0049] The bottom electrode 5 has a thickness of 400 nm to 600 nm. The first charge transport layer 4 is a hole transport layer with a thickness of 15 nm to 25 nm. The hole transport layer can be a layer such as nickel oxide. The perovskite layer 3 has a thickness of 400 nm to 600 nm and its chemical composition is ABX3, where A is formamidinium ion, B is lead ion and / or tin ion, and X is any one or a combination of at least two of iodide ions. For example, it can be a formamidinium lead iodide-based perovskite functional layer, whose chemical formula is usually FAPbI3 (or doped with a small amount of other ions to improve stability), and its band gap is usually between ~1.48 eV and ~1.55 eV. The effective absorption range of this type of perovskite material covers the wavelength range from the edge of ultraviolet light to near-infrared light. The main absorption band is 400 nm to 800 nm (covering violet, blue, green, yellow, orange, red light and part of the near-infrared light).

[0050] As mentioned earlier, the Al doping concentration of the sacrificial layer 12 is 1 at%-3 at%, which allows for the control of the free carrier concentration in the sacrificial layer, affecting the absorption and reflection of free carriers in the infrared region. At this doping concentration, the sacrificial layer exhibits good conductivity. Its bandgap is 3.3-3.5 eV, corresponding to an absorption edge of 350 nm-380 nm, which determines the ultraviolet absorption threshold. This allows the sacrificial layer to have a good absorption rate for ultraviolet light, which is greater than 90% in this invention. Under these conditions, combined with ultraviolet laser scanning, preferential absorption of the laser by the sacrificial layer is ensured.

[0051] As mentioned earlier, the thickness of the sacrificial layer 12 is between 100nm and 200nm. At this thickness, the sacrificial layer has a transmittance of more than 85% for visible light (400nm-1100nm) and an absorption rate of more than 90% for ultraviolet light (200nm-400nm). At this thickness, the sacrificial layer can ensure good visible light transmittance, thereby ensuring the absorption of visible light by the perovskite layer. On the other hand, the sacrificial layer has a good ultraviolet light absorption rate, which preferentially absorbs laser energy during laser etching, reduces the width of the heat-affected zone during laser grooving, suppresses the "reverse bursting" of the perovskite material, and reduces the crater height.

[0052] To enable those skilled in the art to better understand the embodiments of the present invention, the following examples are provided for description.

[0053] Example 1

[0054] In this embodiment, the perovskite solar cell includes a substrate, a bottom electrode of 400 nm FTO layer, and a hole transport layer, a perovskite layer, and an electron transport layer, all with a thickness of 400 nm. The perovskite layer is formamidinium lead iodide-based perovskite, and the electron transport layer is C 60 The top electrode consists of a 150nm thick AZO layer (sacrificial layer) and a 230nm thick ITO layer.

[0055] A 355nm ultraviolet picosecond laser was used, with a pulse width of 10ps, a frequency of 1000kHz, a spot width of 30µm, and an energy density of 450mJ / cm². 2 The laser scribing of the top electrode is completed by scanning at a speed of 800 mm / s.

[0056] Example 2

[0057] In this embodiment, the perovskite battery is the same as in Example 1.

[0058] First, a 355nm ultraviolet laser is used, with a pulse width of 10ps, a frequency of 200kHz, a spot width of 20µm, and an energy density of 150mJ / cm². 2 Pre-processing scanning will be performed at a speed of 400 mm / s.

[0059] A 355nm ultraviolet laser with a pulse width of 10ps, a frequency of 1500kHz, a spot width of 30µm, and an energy density of 350mJ / cm² is then used. 2 The laser scribing of the top electrode is completed by scanning at a speed of 1000 mm / s.

[0060] Comparative Example

[0061] In this comparative example, the perovskite solar cell differs from Example 1 only in its top electrode. The top electrode of the perovskite solar cell is a 230nm thick ITO layer without a sacrificial layer.

[0062] A 355nm ultraviolet laser was used, with a pulse width of 10ps, a frequency of 1000kHz, a spot width of 30µm, and an energy density of 450J / cm². 2 The laser scribing of the top electrode is completed by scanning at a speed of 800 mm / s.

[0063] The table below shows the laser scribing effects of the examples and comparative examples. Figure 2 This is an optical confocal microscope image of the top electrode of the perovskite solar cell in Example 1 after laser scribing. Figure 3 This is an optical confocal microscope image of the top electrode of the perovskite solar cell in Example 2 after laser scribing. Figure 4 This is an optical confocal microscope image of the top electrode of a comparative perovskite solar cell after laser scribe.

[0064] Examples / Comparative Examples Scale line width / µm Heat-affected zone width / µm Crater height / µm Edge morphology Example 1 34.113 3.885 / 2.686 0.202 Smooth and sharp Example 2 34.281 3.67 / 3.194 0.224 Smooth and sharp Comparative Example 27.47 8.192 / 6.965 3.736 The crater has a large thermal impact zone at its higher rim.

[0065] From Table 1 and Figures 2 to 4 As can be seen, using existing technologies, the laser-etched heat-affected zone (HAZ) is wide and the crater height is high. The method of this invention significantly reduces the width of the HAZ, minimizes the crater height, and produces smooth, sharp etched edges. This effectively solves the problems of crater-like protrusions and large HAZs, reducing the risk of short circuits in perovskite solar cells.

[0066] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A top electrode of a perovskite solar cell, comprising a transparent conductive oxide layer, characterized in that: It also includes a sacrificial layer disposed adjacent to the transparent conductive oxide layer below the conductive oxide layer, wherein the sacrificial layer is a conductive layer with an absorption rate of more than 90% for ultraviolet light.

2. The top electrode of a perovskite solar cell according to claim 1, characterized in that: The sacrificial layer has a light transmittance of more than 85% in the wavelength range of 400nm-1100nm.

3. The top electrode of a perovskite solar cell according to claim 1, characterized in that: The sacrificial layer comprises an ultrathin transition metal oxide layer.

4. The top electrode of the perovskite solar cell according to claim 1, characterized in that: The sacrificial layer is an AZO layer.

5. The top electrode of the perovskite solar cell according to claim 4, characterized in that: In the AZO layer, the Al doping concentration is 1 at% to 3 at%.

6. The top electrode of the perovskite solar cell according to claim 4, characterized in that: The thickness of the AZO layer is 100nm-200nm.

7. The top electrode of the perovskite solar cell according to claim 1, characterized in that: The transparent conductive oxide layer is an ITO layer, an FTO layer, or an IZO layer.

8. A laser etching method for the top electrode of a perovskite solar cell, characterized in that: The top electrode is the top electrode according to any one of claims 1 to 7. The laser scribing method includes scanning the top electrode with a processing laser, removing the transparent conductive oxide layer and the sacrificial layer in the scanning area, and completing the laser scribing of the top electrode, wherein the processing laser is an ultraviolet laser.

9. The laser etching method for the top electrode of a perovskite solar cell according to claim 8, characterized in that: The processing laser has an energy density of 300 mJ / cm 2 - 550 mJ / cm 2 .

10. The laser etching method for the top electrode of a perovskite solar cell according to claim 8, characterized in that: The processing laser is an ultraviolet picosecond laser.

11. The laser etching method for the top electrode of a perovskite solar cell according to claim 8, characterized in that: The frequency of the processing laser is 600kHz-2000kHz.

12. A laser scribing method for the top electrode of a perovskite solar cell according to claim 8, characterized in that: Before the machining laser scanning, a step of using a pre-machining laser scanning is further included, wherein the pre-machining laser is an ultraviolet laser, and the energy density of the pre-machining laser is 150 mJ / cm 2 -300 mJ / cm 2 .

13. The laser etching method for the top electrode of a perovskite solar cell according to claim 12, characterized in that: The pre-processing laser frequency is 50kHz-200kHz.

14. A laser etching method for the top electrode of a perovskite solar cell according to any one of claims 8 to 13, characterized in that: The laser spot width for processing is 30µm-40µm.

15. A laser etching method for the top electrode of a perovskite solar cell according to claim 12 or 13, characterized in that: The laser spot width for the pre-processing laser is 20µm-40µm.

16. A perovskite solar cell, characterized in that, The perovskite solar cell includes the top electrode as described in any one of claims 1 to 7, or is obtained by a laser scribing method including the top electrode of the perovskite solar cell as described in any one of claims 8 to 15.

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