TWM519328U - Back passivated solar cell structure - Google Patents

Abstract

A PERC cell structure includes a semiconductor substrate having a front surface and a rear surface. A rear passivation layer is disposed on the rear surface. At least one local opening is formed in the rear passivation layer. A discontinuous, spot-shaped rear silver pattern is disposed on the rear passivation layer. A rear electrode pattern is formed on the rear passivation layer and fills into the local opening to form a local backside field. The discontinuous, spot-shaped rear silver pattern occupies an area that accounts for only 1.6% of the area of the rear surface.

Description

Back passivated solar cell structure

The present invention relates to the field of solar cell technology, and more particularly to a back passivated solar cell structure having higher conversion efficiency.

It is known that solar cells work by using solar radiation energy and semiconductor materials to generate electrical energy. The main materials include semiconductor materials such as single crystal germanium, polycrystalline germanium, amorphous germanium germanium or III-V compound semiconductor. Materials, etc., and conductive pastes used as electrodes, for example, silver or aluminum glue.

The solar cell manufacturing method usually performs wafer surface cleaning and roughening treatment, and then performs a diffusion process to form a phosphor glass layer and an emitter emitter region on the surface of the wafer, and then remove the phosphor glass layer by an etching process, and then An anti-reflection layer is formed, and then an electrode pattern is printed on the metal paste web on the front and back sides of the battery by screen printing, and then sintered at a high temperature to form an electrode. Finally, string welding is performed to connect the battery cells in series.

Among them, the back passivated solar cell (PERC) utilizes a passivation layer (for example, a thin aluminum oxide layer) formed on the back surface of the solar cell to reduce recombination of the electron-hole pair and can be combined with an anti-reflective coating (ARC). Reflect light back into the solar cell to increase battery efficiency.

The main purpose of this creation is to provide an improved back passivated solar cell structure that can improve conversion efficiency and reduce the amount of back silver used, thereby reducing production costs.

According to an embodiment of the present invention, the present invention provides a back passivated solar cell structure including a semiconductor substrate having a front surface and a back surface; a back passivation layer disposed on the back surface of the semiconductor substrate; at least a portion of the open area, Provided in the back passivation layer; a discontinuous, dot-shaped back silver pattern disposed on the back passivation layer; and a back electrode pattern disposed on the back passivation layer to fill the partial opening region, and A partial back surface electric field is formed in the partial opening region. The area of the discontinuous, dot-shaped back silver pattern accounts for only 1.6% of the area of the back surface.

The above described objects, features and advantages of the present invention will become more apparent from the following description. However, the following preferred embodiments and drawings are for illustrative purposes only and are not intended to limit the present invention.

Conventional PERC solar cells are often limited by the backside soldering of the module customer, and the back silver area is fixed. For example, the overall back silver area ratio is about 5.45%, so that the conversion efficiency of the PERC solar cell cannot be optimized. The applicant then proposed this creation to solve the above problems.

Please refer to FIG. 1 to FIG. 6 , which illustrate a schematic cross-sectional view of a solar cell structure produced by the present invention. As shown in FIG. 1, first, as shown in FIG. 1, a semiconductor substrate 11 such as an N-type doped crystalline germanium substrate or a crystalline germanium wafer having a thickness of, for example, about 180 to 200 μm is provided, but is not limited thereto. this.

The surface etching process and surface texture processing of the semiconductor substrate 11 are performed by a chemical etching process, and a roughened (or pyramidal) structure 101 is formed on the front surface (light receiving surface) S1 of the semiconductor substrate 11, and the semiconductor substrate is formed. The back surface S2 of 11 forms a flat surface.

As shown in Fig. 2, a surface doping region 105 and 106, for example, an N-type surface doped region, is formed on the front surface (light receiving surface) S1 and the back surface S2, respectively. The surface doped regions 105 and 106 can be formed by diffusion of a phosphorous chloride oxide (POCl ₃ ) gas using a diffusion furnace, followed by a wet etching method such as hydrofluoric acid (HF) to remove the Phosphorus glass (PSG) on the surface of the semiconductor substrate 11 (not shown).

Then, an anti-reflection layer 107, such as hafnium oxide or tantalum nitride, is formed on the front surface (light-receiving surface) S1 to cover the surface doping region 105. The anti-reflection layer 107 may be formed by techniques such as chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), plasma enhanced CVD (PECVD), and the like, but is not limited thereto.

As shown in FIG. 3, the back surface passivation layer 12 and the cap layer 13 are formed on the back surface S2 of the semiconductor substrate 11 by a chemical vapor deposition (CVD) process. For example, the back passivation layer 12 may be bismuth oxynitride (SiONx), and the cap layer 13 may be tantalum nitride (SiNx), but is not limited thereto.

For example, the back passivation layer 12 and the cap layer 13 are both dielectric materials and may be a multilayer film structure. For example, the back passivation layer 12 may be selected from the group consisting of yttrium oxide (SiOx), yttrium oxynitride (SiONx), aluminum oxide (AlOx), amorphous germanium (a-Si).

In another embodiment, the roughening (or pyramidal) structure 101 may be formed after the back passivation layer 12 and the cap layer 13 are completed.

As shown in FIG. 4, a partial opening region 103 is formed in the back surface passivation layer 12 and the cap layer 13 on the back surface S2 of the semiconductor substrate 11 by a laser process.

As shown in FIG. 5, the back contact electrode may be formed by first printing on the cap layer 13 of the back surface S2 of the semiconductor substrate 11. For example, three rows (R ₁ ) as illustrated in FIG. 6 may be printed by a silver paste screen. , discontinuous, point-like back silver pattern 18 of R ₂ , R ₃ ). It should be noted that although the three rows of back silver patterns 18 are illustrated in the drawings, they are not limited thereto. For example, in other implementations, there may be only two rows of back silver patterns 18. The dot-shaped back silver pattern 18, the area or shape of each point can be adjusted according to design requirements.

Subsequently, the front electrode pattern 17 is screen printed on the front surface S1 of the semiconductor substrate 11 with a metal paste. The above metal paste may be a silver paste, but is not limited thereto. Next, the back surface electrode pattern 19 is formed by screen printing on the back surface S2 of the semiconductor substrate 11 with a metal paste, and the back surface electrode pattern 19 is filled with the partial opening region 103. The above metal paste may be an aluminum paste, but is not limited thereto.

Finally, the front electrode pattern 17, the back contact electrode 18, and the back electrode pattern 19 are sintered by a high temperature rapid sintering furnace, and a local backside field (local BSF) 104 is formed in the partial opening region 103.

The main technical feature of the present invention is that the area of the discontinuous, dot-shaped back silver pattern 18 illustrated in Fig. 6 is only about 1.6% of the area of the back surface S2 of the semiconductor substrate 11. After electrical verification, if the above area ratio is less than 1.6%, the battery's electrical properties can no longer be further improved, and it is impossible to use the welding problem to automate the production.

The back silver pattern screen pattern used in the past prior art is not suitable for high-efficiency PERC products. The area of the back passivation layer cannot be effectively improved, and the efficiency cannot be optimized, and the consumption of the back silver compound is large, and the production cost is relatively high. high. This creation can optimize the area of the back passivation and can be mass-produced using a production welding machine. According to the experimental sentence, if the area of the back passivation layer is increased from 94.55% to 98.4% (the passivation area is increased and the partial back surface electric field area is increased), the overall conversion efficiency can be improved by about 0.2%.

The creation includes at least the following advantages: (1) The amount of back silver can be effectively reduced, thereby reducing production costs. (2) The area of the back passivation layer and the area of the partial back surface electric field (LBSF) can be effectively increased. (3) It can be compatible with the PERC process, and can increase the conversion efficiency without additional processes.

It should be noted that the above various process steps and sequences are merely illustrative, and the technical means and methods used are merely examples, and the material of each film layer is not limited to the above description.

The above descriptions are only preferred embodiments of the present invention, and all changes and modifications made by the scope of the patent application of the present invention should be covered by the present invention.

11‧‧‧Semiconductor substrate
12‧‧‧Back passivation layer
13‧‧‧ cover
17‧‧‧Front electrode pattern
18‧‧‧Back silver pattern
19‧‧‧Back electrode pattern
20‧‧‧Local passivation layer
101‧‧‧Roughened (pyramid) structure
103‧‧‧Partial opening area
104‧‧‧ Partial back electric field
105‧‧‧ surface doped area
106‧‧‧ surface doped area
107‧‧‧Anti-reflective layer
S1‧‧‧Front (glossy)
S2‧‧‧Back

1 to 6 illustrate a schematic cross-sectional view of a solar cell structure produced by the present invention, wherein FIG. 6 illustrates a top view of a discontinuous, dot-shaped back silver pattern printed on a silver paste web in FIG.

11‧‧‧Semiconductor substrate

13‧‧‧ cover

18‧‧‧Back silver pattern

S2‧‧‧Back

R ₁ , R ₂ , R ₃ ‧‧‧

Claims (10)

A back passivated solar cell structure comprising: a semiconductor substrate having a front surface and a back surface; a back passivation layer disposed on the back surface of the semiconductor substrate; at least a partial opening region disposed in the back passivation layer a discontinuous, dot-shaped back silver pattern disposed on the back passivation layer; and a back electrode pattern disposed on the back passivation layer, filling the partial opening area, and in the partial opening area A partial back surface electric field is formed. The back passivation solar cell structure of claim 1, wherein the discontinuous, dot-shaped back silver pattern has an area of only 1.6% of the area of the back surface. The back passivation solar cell structure of claim 1, wherein the discontinuous, dot-shaped back silver pattern is arranged in two rows to three rows. The back passivated solar cell structure of claim 1, wherein the front side has a roughened structure. The back passivated solar cell structure of claim 1, wherein the front side further comprises a surface doped region. The back passivation solar cell structure of claim 5, wherein the front side further comprises an anti-reflection layer disposed on the surface doped region. The back passivation solar cell structure of claim 6, wherein the front side further comprises a front electrode pattern disposed on the anti-reflective layer. The back passivation solar cell structure of claim 1, further comprising a cap layer disposed on the back passivation layer. The back passivated solar cell structure of claim 8, wherein the cap layer comprises tantalum nitride. The back passivation solar cell structure according to claim 1, wherein the back passivation layer is selected from the group consisting of cerium oxide, cerium oxynitride, aluminum oxide, and amorphous cerium.