A four-junction solar cell and a manufacturing method thereof

Abstract

The application discloses a four-junction solar cell and a manufacturing method thereof, and relates to the technical field of solar cells. The four-junction solar cell comprises, in the growth direction, a fourth-junction GeSi sub-cell, a third-junction GeSi sub-cell, a second-junction GaAs sub-cell, a first-junction GaInP sub-cell and an electrode contact layer arranged on a GaAs substrate in sequence; the GaAs substrate and the fourth-junction GeSi sub-cell are connected through a fourth tunnel junction; the fourth-junction GeSi sub-cell and the third-junction GeSi sub-cell are connected through a third tunnel junction; the third-junction GeSi sub-cell and the second-junction GaAs sub-cell are connected through a second tunnel junction; and the second-junction GaAs sub-cell and the first-junction GaInP sub-cell are connected through a first tunnel junction. The application can solve the problems of lattice matching and current matching of the solar cell, thereby improving the open-circuit voltage and conversion efficiency of the four-junction solar cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a four-junction solar cell and a manufacturing method thereof. BACKGROUND

[0002] Solar cells can directly convert solar energy into electricity, and are a most effective clean energy form. III-V compound semiconductor solar cells have the highest conversion efficiency in the current material system, and have good high-temperature resistance and strong anti-radiation capability, and are considered as a new generation of high-performance long-life space main power. For example, a GaInP / InGaAs / Ge lattice-matched three-junction cell has been widely used in the field of aerospace.

[0003] However, the current density of GaInP of the top cell and InGaAs of the middle cell of the traditional lattice-matched three-junction cell is much smaller than that of Ge of the bottom cell, and the solar spectrum is not fully utilized, which limits the improvement of photoelectric conversion efficiency. 0.01 The most effective way to improve the conversion efficiency of solar cells is to improve the bandgap matching degree of each sub-cell, so as to more reasonably distribute the solar spectrum.

[0004] However, at present, the matching of current of each junction is mainly realized by mismatched epitaxy and semiconductor bonding technology, but there are problems of great difficulty in epitaxial growth, poor process stability, high cost and the like. Mismatched epitaxy will cause residual stress and dislocations due to lattice mismatch of sub-cells, which affects the performance of the cell. The semiconductor bonding technology connects different bandgap sub-cells in series, and this technology has high requirements for the surface of the material, needs to have high-quality surface cleaning and passivation, and the process is complicated and the yield is very low. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provides a four-junction solar cell and a manufacturing method thereof. The bandgap combination of the four-junction solar cell according to the present application is GaInP / GaAs / GeSi / GeSi with a bandgap of 1.9 / 1.42 / 0.67 / 0.67eV, which solves the problems of lattice matching and current matching of multi-junction solar cells, thereby improving the open-circuit voltage and conversion efficiency of the four-junction solar cell.

[0006] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a four-junction solar cell, which comprises, in the growth direction, a fourth junction GeSi sub-cell, a third junction GeSi sub-cell, a second junction GaAs sub-cell, a first junction GaInP sub-cell, and an electrode contact layer, sequentially arranged on a GaAs substrate; the GaAs substrate and the fourth junction GeSi sub-cell are connected by a fourth tunnel junction; the fourth junction GeSi sub-cell and the third junction GeSi sub-cell are connected by a third tunnel junction; the third junction GeSi sub-cell and the second junction GaAs sub-cell are connected by a second tunnel junction; the second junction GaAs sub-cell and the first junction GaInP sub-cell are connected by a first tunnel junction.

[0008] The fourth junction GeSi sub-cell has a thickness of 1000-3000 nm (including the end point value) and a Si component of K, wherein 0.005≤K≤0.06; the third junction GeSi sub-cell has a thickness of 200-1000 nm (including the end point value) and a Si component of L, wherein 0.005≤L≤0.06, and the Si component of the third junction GeSi sub-cell is not less than the Si component of the fourth junction GeSi sub-cell, i.e. L≥K.

[0009] Preferably, the fourth junction GeSi sub-cell comprises, in the direction from bottom to top, a p-type GaAs back electric field, a p-type GeSi base region, an n-type GeSi emission region, and an n-type GaInP window layer; the p-type GeSi base region has a thickness of 900-2800 nm and a doping concentration of 2×10 16 -5×10 17 cm -3 , and a Si component of 0.005-0.06; the n-type GeSi emission region has a thickness of 50-150 nm and a doping concentration of 5×10 17 -5×10 18 cm -3 , and a Si component of 0.005-0.06; the above-mentioned value ranges include the end point values.

[0010] Preferably, the third junction GeSi sub-cell comprises, in the direction from bottom to top, a p-type GaAs back electric field, a p-type GeSi base region, an n-type GeSi emission region, and an n-type GaInP window layer; the p-type GeSi base region has a thickness of 100-800 nm and a doping concentration of 2×10 16 -5×10 17 cm -3 , and a Si component of 0.005-0.06; the n-type GeSi emission region has a thickness of 50-150 nm and a doping concentration of 5×10 17 -5×10 18 cm -3 , and a Si component of 0.005-0.06; the above-mentioned value ranges include the end point values.

[0011] Preferably, an n-type GaAs buffer layer is also grown on the GaAs substrate, the thickness of the GaAs buffer layer is 300-800 nm, and the doping concentration is 1 x 1018-5 x 1020cm-3. 18 -5 x 1020cm-3. 18 -3 The above-mentioned value ranges include the end values.

[0012] Preferably, the fourth tunnel junction is grown from bottom to top in order of n++-type GaAs with a doping concentration of 5 x 1018-5 x 1020cm-3and a thickness of 15-30 nm, and p++-type AlGaAs with a doping concentration of 1 x 1018-5 x 1020cm-3and a thickness of 15-30 nm. 18 -5 x 1020cm-3. 19 -3 19 -5 x 1020cm-3. 20 -3 The above-mentioned value ranges include the end values.

[0013] Preferably, the third tunnel junction is grown from bottom to top in order of n++-type GaAs with a doping concentration of 5 x 1018-5 x 1020cm-3and a thickness of 15-30 nm, and p++-type AlGaAs with a doping concentration of 1 x 1018-5 x 1020cm-3and a thickness of 15-30 nm. 18 -5 x 1020cm-3. 19 -3 19 -5 x 1020cm-3. 20 -3 The above-mentioned value ranges include the end values.

[0014] Preferably, the second tunnel junction is grown from bottom to top in order of n++-type GaAs with a doping concentration of 5 x 1018-5 x 1020cm-3and a thickness of 15-30 nm, and p++-type AlGaAs with a doping concentration of 1 x 1018-5 x 1020cm-3and a thickness of 15-30 nm. 18 -5 x 1020cm-3. 19 -3 19 -5 x 1020cm-3. 20 -3 The above-mentioned value ranges include the end values.

[0015] Preferably, the first tunnel junction is grown from bottom to top in order of n++-type GaInP with a doping concentration of 5 x 1018-5 x 1020cm-3and a thickness of 15-30 nm, and p++-type AlGaAs with a doping concentration of 1 x 1018-5 x 1020cm-3and a thickness of 15-30 nm. 18 -5 x 1020cm-3. 19 -3 19 -5 x 1020cm-3. 20 -3 The above-mentioned value ranges include the end values. ​​​​​​​​​​​​​

[0016] Preferably, the second junction GaAs sub-cell comprises, in order from bottom to top, a p-type AlGaAs back electric field, a p-type GaAs base region, an n-type GaAs emission region, and an n-type GaInP window layer; the p-type AlGaAs back electric field has a thickness of 100 nm and a doping concentration of 1x10 19 cm -3 ; the p-type GaAs base region has a thickness of 3000 nm and a doping concentration of 1x10 17 cm -3 ; the n-type GaAs emission region has a thickness of 100 nm and a doping concentration of 2x10 18 cm -3 ; and the n-type GaInP window layer has a thickness of 20 nm and a doping concentration of 2x10 18 cm -3 .

[0017] Preferably, the first junction GaInP sub-cell comprises, in order from bottom to top, a p-type AlGaInP back electric field, a p-type GaInP base region, an n-type GaInP emission region, and an n-type AlInP window layer; the p-type AlGaInP back electric field has a thickness of 50 nm and a doping concentration of 5x10 18 cm -3 ; the p-type GaInP base region has a thickness of 600 nm and a doping concentration of 5x10 17 cm -3 ; the n-type GaInP emission region has a thickness of 90 nm and a doping concentration of 2x10 18 cm -3 ; and the n-type AlInP window layer has a thickness of 20 nm and a doping concentration of 4x10 18 cm -3 .

[0018] In a second aspect, the present application also provides a method for manufacturing a four-junction solar cell, comprising the following steps:

[0019] (1) growing a fourth tunnel junction on a GaAs substrate;

[0020] (2) growing a fourth junction GeSi sub-cell on the fourth tunnel junction;

[0021] (3) growing a third tunnel junction on the fourth junction GeSi sub-cell;

[0022] (4) growing a third junction GeSi sub-cell on the third tunnel junction;

[0023] (5) growing a second tunnel junction on the third junction GeSi sub-cell;

[0024] (6) growing a second junction GaAs sub-cell on the second tunnel junction;

[0025] (7) growing a first tunnel junction on the second junction GaAs sub-cell;

[0026] (8) growing a first junction GaInP sub-cell on the first tunnel junction;

[0027] (9) growing an electrode contact layer on the first junction GaInP sub-cell.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) Compared with the traditional lattice-matched GaInP / InGaAs / Ge three-junction solar cell, the present application adds a 0.67ev sub-cell, increases the open-circuit voltage, and can increase the conversion efficiency by 9.5%.

[0030] (2) Compared with the mismatched epitaxially grown GaInP / AlInGaAs / InGaAs / Ge four-junction cell, since the present application does not exist lattice mismatch, the production process is stable, the cost is low, and the epitaxial defects are few, which improves the crystal quality of the sub-cell and can obtain higher conversion efficiency.

[0031] (3) Compared with the semiconductor bonding multi-junction cell, the semiconductor bonding needs to bond the cells obtained twice by epitaxy, which has low yield and high cost. The present application only needs to be obtained by epitaxy once, and the process is simple, which matches the existing chip production process, and the cost is much lower than that of semiconductor bonding.

[0032] (4) Compared with other solar cells made of Ge, InP substrates, the present application uses GaAs substrate with low price, which has more cost advantage. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural schematic diagram of a GaInP / GaAs / GeSi / GeSi four-junction solar cell with a bandgap combination of 1.9 / 1.42 / 0.67 / 0.67eV. DETAILED DESCRIPTION

[0034] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples, but the protection scope and implementation mode of the present application are not limited thereto.

[0035] The materials, reagents and the like used in the following examples are commercially available reagents and materials unless otherwise specified.

[0036] Example 1

[0037] This embodiment discloses a four-junction solar cell, such as Figure 1As shown, the fourth junction GeSi sub-cell, the third junction GeSi sub-cell, the second junction GaAs sub-cell, the first junction GaInP sub-cell and the electrode contact layer are sequentially arranged on the GaAs substrate in the growth direction; the GaAs substrate and the fourth junction GeSi sub-cell are connected through the fourth tunnel junction; the fourth junction GeSi sub-cell and the third junction GeSi sub-cell are connected through the third tunnel junction; the third junction GeSi sub-cell and the second junction GaAs sub-cell are connected through the second tunnel junction; and the second junction GaAs sub-cell and the first junction GaInP sub-cell are connected through the first tunnel junction.

[0038] The solar cell is a four-junction solar cell with a 1.9 / 1.42 / 0.67 / 0.67 eV band gap combination, which is made of a 4-inch n-type GaAs substrate by using a metal organic chemical vapor phase epitaxy deposition technology (MOCVD).

[0039] The embodiment also discloses a manufacturing method of the four-junction solar cell.

[0040] (1) growing an n-type GaAs buffer layer on the GaAs substrate, wherein the thickness of the GaAs buffer layer is 500 nm, and the doping concentration is 1×10 18 cm -3 .

[0041] (2) growing the fourth tunnel junction: growing, from bottom to top, n++ type GaAs with a doping concentration of 5×10 19 cm -3 and a thickness of 20 nm, and p++ type AlGaAs with a doping concentration of 1×10 20 cm -3 and a thickness of 20 nm, to form the fourth junction tunnel junction.

[0042] (3) growing the fourth junction GeSi sub-cell: the fourth junction GeSi sub-cell sequentially comprises, from bottom to top, a p-type GaAs back electric field, a p-type GeSi base region, an n-type GeSi emitter region and an n-type GaInP window layer; the p-type GaAs back electric field has a thickness of 50 nm and a doping concentration of 1×10 20 cm -3 ; the p-type GeSi base region has a thickness of 2000 nm, a doping concentration of 1×10 17 cm -3 and a Si component of 0.02; the n-type Ge 0.98 Si 0.02 emitter region has a thickness of 100 nm, a doping concentration of 2×10 18 cm -3 and a Si component of 0.02; and the n-type GaInP window layer has a thickness of 20 nm and a doping concentration of 2×10 18 cm-3 .

[0043] (4) Growth of the third tunnel junction: the third tunnel junction is grown from bottom to top with n++ GaAs with a doping concentration of 5 x 1018 cm-3 and a thickness of 20 nm and p++ AlGaAs with a doping concentration of 1 x 1018 cm-3 and a thickness of 20 nm, i.e. the third tunnel junction is formed. 19 cm -3 20 cm -3

[0044] (5) Growth of the third junction GeSi sub-cell: the third junction GeSi sub-cell comprises from bottom to top p-type GaAs back field with a thickness of 50 nm and a doping concentration of 1 x 1018 cm-3, p-type GeSi base region with a thickness of 700 nm and a doping concentration of 1 x 1018 cm-3, Si composition of 0.02, n-type GeSi emitter region with a thickness of 100 nm and a doping concentration of 2 x 1018 cm-3, Si composition of 0.02, and n-type GaInP window layer with a thickness of 20 nm and a doping concentration of 2 x 1018 cm-3. 20 cm -3 17 cm -3 18 cm -3 18 cm -3 .

[0045] (6) Growth of the second tunnel junction: the second tunnel junction is grown from bottom to top with n++ GaAs with a doping concentration of 5 x 1018 cm-3 and a thickness of 20 nm and p++ AlGaAs with a doping concentration of 1 x 1018 cm-3 and a thickness of 20 nm, i.e. the second tunnel junction is formed. 19 cm -3 20 cm -3

[0046] (7) Growth of the second junction GaAs sub-cell: the second junction GaAs sub-cell comprises from bottom to top p-type AlGaAs back field with a thickness of 100 nm and a doping concentration of 1 x 1018 cm-3, p-type GaAs base region with a thickness of 3000 nm and a doping concentration of 1 x 1018 cm-3, n-type GaAs emitter region with a thickness of 100 nm and a doping concentration of 2 x 1018 cm-3, and n-type GaInP window layer. 19 cm -3 17 cm -3 18 cm -3 ​​​​​​​​​The n-type GaInP window layer has a thickness of 20 nm and a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

[0047] (8) Growth of the first tunnel junction: The first tunnel junction is grown sequentially from bottom to top with a doping concentration of 5×10⁻⁶. 19 cm -3 n++ type GaInP with a thickness of 20 nm and a doping concentration of 1×10 20 cm -3 A 20nm thick p++ type AlGaAs layer is formed, which constitutes the first tunnel junction;

[0048] (9) Growth of the first junction GaInP sub-cell: The first junction GaInP sub-cell, from bottom to top, comprises a p-type AlGaInP back electric field, a p-type GaInP base region, an n-type GaInP emitter region, and an n-type AlInP window layer; the p-type AlGaInP back electric field has a thickness of 50 nm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The p-type GaInP base region has a thickness of 600 nm and a doping concentration of 5 × 10⁻⁶. 17 cm -3 The n-type GaInP emitter region has a thickness of 90 nm and a doping concentration of 2 × 10⁻⁶. 18 cm -3 The n-type AlInP window layer has a thickness of 20 nm and a doping concentration of 4 × 10⁻⁶. 18 cm -3 .

[0049] (10) Final growth of the n-type GaAs electrode contact layer: The thickness of the n-type GaAs electrode contact layer is 500 nm, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 .

[0050] The quadruple-junction solar cell fabricated by this invention can solve the lattice matching and current matching problems of multi-junction solar cells, thereby improving the open-circuit voltage and conversion efficiency of quadruple-junction solar cells.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A four-junction solar cell, characterized in that, A fourth junction GeSi sub-cell, a third junction GeSi sub-cell, a second junction GaAs sub-cell, a first junction GaInP sub-cell, and an electrode contact layer are sequentially disposed on a GaAs substrate according to the growth direction. The GaAs substrate and the fourth junction GeSi sub-cell are connected through a fourth tunnel junction. The fourth junction GeSi sub-cell and the third junction GeSi sub-cell are connected through a third tunnel junction. The third junction GeSi sub-cell and the second junction GaAs sub-cell are connected through a second tunnel junction. The second junction GaAs sub-cell and the first junction GaInP sub-cell are connected through a first tunnel junction. The thickness of the fourth junction GeSi sub-cell is 1000-3000 nm; the thickness of the third junction GeSi sub-cell is 200-1000 nm. The fourth junction GeSi sub-cell and the third junction GeSi sub-cell, from bottom to top, sequentially include a p-type GaAs back electric field, a p-type GeSi base region, an n-type GeSi emitter region, and an n-type GaInP window layer. The p-type GeSi base region in the fourth junction GeSi sub-cell has a thickness of 900-2800 nm and a doping concentration of 2 × 10⁻⁶. 16 -5×10 17 cm -3 The n-type GeSi emitter region has a thickness of 50-150 nm and a doping concentration of 5 × 10⁻⁶. 17 -5×10 18 cm -3 The Si composition of the emitter and base regions is 0.02; the thickness of the p-type GeSi base region in the third junction GeSi sub-cell is 100-800 nm, and the doping concentration is 2 × 10⁻⁶. 16 -5×10 17 cm -3 The n-type GeSi emitter region has a thickness of 50-150 nm and a doping concentration of 5 × 10⁻⁶. 17 -5×10 18 cm -3 The Si composition of the emitter and base regions is 0.

02.

2. The four-junction solar cell as described in claim 1, characterized in that, An n-type GaAs buffer layer is also grown on the GaAs substrate. The thickness of the GaAs buffer layer is 300-800 nm, and the doping concentration is 1×10⁻⁶. 18 -5×10 18 cm -3 .

3. The quad-junction solar cell as described in claim 1, characterized in that, The fourth, third, second, and first tunnel junctions are all grown sequentially from bottom to top with a doping concentration of 5×10⁻⁶. 18 -5×10 19 cm -3 n++ type GaAs with a thickness of 15-30 nm and a doping concentration of 1×10 19 -5×10 20 cm -3 p++ type AlGaAs with a thickness of 15-30nm.

4. The four-junction solar cell as described in claim 1, characterized in that, The second GaAs sub-cell, from bottom to top, includes a p-type AlGaAs back electric field, a p-type GaAs base region, an n-type GaAs emitter region, and an n-type GaInP window layer.

5. The four-junction solar cell as described in claim 1, characterized in that, The first GaInP sub-cell, from bottom to top, comprises a p-type AlGaInP back electric field, a p-type GaInP base region, an n-type GaInP emitter region, and an n-type AlInP window layer.

6. The method for manufacturing a four-junction solar cell according to any one of claims 1-5, characterized in that, Includes the following steps: (1) A fourth tunnel junction is grown on a GaAs substrate; (2) A fourth junction GeSi subcell is grown on the fourth tunnel junction; (3) A third tunnel junction is grown on the fourth junction GeSi subcell; (4) A third junction GeSi subcell is grown on the third tunnel junction; (5) A second tunnel junction is grown on the third junction GeSi subcell; (6) Grow a second junction GaAs subcell on the second tunnel junction; (7) A first tunnel junction is grown on the second junction GaAs subcell; (8) Grow a first junction GaInP subcell on the first tunnel junction; (9) An electrode contact layer is grown on the first junction GaInP subcell.

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