CN111816727A - An Interdigitated Back Contact Heterojunction Solar Cell Based on High Efficiency Doped Amorphous Silicon Technology Based on LPCVD - Google Patents

Abstract

The invention provides an interdigital back contact heterojunction solar cell based on an LPCVD (low pressure chemical vapor deposition) high-efficiency doped amorphous silicon technology, which comprises a crystalline silicon substrate, wherein the front surface of the crystalline silicon substrate comprises at least one passivation layer; the back surface of the crystalline silicon substrate comprises a tunneling oxide layer, n + doped amorphous silicon layers/p + doped amorphous silicon layers which are arranged alternately, a laser grooving region, a passivation layer and a metal electrode from inside to outside. The solar cell adopts a cell structure combining a back contact mode and a heterojunction mode, optimizes a doped amorphous silicon growth mode, improves the passivation capacity and the contact capacity of the solar cell under the characteristic of reserving IBC high short-circuit current, and simultaneously effectively reduces the manufacturing cost. The verification proves that the efficiency of the mass production HBC battery adopting the structure of the invention reaches more than 25% of conversion efficiency, the open-circuit voltage reaches more than 710mV, and the mass production conversion efficiency is higher than 23.5% of the mass production conversion efficiency of the current mainstream heterojunction or TOPCon technology.

Description

A high-efficiency doped amorphous silicon technology based on LPCVD interdigitated back contact Mass junction solar cell

technical field

The invention relates to the technical field of solar cells, and provides a growth method for a low-cost, high-quality doped amorphous silicon passivation layer. It is especially suitable for the formation of doped amorphous silicon passivation layers in interdigitated back-contact heterojunction solar cells (HBC).

Background technique

In recent years, the energy crisis and environmental pressure have promoted the rapid development of solar cell research and industry. At present, crystalline silicon solar cells are the most mature and widely used solar cells, accounting for more than 90% of the photovoltaic market, and will occupy a dominant position for a long time in the future. In the rapidly developing photovoltaic industry, the improvement of photoelectric conversion efficiency and the reduction of cell manufacturing costs have become the fundamentals of the entire photovoltaic industry. With the continuous progress of photovoltaic cell technology, more and more high-efficiency solar cells have entered people's field of vision.

The HBC battery has both the high short-circuit current of the IBC battery and the high open voltage of the HJT battery. The laboratory conversion efficiency is as high as 26.63%, and its development potential has been proved.

There is no metal electrode on the front surface of the HBC battery structure, and the P and N layers on the back show an orderly and regular staggered arrangement, which greatly reduces the series resistance Rs, and the metal electrodes in contact with the P and N layers can form a good ohmic contact. short-circuit current. In addition, the excellent intrinsic passivation layer can achieve high open circuit voltage.

In the currently reported HBC cells, the doped amorphous silicon passivation layer is the core step, and the PECVD amorphous silicon coating or ion implantation technology is currently used in the market. The current mainstream technology is the PECVD technology route. Meyer Burger, Ideal Energy, and American Applied Materials are the current major suppliers. Their equipment costs are extremely high, the battery production cost is very high, and the road to mass production is relatively long. There is a need for an HBC battery structure that can be combined with the current mass production technology to achieve rapid popularization and application of high-efficiency technology.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an interdigitated back-contact heterojunction solar cell based on LPCVD-based high-efficiency doped amorphous silicon technology in view of the problems existing in the background technology.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is:

An interdigitated back-contact heterojunction solar cell based on LPCVD high-efficiency doped amorphous silicon technology, comprising a crystalline silicon substrate, and a front surface of the crystalline silicon substrate includes at least one passivation layer; The back surface of the silicon substrate includes a tunnel oxide layer, an alternately arranged n+-doped amorphous silicon layer/p+-doped amorphous silicon layer, a laser grooved region, a passivation layer and a metal electrode from the inside to the outside.

Further, the crystalline silicon substrate is any one of an N-type single crystal silicon substrate or a P-type single crystal silicon substrate.

Further, the front surface of the crystalline silicon substrate is a textured surface, and the back surface is either an acid polished surface or an alkali polished surface.

Further, the passivation layer provided on the front surface of the crystalline silicon substrate is one or a combination of SiO2, AlOx, SiNx, and SiONx.

Further, the tunnel oxide layer on the back surface of the crystalline silicon substrate is prepared by any one of atmospheric pressure thermal oxygen oxidation and LPCVD thermal oxygen oxidation.

Further, the alternately arranged n+ doped amorphous silicon layers/p+ doped amorphous silicon layers are realized by LPCVD doping technology, wherein B doping is realized by using BCl3 gaseous doping source.

Further, the n+ doped amorphous silicon layer and the p+ doped amorphous silicon layer are alternately realized by using a mask and a laser grooving technology respectively.

Further, the passivation layer on the back surface of the crystalline silicon substrate is one or a combination of SiNx and SiONx.

Further, the metal electrode is silver paste.

The beneficial effects of the present invention are:

(1) The present invention adopts the battery structure combining the back contact method and the heterojunction method, optimizes the growth method of doped amorphous silicon, improves the passivation ability and contact ability of the solar cell while retaining the characteristics of high short-circuit current of IBC, and at the same time Effectively reduce the manufacturing cost. It has been verified that the mass-produced HBC cell using the structure of the present invention has a conversion efficiency of more than 25% and an open circuit voltage of more than 710mV, which is higher than the 23.5% mass-produced conversion efficiency of the current mainstream heterojunction or TOPCon technology.

(2) The HBC cell of the present invention is based on the LPCVD high-efficiency doped amorphous silicon technology. Compared with the prior art, the LPCVD doping technology and the mask slotting technology are used to realize the n+-doped amorphous silicon layer and the p+-doped amorphous silicon layer respectively. Amorphous silicon layer, this technology retains the characteristics of the front surface of the interdigitated back contact battery without shielding and high short-circuit current, and at the same time realizes the passivation contact ability on the back side, which greatly improves the open circuit voltage of the battery, and mass-produces the HBC battery. The efficiency reaches more than 25%, and the battery open circuit voltage reaches more than 710mV.

(3) In the present invention, especially in the preparation of the doped amorphous silicon layer, the n+ doped amorphous silicon layer is prepared by using the LPCVD method in the existing TOPCon technology, and the low temperature p+ doped amorphous layer is realized by using the BCl3 gaseous source at the same time, In addition, the doping concentration is easy to control, and more importantly, the manufacturing cost is reduced, and a solution that can be combined with the existing TOPCon mass production technology is provided, which can realize the rapid technical upgrade of the mass production line.

Description of drawings

FIG. 1 is a cross-sectional view of the HBC cell structure of the present invention.

Labels in the figure: crystalline silicon substrate 1, passivation layer 2, tunnel oxide layer 3, n+ doped amorphous silicon layer 4, p+ doped amorphous silicon layer 5, laser grooved region 6, passivation layer 7, Metal electrode 8.

Detailed ways

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings. It should be noted that the specific embodiments are only detailed descriptions of the present invention and should not be regarded as limitations of the present invention.

As shown in FIG. 1, an interdigitated back-contact heterojunction solar cell based on LPCVD high-efficiency doped amorphous silicon technology includes a crystalline silicon substrate 1. In this embodiment, the crystalline silicon substrate 1 It is an N-type single crystal silicon substrate or a P-type single crystal silicon substrate. The front surface of the crystalline silicon substrate 1 is a single crystal solar cell, and conventional KOH or NaOH is used to make a textured surface to obtain the required textured reflectivity. It should be less than 11% so that better light absorption and optimal short-circuit current can be obtained. The back surface of the crystalline silicon substrate adopts either an acid polishing surface prepared with 2:1:5 HNO3/HF/H2O or a KOH alkali polishing surface with a concentration of 49%, and the back surface requires a reflectivity greater than 30%. And after 5-10min O3 cleaning to achieve the optimal surface state, reduce the surface recombination that may be caused by pollution, and provide better conditions for the subsequent passivation process.

The front surface of the crystalline silicon substrate 1 includes at least one passivation layer 2 ; the back surface of the crystalline silicon substrate 1 includes a tunnel oxide layer 3 and n+ doped amorphous silicon alternately arranged from inside to outside. Layer 4 and p+ doped amorphous silicon layer 5 , laser grooved region 6 , passivation layer 7 and metal electrode 8 .

The passivation layer on the front surface of the crystalline silicon substrate 1 is one or a combination of SiO2, Al2O3, Si3N4, and SiON, and the passivation film can choose to use the no-wrap plating technology to reduce the influence of the backside wrapping. The preparation of passivation film can be realized by horizontal PECVD equipment.

The tunnel oxide layer on the back surface of the crystalline silicon substrate 1 is prepared by any one of atmospheric pressure thermal oxygen oxidation and LPCVD thermal oxygen oxidation. carrier tunneling effect.

The n+ doped amorphous silicon layer and the p+ doped amorphous silicon layer can be realized by LPCVD doping technology, wherein the B doping is realized by using BCl3 gaseous doping source, the n+ doped amorphous silicon layer and the p+ doped amorphous silicon layer are realized. The crystalline silicon layer is alternately realized by mask and laser slotting technology. Specifically, a layer of n+ doped amorphous silicon layer is first formed through mask and laser slotting, and then a layer of n+ doped amorphous silicon layer is formed through mask and laser slotting. p+ doped amorphous silicon layer, ..., and so on.

Specifically, in the process of adopting LPCVD doping technology, the reaction source used is the reaction of BCl3 gas and SiH4 gas, and the main steps are:

Step 1: Open the furnace door of the LPCVD equipment and put the samples of doped amorphous silicon into the carrier, and the equipment is evacuated.

Step 2: Under the condition that the vacuum is kept at 200-500mtorr, the temperature is raised to 500-600°C and kept at a constant temperature for several times, so that the silicon wafer can be heated under low pressure and stabilized, and the surface of the silicon wafer can be kept clean under vacuum.

Step 3: The BCl3 gas of 10-200 sccm and the SiH4 gas of 300-700 sccm are introduced into the reaction source, and the amorphous silicon is continuously grown for 60-180 minutes.

Step 4: Purge the special gas pipeline with N2, and at the same time lower the temperature to below 500 ℃, and pass N2 to back pressure the furnace tube to normal pressure.

Step 5: The sample production of the furnace door is completed.

In the embodiment of the present invention, the passivation layer on the back surface of the crystalline silicon substrate adopts one or a combination of Si3N4 and SiON. Different from the front surface, there is no need to use an Al2O3 passivation film here, because the Al2O3 film has a There are negative charges on the back of the N-type cell to form an inversion, which is not conducive to the transport of carriers.

In the embodiment of the present invention, the metal electrode is silver paste.

The HBC battery prepared by the invention retains the features of the interdigitated back contact battery with no shielding on the front surface and high short-circuit current, and at the same time realizes the passivation contact ability on the back surface, greatly improving the open circuit voltage of the battery. The electrical properties of the prepared HBC cells were tested by standard solar cell testing methods. The mass-produced HBC cells had an efficiency of over 25% and an open circuit voltage of over 710 mV.

Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims (9)

1. An interdigital back contact heterojunction solar cell based on LPCVD (low pressure chemical vapor deposition) high-efficiency doped amorphous silicon technology is characterized by comprising a crystalline silicon substrate, wherein the front surface of the crystalline silicon substrate comprises at least one passivation layer; the back surface of the crystalline silicon substrate comprises a tunneling oxide layer, n + doped amorphous silicon layers/p + doped amorphous silicon layers which are arranged alternately, a laser grooving region, a passivation layer and a metal electrode from inside to outside.

2. The interdigital back-contact heterojunction solar cell based on LPCVD-based highly efficient doped amorphous silicon technology according to claim 1, characterized in that the crystalline silicon substrate is any one of an N-type monocrystalline silicon substrate or a P-type monocrystalline silicon substrate.

3. The interdigital back-contact heterojunction solar cell based on LPCVD-based highly efficient doped amorphous silicon technology, according to claim 1, wherein the front surface of the crystalline silicon substrate is textured, and the back surface is any one of acid polished surface or alkali polished surface.

4. The interdigital back contact heterojunction solar cell based on LPCVD (low pressure chemical vapor deposition) -based high-efficiency doped amorphous silicon technology is characterized in that the passivation layer arranged on the front surface of the crystalline silicon substrate is one or a combination of SiO2, AlOx, SiNx and SiONx.

5. The interdigital back-contact heterojunction solar cell based on LPCVD-based high-efficiency doped amorphous silicon technology according to claim 1, wherein the tunnel oxide layer on the back surface of the crystalline silicon substrate is prepared by any one of atmospheric thermal oxidation and LPCVD thermal oxidation.

6. The interdigital back-contact heterojunction solar cell based on LPCVD-based high-efficiency doped amorphous silicon technology according to claim 1, wherein the alternating n + doped amorphous silicon layer/p + doped amorphous silicon layer is implemented by LPCVD doping technology, wherein B doping is implemented by using BCl3 gaseous doping source.

7. The interdigital back-contact heterojunction solar cell based on LPCVD highly efficient doped amorphous silicon technology according to claim 1, wherein the n + doped amorphous silicon layer and the p + doped amorphous silicon layer are alternately implemented by using mask and laser grooving technologies, respectively.

8. The interdigital back contact heterojunction solar cell based on LPCVD-based highly efficient doped amorphous silicon technology, in accordance with claim 1, wherein the back surface passivation layer of crystalline silicon substrate is one or a combination of SiNx and SiONx.

9. The LPCVD-based high efficiency doped amorphous silicon technology based interdigital back contact heterojunction solar cell of claim 1, characterized in that the metal electrode is silver paste.

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