1 Introduction
It is well known that there are many advantages in the use of solar energy. The photovoltaic power generation will provide the main energy source for humans. However, in the current market, it is necessary to make the solar power generation market. It is accepted by the majority of consumers, improve the photoelectric conversion efficiency of solar cells, and reduce production. The cost should be the biggest goal we pursue. From the current development process of the international solar cell, it can be seen that its development trend is single crystal silicon, polysilicon, strip silicon, film material (including microcrystalline silicon-based film, compound based film and dye film. ). From the perspective of industrialization, the center of gravity has been developed from single crystal to the polycrystalline direction. The main reasons are; [1] The head tail of the solar cell can be increasing; [2] For the solar battery, square substrate is more Combined, polysilicon obtained by casting method and direct solidification method can directly obtain square materials; [3] polysilicon production process continuously, the automatic casting furnace can produce more than 200 kg of silicon ingot per production period (50 hours), The size of the grain reached a centimeter; [4] Due to the study and development of single crystal silicon technology in the past decade, the process is also applied to the production of polysilicon batteries.
A-Si: Hanyan Battery The appearance is like a dawn, illuminating the road to the application of the solar cell to the application. After more than ten years of development, its preparation process is getting more stable and mature, its smart structure and cheap Preparation Process To people's description: Solar needs to replace energy from supplement energy, this structural design technology and preparation method must adopt, otherwise the expensive price of solar cell will become its development bottleneck. This paper describes the structural design and preparation analysis of the A-Si: H solar cell, and discusses the process parameters affecting its performance.
2 large-scale single knot integrated A-Si: structural design of H solar cell
2.1 A-Si: H solar battery structure
A-Si: h solar cell is a flat optical exchange device for forming a non-alcoholic silicon PIN structure on a glass substrate, and the structure of a single battery is shown in Figure 1, when the sun is irradiated on the battery, Battery absorption light can produce electron-hole pair, under the internal construction of the photovoltaic battery, the optical electron and holes are separated, and the alternative charge accumulation occurs at both ends of the photovoltaic cell, that is, the optical voltage, if the electrode is taken out, and the electrodes are taken out on both sides On the load, there is a light current flowing in the load to obtain a power output. Figure 2 shows an equivalent circuit of a A-Si: H solar cell. The IL is a light current, the ID is a diode of the diode, and the RSH is a parallel resistance, and RS is a series resistance, and RL is a load resistance.
At present, the open circuit voltage UOC of the A-Si: H is about 0.8V, the working voltage Um is about 0.55V, and the short-circuit current density JSC is about 13.4mA / cm2, and the working current density JM is about 11mA / cm2. Such small The electric energy output is basically no use. To output a higher voltage and large current, a valid series parallel measures must be taken.
Figure 1A-S: H Single Battery Structure Figure 2A-S: H Solar Battery Equivalent Circuit
2.2 Integrated A-Si: Structure Design of H Solar Battery
In order to obtain a certain power output, many A-Si: h solar batteries must be effectively stringed in parallel, however, A-Si: h solar cell is a thin film device, and the lead series is neither reliable. Therefore, it is necessary to consider internal integration when prepared. Figure 3 shows its internal integration structure diagram. 1, 2, 3, 4 is four single cells, in the form of a series, and the current flow direction is shown in the figure.
Figure 3 Integrated A-Si: internal structural diagram of H solar cell
To design a A-Si: h solar battery assembly that charges 6V, 4ahvrla battery, then the desired solar cell module is:
UM ≥ 3UT + UD = 8V
Where: UT is the overchard threshold voltage of the VRLA battery, and UD is a forward voltage drop of anti-refrigeration diodes.
Since the operating voltage of the H solar cell is about 0.55V, at least 15 batteries are required in series, if the current of C / 10 is charged, the desired A-Si: h solar battery assembly output current At least more than 400mA, then the area of the single solar cell should be at least more than 37 cm2, in consideration of the area occupied by the inner series wiring, the area of the final single solar cell is taken from 151 cm2.
Therefore, the required A-Si: h solar battery assembly is a solar cell having a single battery area of 151 cm2.
3 major area single knot integrated A-Si: preparation analysis of H solar cells
The A-Si: h solar cell is organically bonded by a multilayer film, and it is prepared according to the process of the process of Fig. 4.
Figure 4A-S: H solar battery process sequence
3.1TCO preparation
TCO glass refers to a component formed by a transparent Conductive Oxide that is uniformly plated by a physical or chemical coating method in a flat glass surface. For thin film solar cells, since the intermediate semiconductor layer has almost no transverse electrical conductivity, the Tco glass must be used to effectively collect the current of the battery, and the TCO film has a high transmissive and reduced function to enable most of the light into the absorbent layer. The production process of TCO glass is mainly divided into ultra-white float glass production, TCO coating. Ultra-white float glass production process is difficult, currently the world's main suppliers have Japanese Asahi Nidan, US PPG, San Gogban, etc., domestic supply manufacturers limited, currently Gold Crystal Technology, Nanbang, and Xinyi can be supplied.
TCO is a suede SnO2: F film, which can be prepared from a chemical vapor deposition (CVD) process, and the preparation is good, high transmittance, fresh, non-polluting, waterless corroded float glass is made of substrate, Cutting the area size of the above calculation, after the washing is dried into the CVD furnace to start deposition, the chemical reaction that occurs is as follows:
SNCL4 + O2 = SNO2 + 2CL2
SNCL4 + 2H2O = SNO2 + 4HCL
After the deposition, it is placed on the platform of the tantylumium garnet laser to perform laser scrapping, and how much is determined by the required series battery.
3.2P layer preparation
The P layer ingredients are A-Si: H: B: C, the preparation process is plasma enhanced chemical vapor deposition (PECVD), which is a high frequency (13.56 MHz) glow discharge physical process and chemical reaction combined with the chemical reaction. The advantage of this method is that the deposition rate is fast, the film formation is good, the needle hole is less, and the gas source of the deposition is SiH4, CH4, B2H6, and HE. B2H6 is used to achieve a mixture of materials, and HE is used as a dilution gas, and CH4 is used to improve the optical properties of the P layer. By changing the gas partial pressure ratio during the deposition process, a P layer having a different amount of C is obtained (a-Si: H: B: C) film can be obtained, and the different C is contained, and there is a different photoelectric properties.
3.3I layer preparation
The I. Ingredients of I-Si: h, the preparation process is still PECVD, the deposition of the gas source is SiH4 and H2. The presentation is the generating area of the photovoltaic current, and thus its film formation quality directly affects A-Si: h solar cell Performance, its performance is mainly determined by the preparation of discharge power, matrix temperature, reaction pressure, and gas flow. During the film formation process, low discharge power is used to improve the photoelectron performance of the film at a constant film formation rate.
3.4N layer preparation
The N layer is A-Si: H: p, the deposited gas source is a mixed gas of SiH4, pH3, H2 and He, wherein the pH 3 is used to achieve a mixture of materials. A-Si: H: p film structure and photoelectric properties with matrix temperature, gas source ratio, reaction pressure, discharge power, and gas flow, etc. are closely related.
During the preparation of the above-mentioned film, the reaction pressure, the discharge time, the gas flow, and the reaction chamber temperature are automatically monitored and controlled by the computer, and the required control parameters are implemented by the software.
After the film was prepared, the components were placed in the mechanical comb. The width should be less than 0.2mm. The silicon should be close to the nearby laser engrave, the tolerance of the two is 0.2 ~ 0.7mm. The pulling rate should be greater than 80%, and the purpose is to form the amorphous silicon layer of each single battery and allow Al and TCO good contact.
3.5 steamed aluminum
The Al electrode is made by vacuum evaporation, in the integrated A-Si: h solar cell, aluminum is not only used as the negative electrode of each sub-battery, but it connects each unit cell in structure. In addition, the aluminum film can also reflect the long wave limit photon absorbed by the amorphous silicon alloy layer, increase the utilization of the solar cell to the light.
The integrated A-Si: h solar battery assembly prepared according to the above requirements, and the battery output characteristics measured on the solar cell test bench of CHRONAR in the United States are shown in Figure 5. The test conditions were: standard light intensity, AM 1.5, 100 mW / cm2, 25 ° C. From the perspective, it reached the design requirements.
Figure 5 Experimental integrated A-Si: Output characteristics of H solar cells
4 Conclusion
The integrated A-Si: h solar cell structure is simple, the preparation process is low, easy to design into different forms to meet different user needs. Its appearance has greatly promoted the development of the entire solar battery industry. , Reading the full text, the technology area
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