Abstract : The effects of different resistances on the electrical properties of high-resistivity solar cells are studied. The short-circuit current (Isc) and open-circuit voltage (Uoc) of the high-resistance cells increase linearly with the increase of the diffusion resistance. The fill factor (FF) decreases linearly with the increase of the diffusion resistance, and the photoelectric conversion efficiency (Eta) decreases rapidly as the diffuser resistance first increases to the peak. 0 Preface Solar cells are a huge semiconductor diode that is based on semiconductor materials for energy conversion. At present, silicon solar cells still dominate the photovoltaic industry. Solar cells commonly use silicon crystals as the substrate, usually a cylindrical monocrystalline silicon rod is cut into pieces, so the quality of the silicon wafer determines the performance of solar cells to a large extent. Industrial silicon is produced by carbon reduction from quartz sand, but the purity of industrial silicon at this time is not very high. It also contains a lot of metal impurities such as iron, aluminum, calcium, magnesium, etc.; then, these impurities are removed by further purification. The pure polysilicon is deposited and reduced, and the purity of the polysilicon does not reach the purity of the silicon wafer required by the solar cell. Therefore, the monocrystalline silicon needs to be further purified. At present, most of the single-crystal silicon manufactured by the Czochralski method is used, the polysilicon is heated and melted in a quartz crucible, a dopant is added, and a small piece of seed crystal is used to pull out the cylindrical single-crystal silicon from the molten silicon. Due to different doping concentrations, the resistivity of single crystal silicon will also be different. The range of resistivity of silicon wafers is quite broad. For solar cells, silicon wafers with lower resistivity can obtain higher open-circuit voltage and photoelectric conversion efficiency, and open-circuit voltage of solar cells made of high-resistivity silicon wafers. Lower, which leads to lower fill factor, so the conversion efficiency is low [1, 2]. In recent years, China's silicon wafer production technology has made considerable progress, but it is still unable to accurately control the silicon wafer resistivity value, can only control the resistivity of the silicon wafer within a certain range, so for some high resistance The rate of silicon requires people to understand more about their performance and improve their photoelectric conversion efficiency [3-5]. 1 experiment In this paper, 210 high-resistivity single-crystal silicon wafers with a resistivity in the range of 3.5-4.5Ω·cm were selected. The specifications were 156mm×156mm and the thickness was 200μm. Firstly, the suede structure was prepared on the surfaces of 210 silicon wafers by alkali etching. That is to say, thousands of small pyramids were made on the surface of silicon by anisotropic etching of silicon to form light traps, increase light absorption, and increase the short circuit current of the battery. And conversion efficiency. After the cleaning, the pn junction is formed, that is, the surface of the silicon wafer is doped with an impurity layer that is different from the conductivity type of the silicon substrate matrix. At present, a common method for silicon solar cells is to dope V-group impurities in P-type silicon or do III-group in N-type silicon at high temperatures. Impurities, due to the high temperature effect of impurity elements through the thermal diffusion movement into the substrate, and the concentration of impurities and the depth of the pn junction due to the impurity element type, initial concentration and diffusion temperature vary. This distribution of diffusion has a great influence on the electrical properties of the battery. Due to different processes, the diffusion distribution pattern is also different. In the diffusion process, 210 wafers were divided into 7 groups. These 7 groups diffused respectively. The final square resistances of the 7 groups were 70Ω, 75Ω, 80Ω, 85Ω, 90Ω, 100Ω, and 105Ω, respectively. The back junctions are then removed separately and the anti-reflective film is formed by chemical vapor deposition. Finally, the electrodes are printed by screen printing and sintered into sheets. Take these 7 groups of battery blocks with different resistances for electrical performance testing and collect electrical performance data separately. 2 The principle of liquid source diffusion Nowadays, the diffusion process commonly used in solar cells is the diffusion of phosphorus oxychloride liquid source. The liquid phosphorus source has two mechanisms of vacancy diffusion and substitutional interstitial diffusion. Phosphorus oxychloride is a colorless, transparent liquid with a strong irritating odor. It is toxic, has a melting point of 2°C and a boiling point of 107°C. It emits fumes in humid air and is extremely volatile and prone to hydrolysis. Therefore, special attention should be paid to the sealing of source bottles for the use of phosphorus oxychloride [56]. Phosphorus oxychloride is decomposed into phosphorus pentachloride and phosphorus pentoxide at a high temperature. The resulting phosphorus pentoxide is further reacted with silicon to form silicon dioxide and phosphorus. When the phosphorus oxychloride is thermally decomposed, if there is no external oxygen Participation, its decomposition is not sufficient, the generated phosphorus pentachloride is not easy to decompose, and has a corrosive effect on silicon, destroy the surface of the silicon, but if oxygen is added, phosphorus pentachloride will further decompose to generate phosphorus pentoxide and chlorine, The generated phosphorus pentoxide is further reacted with silicon to form silicon dioxide and phosphorus. Therefore, in the phosphorus diffusion, in order to promote the full decomposition of phosphorus oxychloride and avoid the corrosion of phosphorus pentachloride on the surface of the silicon wafer, nitrogen gas must be used. At the same time, when oxygen is supplied and oxygen is abundant, phosphorus oxychloride is thermally decomposed to generate phosphorus pentoxide and chlorine. Phosphorus pentoxide produced by decomposition of phosphorus oxychloride is deposited on the surface of the silicon wafer, and phosphorus pentoxide reacts with silicon to form two. Silicon oxide and phosphorus, and the formation of a layer of phosphosilicate glass on the surface of the silicon, then the phosphorus in the diffusion of silicon [7,8]. The phosphorus oxychloride liquid source diffusion device is shown in Figure 1. 3 Results and Analysis The parameters used to characterize the output characteristics of the solar cell are the short circuit current Isc, the open circuit voltage Uoc, and the fill factor FF. The inherent resistivity of solar cells affects its output characteristics to some extent. The experimental results show that for the high-resistivity solar cells, the short-circuit current Isc and the open-circuit voltage Uoc of the output characteristics will increase linearly with the increase of the square resistance, as shown in Fig. 2 and Fig. 3; the fill factor FF will follow the equation. The increase in resistance slows down The trend is shown in Fig. 4. The conversion efficiency Eta, with the increase of the square resistance, begins to grow slowly and reaches a peak and then rapidly decreases, as shown in Fig. 5. (Author: JA Solar Co., Ltd., Wang Hui) Wardrobe Cabinet Handle,Indoor Door Handle,Simple Retro Wardrobe Handle,Recessed Door Handle Zhaoqing Muyi Hardware Products Co., Ltd , https://www.muyihardware.com
Influence of different resistance on the electrical properties of high resistivity solar cells