共查询到19条相似文献,搜索用时 375 毫秒
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采用等离子体增强化学沉积的方法(PECVD),在低衬体温度下制备不同厚度的双面氮化硅薄膜,通过准稳态电导法(QSSPCD)测试non-diffused和diffused硅片沉积不同厚度双面氮化硅薄膜烧结前后的少子寿命,研究发现,氮化硅薄膜厚度在17 nm左右的时候,背面钝化效果有所下降,超过26 nm的时候,效果基本一致.non-diffused烧结后的少子寿命下降很大,而diffused与之相反.结果表明,采用氮化硅作为背面钝化介质膜,可以改善材料的少子寿命,背面钝化膜可以选择在26~75 nm之间. 相似文献
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The gettering during an emitter diffusion in multicrystalline silicon is improved by adding a low-temperature tail to the standard diffusion. The tail keeps the emitter sheet resistance within the usable range for solar cells. An increase in minority carrier lifetime by a factor ten is obtained. Decrease in recombination activity of grain boundaries and decrease in interstitial iron concentration are mainly responsible for this improved lifetime. The proposed mechanisms for this improvement are: reduction of size of precipitates because of the longer duration, possibly assisted by beneficial changes in thermodynamics and kinetics of the gettering because of the low temperature. 相似文献
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Application of phosphorus diffusion gettering process on upgraded metallurgical grade Si wafers and solar cells 总被引:1,自引:0,他引:1
Although phosphorus (P) diffusion gettering process has been wildly used to improve the performance of Si solar cells in photovoltaic technology, it is a new attempt to apply P diffusion gettering process to upgraded metallurgical grade silicon (UMG-Si) wafers with the purity of 99.999%. In this paper, improvements on the electrical properties of UMG-Si wafers and solar cells were investigated with the application of P diffusion gettering process. To enhance the improvements, the gettering parameters were optimized on the aspects of gettering temperature, gettering duration and POCl3 flow rate, respectively. As we expected, the electrical properties of both multicrystalline Si (multi-Si) and monocrystalline Si (mono-Si) wafers were significantly improved. The average minority carrier lifetime increased from 0.35 μs to nearly about 2.7 μs for multi-Si wafers and from 4.21 μs to 5.75 μs for mono-Si wafers, respectively. Accordingly, the average conversion efficiency of the UMG-Si solar cells increased from 5.69% to 7.03% for multi-Si solar cells (without surface texturization) and from 13.55% to 14.55% for mono-Si solar cells, respectively. The impurity concentrations of as-grown and P-gettered UMG-Si wafers were determined quantitively so that the mechanism of P diffusion gettering process on UMG-Si wafers and solar cells could be further understood. The results show that application of P diffusion gettering process has a great potential to improve the electrical properties of UMG-Si wafers and thus the conversion efficiencies of UMG-Si solar cells. 相似文献
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Multicrystalline Si for photovoltaic applications is a very inhomogeneous material with localized regions of high dislocation density and large impurity and precipitate concentrations which limit solar cell efficiency by acting as carrier recombination sites. Due to slow dissolution of precipitates in multicrystalline Si, these regions cannot be improved by conventional P and Al gettering treatments for removal of metal impurities which give good results for single crystal Si. It is shown that an extended high temperature Al gettering treatment can improve minority carrier diffusion lengths in these low quality regions and homogenize the electrical properties of multicrystalline Si wafers. 相似文献
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Daniel Chen Matthew Edwards Stuart Wenham Malcolm Abbott Brett Hallam 《Frontiers in Energy》2017,11(1):23-31
One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry highly reliant on heavily doped phosphorus diffusions as a source of gettering, the transition to selective emitter structures would require new alternative methods of impurity extraction. In this paper, a novel laser based method for gettering is investigated for its impact on commercially available silicon wafers used in the manufacturing of solar cells. Direct comparisons between laser enhanced gettering (LasEG) and lightly-doped emitter diffusion gettering demonstrate a 45% absolute improvement in bulk minority carrier lifetime when using the laser process. Although grain boundaries can be effective gettering sites in multicrystalline wafers, laser processing can substantially improve the performance of both grain boundary sites and intra-grain regions. This improvement is correlated with a factor of 6 further decrease in interstitial iron concentrations. The removal of such impurities from multicrystalline wafers using the laser process can result in intra-grain enhancements in implied open-circuit voltage of up to 40 mV. In instances where specific dopant profiles are required for a diffusion on one surface of a solar cell, and the diffusion process does not enable effective gettering, LasEG may enable improved gettering during the diffusion process. 相似文献
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N. Khedher M. Hajji M. Hassen A. Ben Jaballah B. Ouertani H. Ezzaouia B. Bessais A. Selmi R. Bennaceur 《Solar Energy Materials & Solar Cells》2005,87(1-4):605
The possible benefits of phosphorus-based gettering applied to crystalline silicon wafers have been evaluated. The gettering process is achieved by forming porous silicon (PS) layers on both sides of the Si wafers. The PS layers were formed by the stain-etching technique, and phosphorus diffusion using liquid POCl3-based source was done on both sides of the Si wafer. The realized phosphorus/PS/Si/PS/phosphorus structure undergoes a heat treatment in an infrared furnace under an O2/N2 controlled atmosphere. This heat treatment allows phosphorus to diffuse throughout the PS layer and to getter eventual metal impurities towards the phosphorus doped PS layer. The gettering effect was evaluated using four probe points, Hall effect measurements and the light beam induced current (LBIC) technique. These techniques enable to measure the density and the mobility of the majority carrier and the minority carrier diffusion length (Ld) of the Si substrate. We noticed that the best gettering is achieved at 900 °C for 90 min of heat treatment. After gettering impurities, we found an apparent enhancement of the mobility and the minority carrier diffusion length as compared to the reference substrate. 相似文献
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The various polycrystalline silicon materials (cast ingots, ribbons) which are commercially available for the solar cells manufacturing differ very much among themselves due to the different growth processes. The resulting microstructure and impurity content will influence differently the material characteristics during thermal treatments inherent to the device manufacturing. As the gettering efficiency depends on the kind of polycrystalline material, the variations observed in the optimal gettering conditions or passivation will be discussed. In this paper, we compare the performances of various types of polycrystalline silicon upon classical and rapid thermal-process-induced co-diffusion of phosphorus and aluminium. We show that a large bulk minority carrier diffusion length enhancement occurs in the case of co-diffusion when compared to the separate diffusion of phosphorus and aluminium. 相似文献
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J. Boudaden M. Loghmarti D. Ballutaud A. Rivire R. Lüdemann A. Slaoui J. C. Muller 《Solar Energy Materials & Solar Cells》2001,65(1-4)
The electrical properties of boron-doped multicrystalline silicon for photovoltaic applications, elaborated by the cold crucible pulling process, are studied by the photoconductivity decay method and the electron beam-induced current measurement technique. The bulk lifetime mapping of the minority carriers in the as-grown silicon wafers is drawn up using both the techniques. Moreover, the consequence of phosphorus doping on the recombination properties of extended defects are studied using the EBIC measurements. Two different treatments are investigated in order to improve the electrical properties of the as-grown silicon wafers: (a) thermal phosphorus diffusion, for which the gettering efficiency is determined by the different treatment parameters; (b) remote plasma hydrogen passivation which leads to increase of the minority carrier lifetime. 相似文献
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Abdalla A. Alnajjar 《Renewable Energy》2000,20(4)
The effect of the annealing ambient on the efficiency of the phosphorous gettering process for Czochralski (CZ) silicon wafers is investigated in this paper. Phosphorous is diffused from a POCl3 source at different temperatures into single-crystal p-type silicon wafers having a resistivity of around 1 ohm/cm. This is followed by an additional heat treatment in either oxidizing (wet and dry oxide) or in inert (argon) ambient. The laser microwave photoconductivity decay method is used to monitor the changes in the minority carrier lifetime after the phosphorous diffusion and the subsequent annealing. Furthermore, solar cells are fabricated on the treated samples in order to correlate the lifetime measurements with the illuminated I-V characteristics of the cells. 相似文献
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Lifetime of minority carriers has been widely identified to be the key material parameter determining the conversion efficiency of pn-junction silicon solar cells. Impurities and defects in the silicon crystal lattice reduce the charge carrier lifetime and thus limit the performance of the solar cells. Removal of impurities by silicon material purification is often contradictory with low cost production of photovoltaic devices. In this paper, we present experimental results of an efficient gettering technique which can be applied to low cost processing of multicrystalline silicon solar cells without any additional process steps or compromises with optimal device design parameters. This technique is based on well-known phosphorous gettering. We have discovered that if the silicon wafers are kept in the furnace after the emitter diffusion at the 700°C, significant improvement in the lifetime will take place. At this temperature the properties of the pn-junction remain unaffected meanwhile many lifetime killers are still mobile. The time needed for this temperature program can be easily modified in order to respond to the material quality variations in substrates originating from different parts of multicrystalline ingot. Better control of lifetime can lead to higher degree of starting material utilization. 相似文献