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1.
    
High‐quality Ga‐doped ingots are grown in different casting furnaces at optimized growth parameters; 3·5 kg ingots exhibit normal distribution of diffusion lengths along their height with very high diffusion lengths at the center of the ingot. Effective lifetimes as high as 1·1 ms are realized in 10 Ω cm Ga‐doped wafers after proper P‐diffusion and hydrogen passivation. Average effective lifetimes above 400 µs are also realized after P‐diffusion and hydrogen passivation for Ga‐doped wafers cut from 75 kg ingot where the response to P‐diffusion and hydrogen passivation is pronounced. High effective lifetimes are realized over the whole ingot with minimum values of 20 µs at the top of the ingot, indicating the possible use of about 85% of the ingot for solar cell production. Conversion efficiencies above 15·5% were realized in utilizing more than 80% of the ingot. High efficiencies of about 16% were realized in wafers with resistivities higher than 5 Ω cm p ‐type multicrystalline silicon wafers. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

2.
    
Light and elevated‐temperature induced degradation (LeTID) is currently a severe issue in passivated emitter and rear cells (PERC). In this work, we study the impact of surface texture, especially a black silicon (b‐Si) nanostructure, on LeTID in industrial p‐type mc‐Si PERC. Our results show that during standard LeTID conditions the b‐Si cells with atomic‐layer‐deposited aluminum oxide (AlOx) front surface passivation show no degradation despite the presence of a hydrogen‐rich AlOx/SiNx passivation stack on the rear. Furthermore, b‐Si solar cells passivated with silicon nitride (SiNx) on the front lose only 1.5%rel of their initial power conversion efficiency, while the acidic‐textured equivalents degrade by nearly 4%rel under the same conditions. Correspondingly, clear degradation is visible in the internal quantum efficiency (IQE) of the acidic‐textured cells, especially in the ~850 to 1100‐nm wavelength range confirming that the degradation occurs in the bulk, while the IQE remains nearly unaffected in the b‐Si cells. The observations are supported by spatially resolved photoluminescence (PL) maps, which show a clear contrast in the degradation behavior of b‐Si and acidic‐textured cells, especially in the case of SiNx front surface passivation. The PL maps also suggest that the magnitude of LeTID scales with surface area of the texture, rather than wafer thickness that was recently reported, although the b‐Si cells are slightly thinner (140 vs 165 μm). The results indicate that b‐Si has a positive impact on LeTID, and hence, benefits provided by b‐Si are not limited only to the excellent optical properties, as commonly understood.  相似文献   

3.
    
For photovoltaics, switching the p‐type dopant in silicon wafers from boron to indium may be advantageous as boron plays an important role in the light‐induced degradation mechanism. With the continuous Czochralski crystal growth process it is now possible to produce indium doped silicon substrates with the required doping levels for solar cells. This study aims to understand factors controlling the minority carrier lifetime in such substrates with a view to enabling the quantification of the possible benefits of indium doped material. Experiments are performed using temperature‐dependent Hall effect and injection‐dependent carrier lifetime measurements. The recombination rate is found to vary linearly with the concentration of un‐ionized indium which exists in the sample at room temperature due to indium's relatively deep acceptor level at 0.15 eV from the valence band. Lifetime in indium doped silicon is also shown to degrade rapidly under illumination, but to a level substantially higher than in equivalent boron doped silicon samples. A window of opportunity exists in which the minority carrier lifetime in degraded indium doped silicon is higher than the equivalent boron doped silicon, indicating it may be suitable as the base material for front contact photovoltaic cells.  相似文献   

4.
    
A systematic study of the variation in resistivity and lifetime on cell performance, before and after light‐induced degradation (LID), was performed along ∼900‐mm‐long commercially grown B‐ and Ga‐doped Czochralski (Cz) ingots. Manufacturable screen‐printed solar cells were fabricated and analyzed from different locations on the ingots. Despite the large variation in resistivity (0·57–2·5 Ω cm) and lifetime (100–1000 µ s) in the Ga‐doped Cz ingot, the efficiency variation was found to be ≤ 0·5% with an average efficiency of ∼17·1%. No LID was observed in these cells. In contrast to the Ga‐doped ingot, the B‐doped ingot showed a relatively tight resistivity range (0·87–1·22 Ω cm), resulting in smaller spread in lifetime (60–400 µ s) and efficiency (16·5–16·7%) along the ingot. However, the LID reduced the efficiency of these B‐doped cells by about 1·1% absolute. Additionally, the use of thinner substrate and higher resistivity (4·3 Ω cm) B‐doped Cz was found to reduce the LID significantly, resulting in an efficiency reduction of 0·5–0·6%, as opposed to >1·0% in ∼1 Ω cm ∼17% efficient screen‐printed cells. As a result, Ga‐doped Cz cells gave 1·5 and 0·7% higher stabilized efficiency relative to 1 and 4·3 Ω cm B‐doped Cz Si cells, respectively. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

5.
    
The defect‐induced diode breakdown behavior in multicrystalline silicon solar cells, which is located at recombination active crystal defects, is influenced by the surface texturization because the wet chemical treatment selectively etches grain boundaries and dislocations, resulting in etch pits. On textured surfaces, the defect‐induced breakdown voltage is decreased, and the slope of the local reverse I–V characteristics in breakdown is steeper. We find that the local defect‐induced breakdown voltage correlates with the depth of the etch pits. It is suggested that the enhanced electric field in the space charge region at the tip could be superimposed by an electric field around metallic precipitates because of the internal Schottky contact formation with the surrounding silicon. The combined electric field could be responsible for the dependence of the defect‐induced breakdown behavior on the surface texture. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
    
Ga doped ZnO (GZO) films prepared by sputtering at room temperature were rapid thermal annealed (RTA) at elevated temperatures. With increasing annealing temperature up to 570°C, film transmission enhanced significantly over wide spectral range especially in infrared region. Hall effect measurements revealed that carrier density decreased from ∼8 × 1020 to ∼ 3 × 1020 cm−3 while carrier mobility increased from ∼15 to ∼28 cm2/Vs after the annealing, and consequently low film resistivity was preserved. Hydrogenated microcrystalline Si (µc‐Si:H) and microcrystalline Si1‐xGex (µc‐Si1‐xGex:H, x = 0.1) thin film solar cells fabricated on textured RTA‐treated GZO substrates demonstrated strong enhancement in short‐circuit current density due to improved spectral response, exhibiting quite high conversion efficiencies of 9.5% and 8.2% for µc‐Si:H and µc‐Si0.9Ge0.1:H solar cells, respectively. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

7.
    
Boron‐doped crystalline silicon is the most relevant material in today's solar cell production. Following the trend towards higher efficiencies, silicon substrate materials with high carrier lifetimes are becoming more and more important. In silicon with sufficiently low metal impurity concentrations, the carrier lifetime is ultimately limited by a metastable boron–oxygen‐related defect, which forms under minority‐carrier injection. We have analysed 49 different Czochralski‐grown silicon materials of numerous suppliers with various boron and oxygen concentrations. On the basis of our measured lifetime data, we have derived a universal empirical parameterisation predicting the stable carrier lifetime from the boron and oxygen content in the crystalline silicon material. For multicrystalline silicon it is shown that the predicted carrier lifetime can be regarded as a fundamental upper limit. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

8.
    
The electrical properties and the minority charge carrier recombination behaviour of grain boundaries (GBs) and intragrain dislocations in different n‐type multicrystalline silicon (mc‐Si) ingots were systematically studied through microwave‐detected PhotoConductance Decay (µW‐PCD), Electron Beam Induced Current (EBIC) and PhotoLuminescence (PL) spectroscopy on as‐grown samples and on samples submitted to P‐diffusion step. It was confirmed that the overall quality of n‐type mc‐Si is high, indicating that n‐type‐Si is a valid source for photovoltaic applications. As expected, the average lifetime increases after the P‐diffusion process, which induces impurity gettering effects at the external surfaces, like in the case of p‐type samples, but an evident local increase of electrical activity of some GBs after that process was also observed using the EBIC mapping technique. Apparently, a redistribution of impurities occurs at the processing temperature and impurities are captured at the deepest sinks. In fact, while all GBs act as heterogeneous segregation/precipitation sites, some of them will compete with the external surfaces sinks, partly vanishing the effect of P‐gettering. Last but not least, it was experimentally demonstrated that the average lifetime values measured with the µW‐PCD technique well correlate with the recombination activity of GBs measured with the EBIC technique, showing the extreme importance of GBs on the effective lifetime of this material. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

9.
    
This paper elucidates the behavior and underlying mechanism of potential‐induced degradation (PID) on the rear side of p‐type monocrystalline silicon bifacial passivated emitter and rear cell (PERC) photovoltaic modules. At 50°C, 30% relative humidity, and −1000 V bias to the solar cells with aluminium foil on the rear glass surface, the rear‐side performance of bifacial PERC modules at standard testing conditions degraded dramatically after 40 hours with a 40.4%, 36.2%, and 7.2% loss in maximum power (Pmpp), short‐circuit current (Isc), and open‐circuit voltage (Voc), respectively. The front‐side standard testing condition performance, on the other hand, showed less degradation; Pmpp, Isc, and Voc dropped by 12.0%, 5.2%, and 5.3%, respectively. However, negligible degradation was observed when the solar cells were positively biased. Based on I‐V characteristics, electroluminescence, external quantum efficiency measurements, and the effective minority‐carrier lifetime simulation, the efficiency loss is shown to be caused by the surface polarization effect; positive charges are attracted to the passivation/antireflection stack on the rear surface and reduce its field effect passivation performance. Extended PID testing to 100 hours showed an increase in device performances (relative to 40 hours) due to the formation of an inversion layer along the rear surface. In addition, replacing ethylene‐vinyl acetate copolymer with polyolefin elastomer films significantly slows down the progression of PID, whereas a glass/transparent backsheet design effectively protects the rear side of bifacial PERC modules from PID. Furthermore, PID on the rear side of bifacial PERC modules is fully recoverable, and light greatly promotes recovery of the observed PID.  相似文献   

10.
    
In this work, we investigate the relationship between potential‐induced degradation (PID) and the bill of material used in module manufacturing. We manufacture samples with different combination of materials, using two types of solar cells (conventional vs PID‐free c‐Si cells), two types of ethylene‐vinyl acetate (EVA) films with low/high resistivity, and two types of backsheets with, respectively, low/high breathability properties, and subject the mini‐modules to extended PID testing. Our results clearly indicate that, when using a breathable polymeric backsheet, to have a “PID‐free” module the combination of PID‐free cells and high‐resistive EVA encapsulants is recommendable. The use of a conventional c‐Si cell in combination with a high‐resistive EVA encapsulant is still more effective than the use of PID‐free cells in combination with low‐quality EVA. Further, our results initially show that the breathability properties of the backsheet have apparently no influence on PID degradation. A second set of experiments using sandwich structures with increased resistance properties to water ingress (ie, glass and backsheets with barrier layers as rear covers and an edge sealant), however, indicates that preventing or reducing the diffusion of moisture in the encapsulant layer plays a role in further mitigating the impact of PID. This finding is supported by simulations of moisture ingress in the sandwich structures. Finally, we show that the use of a glass rear cover—compared with a polymeric backsheet—does not contribute in worsening the PID effect. On the contrary, by reducing moisture ingress in the front encapsulant layer, it delays the occurrence of PID.  相似文献   

11.
    
Comparison of minority carrier lifetime measurements carried out in transient mode with measurements performed under steady‐state conditions allows determination of the calibration constants needed in non‐transient measurements. In this letter, we point out practical scenarios in which the assumptions underlying this approach break down, resulting in significant experimental errors. Specific examples for crystalline silicon wafers will be discussed to provide some guidelines on practical limitations of this calibration approach. Large errors are possible for wafers with high surface recombination velocity as might be the case for incoming wafers for a solar cell production line. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

12.
    
In this paper, the gettering potential of phosphorus dopant pastes used in single‐sided screen‐printing processes is investigated including the consequences for essential solar cell parameters. These results are supported by minority carrier lifetime measurements with the quasi‐steady‐state photoconductance method and certified by the analysis of the recombination current density in solar cells on mc‐Si wafers. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

13.
多晶硅太阳电池酸腐表面织构的研究   总被引：1，自引：0，他引：1  
采用酸腐多晶Si片的方法,获得了各向同性的表面织构.酸腐蚀液选取HF-HNO3混合溶液,并用H3PO4进行改良.分别利用扫描电镜(SEM)和光谱响应系统,分析了腐蚀后多晶Si片的表面形貌和反射率.结果表明,酸腐多晶Si表面分布均匀的蚯蚓状腐蚀坑,反射率很低,在等离子增强化学气相沉积(PECVD)Si3N4减反射膜后,反射率大大下降.  相似文献   

14.
    
The determination of the bulk lifetime of bare multicrystalline silicon wafers without the need of surface passivation is a desirable goal. The implementation of an in‐line carrier lifetime analysis is only of benefit if the measurements can be done on bare unprocessed wafers and if the measured effective lifetime is clearly related to the bulk lifetime of the wafer. In this work, we present a detailed experimental study demonstrating the relationship between the effective carrier lifetime of unpassivated wafers and their bulk carrier lifetime. Numerical modelling is used to describe this relationship for different surface conditions taking into account the impact of a saw damage layers with poor electronic quality. Our results show that a prediction of the bulk lifetime from measurements on bare wafers is possible. Based on these results we suggest a simple procedure to implement the analysis for in‐line inspection. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
    
Measuring the bulk lifetime of unpassivated blocks and ingots is of great interest to the solar cell industry. The eddy‐current photoconductance method is a common choice for such measurements, employing the quasi‐steady‐state (QSS) mode for lower lifetime samples, and the transient photoconductance decay (PCD) mode for higher lifetime samples. Due to the high surface recombination velocity in unpassivated bulk samples, the lifetime measured with this method consists of components of recombination at both the surface and in the bulk. In order to determine the bulk lifetime from the measurement data, simulations of both transient and QSS mode measurements were conducted. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

16.
郑兰花  徐进  潘淼  陈朝  史珺 《半导体光电》2012,33(6):830-833,841
研究了冶金法n型多晶硅片磷吸杂、硼吸杂效果及其机理。研究发现,经1 000℃/4h磷吸杂后,硅片平均少子寿命从1.21μs提高到11.98μs;经950℃/1h硼吸杂后,平均少子寿命从1.52μs提升到10.74μs。两种吸杂处理后,硅片电阻率从0.2Ω.cm提高到0.5Ω.cm。结果表明,两种吸杂工艺使得硅片表面形成的重磷、重硼扩散层对金属杂质有较好的吸杂作用,从而减少载流子的复合中心,改善多晶硅片的性能。  相似文献   

17.
对物理冶金法提纯的低成本多晶硅材料进行了磷吸杂实验研究,结果表明,950℃下时吸杂4h去杂效果最好,对磷吸杂机理进行了定性的分析和讨论。把去除吸杂层与制备绒面工艺结合起来,达到较好的效果,节省了太阳电池制备的时间和成本。  相似文献   

18.
    
This paper presents the first conversion efficiency above 20% for a multicrystalline silicon solar cell. The application of wet oxidation for rear surface passivation significantly reduces the process temperature and therefore prevents the degradation of minority‐carrier lifetime. The excellent optical properties of the dielectrically passivated rear surface in combination with a plasma textured front surface result in a superior light trapping and allow the use of substrates below 100 μm thickness. A simplified process scheme with laser‐fired rear contacts leads to conversion efficiencies of 20·3% for multicrystalline and 21·2% for monocrystalline silicon solar cells on small device areas (1 cm2). Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

19.
    
In this study, we investigated the recombination dynamics of minority carriers through the decay profile analysis of transient diffuse reflectance spectroscopy (TDRS) for fresh and potential‐induced degradation (PID) modules. The PID‐affected region in terms of the degradation degree on the modules was firstly localized using conventional methods such as electroluminescence (EL) and lock‐in thermal images. The photogenerated carrier density and carrier lifetime were different in photovoltaic (PV) modules in fresh and PID modes. It was found that the dominant recombination involved the carrier transition via shallow trap states. The distribution of the trap states, however, was extended from the surface to the bulk of the solar cell due to Na ions–decorated defects. The behaviors of the carrier dynamics near the surface and bulk were very different, as inferred from the two different pump wavelengths of 532 and 1064 nm, respectively.  相似文献   

20.
Boron and oxygen contamination in Czochralski‐grown (Cz) silicon leads to a degradation of the minority charge carrier lifetime within short times due to the formation of recombination active complexes. The formation of these complexes is investigated for longer times showing a further development of the defect. This development called ‘regeneration’ is triggered by illumination or applied forward voltages and leads to a new state of the defect. This new state of the defect is proven to be less recombination active allowing higher stable minority carrier lifetimes and conversion efficiencies of solar cells. The influences of temperature and light intensity are discussed. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

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