Download or read book Investigations Into B o Defect Formation dissociation in Cz silicon and Their Effect on Solar Cell Performance written by Prakash M. Basnyat and published by . This book was released on 2013 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: About 30% of the total market share of industrial manufacture of silicon solar cells is taken by single crystalline Czochralski (CZ) grown wafers. The efficiency of solar cells fabricated on boron-doped Czochralski silicon degrades due to the formation of metastable defects when excess electrons are created by illumination or minority carrier injection during forward bias. The recombination path can be removed by annealing the cell at about 200° C but recombination returns on exposure to light. Several mono-crystalline and multi-crystalline solar cells have been characterized by methods such as laser beam induced current (LBIC), Four-Probe electrical resistivity etc. to better understand the light induced degradation (LID) effect in silicon solar cells. All the measurements are performed as a function of light soaking time. Annealed states are produced by exposing the cells/wafer to temperature above 200° C for 30 minutes and light soaked state was produced by exposure to 1000 W/m2 light using AM1.5 solar simulator for 72 hours. Dark I-V data are analyzed by a software developed at NREL. This study shows that LID, typically, has two components- a bulk component that arises from boron-oxygen defects and a surface component that appears to be due to the SiNx:H-Si interface. With the analysis of dark saturation current (J02), it is seen that the surface LID increases with an increase in the q/2kT component. Results show that cell performance due to bulk effect is fully recovered upon annealing where as surface LID does not recover fully. This statement is also verified by the study of mc- silicon solar cells. Multi-crystalline silicon solar cell has very low oxygen content and, therefore, recombination sites will not be able to form. This shows that there is no bulk degradation in mc- Si solar cells but they exhibit surface degradation. The results suggest that a typical Cz-silicon solar cell with an initial efficiency of - 18% could suffer a reduction in efficiency to - 17.5% after the formation of a metastable defect, out of which - 0.4% comes from a bulk effect and - 0.1 % is linked to a surface effect.

Download or read book On the Performance Limiting Behavior of Defect Clusters in Commercial Silicon Solar Cells written by Bhushan Lal Sopori and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Defect Studies in Cu based P type Transparent Conducting Oxides written by Fnu Ameena and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Among other intrinsic open-volume defects, copper vacancy (VCu) has been theoretically identified as the major acceptor in p-type Cu-based semiconducting transparent oxides, which has potential as low-cost photovoltaic absorbers in semi-transparent solar cells. A series of positron annihilation experiments with pure Cu, Cu2O, and CuO presented strong presence of VCu and its complexes in the copper oxides. The lifetime data also showed that the density of VCu was becoming higher as the oxidation state of Cu increased which was consistent with the decrease in the formation energy of VCu. Doppler broadening measurements further indicated that electrons with low momentum made more contribution to the contributed as pure Cu oxidizes to copper oxides. The metastable defects are known to be generated in Cu2O upon illumination and it has been known to affect the performance of Cu2O-based hetero-junctions used in solar cells. The metastable effect was studied using positron annihilation lifetime spectroscopy and its data showed the change in the defect population upon light exposure and the minimal effect of lightinduced electron density increase in the bulk of materials to the average lifetime of the positrons. The change in the defect population is concluded to be related to the dissociation and association of VCu - VCu complexes. For example, the shorter lifetime under light was ascribed to the annihilation with smaller size vacancies, which explains the dissociation of the complexes with light illumination. Doppler broadening of the annihilation was independent of light illumination, which suggested that the chemical nature of the defects remained without change upon their dissociation and association - only the size distribution of copper vacancies varied. The delafossite metal oxides, CuMIIIO2 are emerging wide-bandgap p-type semiconductors. In this research, the formation energies of structural vacancies are calculated using Van Vechten cavity model as an attempt to study the effect of the size of the MIII cation in the delafossites starting from Cu2O. Comparison of the formation energies between Cu2O and delafossite oxides clearly showed that the equilibrium concentration of the vacancies depended strongly on the structural parameters varied by the presence of different MIII cations. In particular, the size of the MIII cation greatly influenced the defect formation energies of VCu. It was observed from our calculations, as the size increases the formation energy decreases.

Download or read book Efficiency limiting Defects in Polycrystalline Silicon Solar Cell Material Revealed by Iron Precipitation Kinetics written by Robert Jeffrey Bailey and published by . This book was released on 1993 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Formation of Defect Clusters in Mc Silicon Solar Cells written by Dietmar Kohler and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Photovoltaic Silicon written by Deren Yang and published by Springer. This book was released on 2019-11-28 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The utilization of sun light is one of the hottest topics in sustainable energy research. To efficiently convert sun power into a reliable energy – electricity – for consumption and storage, silicon and its derivatives have been widely studied and applied in solar cell systems. This handbook covers the photovoltaics of silicon materials and devices, providing a comprehensive summary of the state of the art of photovoltaic silicon sciences and technologies. This work is divided into various areas including but not limited to fundamental principles, design methodologies, wafering techniques/fabrications, characterizations, applications, current research trends and challenges. It offers the most updated and self-explanatory reference to all levels of students and acts as a quick reference to the experts from the fields of chemistry, material science, physics, chemical engineering, electrical engineering, solar energy, etc..

Download or read book Heavily N Type Doped Silicon and the Dislocation Formation During Its Growth by the Czochralski Method written by Ludwig Stockmeier and published by Fraunhofer Verlag. This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavily doped silicon is required for devices such as PowerMOSFETs. For the devices to be as sufficient as possible it is necessary to lower the electrical resistivity of the silicon substrate as low as possible. Yet, during the growth of heavily n-type doped silicon by the Czochralski method dislocation formation occurs frequently, reducing yield. Thus this work covers the topics intrinsic point defects, electrical activity of dopant atoms, spreading of dislocations and facet growth. Each topic is discussed in regard of their possible impact on the formation of the dislocations. In doing so, the control of facet growth is found to be most crucial to prevent the formation of the dislocations.

Download or read book Government Reports Announcements Index written by and published by . This book was released on 1995 with total page 1396 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impact of Dopant Compensation on the Electrical Properties of Silicon for Solar Cells Applications written by Fiacre Emile Rougieux and published by . This book was released on 2012 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis aims at understanding the mechanisms limiting the efficiency of compensated silicon solar cells (containing boron and phosphorus in the bulk). Such dopant compensation is common in solar grade materials, especially in silicon from the metallurgical route, and can potentially lead to a degradation of the materials electronic properties. We experimentally show that a thermal oxidation can create an n-type layer at the surface of compensated p-type silicon. This n-type layer is further shown to interfere with device performance and material characterization. We investigate the impact of compensation on the minority carrier lifetime, in particular for recombination through defects. Metastable defects such as chromium-boron pairs and the boron-oxygen defect are shown to degrade the lifetime of compensated n-type silicon. The boron-oxygen defect in compensated n-type silicon is then experimentally investigated. It is shown that if not mitigated, the boron-oxygen defect leads to a strong reduction in implied VOC. The defect is also shown to be fundamentally different in compensated n-type silicon compared to p-type silicon. Its concentration does not depend on the net doping and its recombination activity is dominated by a shallow defect rather than a deep defect. Through a theoretical investigation, we show that the carrier mobility is also affected by compensation. Both theory and experiments confirm that the mobility is reduced by the combined presence of acceptors and donors. Compensation not only increases the amount of ionized impurities and decreases the amount of free carriers, it also affects the scattering cross section of ionized impurities and free carriers. Theoretical calculations show a relatively weak influence of the compensating impurities on the mobility. However experimental results suggest a stronger influence of compensating impurities. This results in mobilities slightly lower than predicted by advanced model such as Klaassen's model. A new method to measure the sum of the majority and minority carrier mobility in silicon is introduced. Measurement of the influence of dopant density, injected carriers and temperature on the mobility sum are made and compared to data available in the literature. -- provided by Candidate.

Download or read book Addressing Optical Recombination and Resistive Losses in Crystalline Silicon Solar Cells written by Thomas Gerald Allen and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of any photovoltaic device is determined by its ability to mitigate optical, recombination, and resistive energy losses. This thesis investigates new materials and nascent technologies to address these energy loss mechanisms in crystalline silicon solar cells. Optical losses, specifically the suppression of energy losses resulting from front surface reflection, are first analysed. The use of reactive ion etched black silicon texturing, a nano-scale surface texture, is assessed with respect to the two conventional texturing processes: isotexture and random pyramids. While nano-scale surface textures offer a means of almost eliminating front surface reflection, relatively poor internal optical properties (i.e. light trapping) compared to both conventional textures can compromise any optical gains realised on the front surface. It is also shown that enhanced recombination losses remains a barrier to the application of black silicon texturing to further improve high performance devices, though this will likely have less of an impact on multi-crystalline silicon cells where bulk recombination dominates.The suppression of recombination losses at surface defects by gallium oxide (Ga2O3), an alternative to aluminium oxide (Al2O3), is also investigated. It is demonstrated that, as in Al2O3, thin films of amorphous Ga2O3 can passivate surface defects through a direct reduction of recombination active defects and via the establishment of a high negative charge density. Further investigations demonstrate that Ga2O3 is applicable to random pyramid surfaces textures, and is compatible with plasma enhanced chemical vapour deposited silicon nitride (SiNx) capping for anti-reflection purposes. Indeed, the Ga2O3 / SiNx stack is shown to result in enhanced thermal stability and surface passivation properties comparable to state-of-the-art Al2O3 films. In addition, it is also shown that Ga2O3 can act as a Ga source in a laser doping process, as demonstrated by a proof-of-concept p-type laser doped partial rear contact solar cell with an efficiency of 19.2%. Finally, the resistive losses associated with metal / silicon contacts are addressed. It is demonstrated that a significant asymmetry in the work function of the electron and hole contact materials is sufficient to induce carrier selectivity without the need for heavy doping. This had recently been demonstrated for hole contacts with the high work function material molybdenum oxide. In this thesis specific attention is given to finding a suitable low work function material for the electron contact. Calcium, a common low work function electrode in organic electronic devices, is shown to act as a low resistance Ohmic contact to crystalline silicon without the need for heavy doping. Fabrication of n-type solar cells with partial rear calcium contacts resulted in a device efficiency of 20.3%, limited largely by recombination at the Ca / Si interface. This limitation to device efficiency is shown to be partially alleviated by the application of a passivating titania (TiOx) interlayer into the cell structure, resulting in an increase in device efficiency to 21.8% -- the highest reported efficiency for a TiOx-based heterojunction solar cell to date.

Download or read book Silicon Heterojunction Solar Cells written by W.R. Fahrner and published by Trans Tech Publications Ltd. This book was released on 2006-08-15 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The world of today must face up to two contradictory energy problems: on the one hand, there is the sharply growing consumer demand in countries such as China and India. On the other hand, natural resources are dwindling. Moreover, many of those countries which still possess substantial gas and oil supplies are politically unstable. As a result, renewable natural energy sources have received great attention. Among these, solar-cell technology is one of the most promising candidates. However, there still remains the problem of the manufacturing costs of such cells. Many attempts have been made to reduce the production costs of “conventional” solar cells (manufactured from monocrystalline silicon using diffusion methods) by instead using cheaper grades of silicon, and simpler pn-junction fabrication. That is the ‘hero’ of this book; the heterojunction solar cell.

Download or read book Loss Analysis of Crystalline Silicon Solar Cells using Photoconductance and Quantum Efficiency Measurements written by and published by Cuvillier Verlag. This book was released on 2003-08-19 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Origin and Formation of Large Defect Clusters in Multicrystalline Silicon Solar Cells written by Dietmar Kohler and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Surface Passivation Effects on Thin Crystalline Silicon Solar Cell Performance written by Yibin Bai and published by . This book was released on 1996 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A New Approach to Prevent the Negative Impact of the Metastable Defect in Boron Doped CZ Silicon Solar Cells written by Axel Herguth and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Back Surface Cell Structures for Reducing Recombination in CZ Silicon Solar Cells written by and published by . This book was released on 1994 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mass-produced terrestrial CZ silicon solar cells are currently entering the domain in which bulk diffusion length is comparable to the cell thickness, so that recombination at the back surface can have a significant effect on device performance. Three manufacturable processes that address the problem of back recombination are examined here: boron diffusion from a deposited doped SiO2, layer; Al-alloyed layers using screen-printed paste; and use of a collecting n* layer on the back interdigitated with the positive electrode. 104-cm2 cells fabricated at Siemens Solar Industries using these back surface structures are characterized by current-voltage, spectral response, photoconductivity decay, and SIMS measurements.

Download or read book Lifetime Spectroscopy written by Stefan Rein and published by Springer Science & Business Media. This book was released on 2005-11-25 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lifetime spectroscopy is one of the most sensitive diagnostic tools for the identification and analysis of impurities in semiconductors. Since it is based on the recombination process, it provides insight into precisely those defects that are relevant to semiconductor devices such as solar cells. This book introduces a transparent modeling procedure that allows a detailed theoretical evaluation of the spectroscopic potential of the different lifetime spectroscopic techniques. The various theoretical predictions are verified experimentally with the context of a comprehensive study on different metal impurities. The quality and consistency of the spectroscopic results, as explained here, confirms the excellent performance of lifetime spectroscopy.