Download or read book Development of Metal Oxide Thin Films as Carrier Selective Contacts for Silicon Heterojunction Solar Cells written by Ganna Chistiakova and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Transition Metal Oxide as Carrier selective Contacts for Silicon Heterojunction Solar Cells written by and published by . This book was released on 2015 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Reducing light absorption in the non-active solar cell layers, while enabling the extraction of the photogenerated minority carriers at quasi-Fermi levels are two key factors to improve current generation and voltage, and therefore efficiency of silicon heterojunction solar devices. To address these two critical aspects, transition metal oxide materials have been proposed as alternative to the n- and p-type amorphous silicon used as electron and hole selective contacts, respectively. Indeed, transition metal oxides such as molybdenum oxide, titanium oxide, nickel oxide or tungsten oxide combine a wide band gap typically over 3 eV with a band structure and theoretical band alignment with silicon that results in high transparency to the solar spectrum and in selectivity for the transport of only one carrier type. Improving carrier extraction or injection using transition metal oxide has been a topic of investigation in the field of organic solar cells and organic LEDs; from these pioneering works a lot of knowledge has been gained on materials properties, ways to control these during synthesis and deposition, and their impact on device performance. Recently, the transfer of some of this knowledge to silicon solar cells and the successful application of some metal oxide to contact heterojunction devices have gained much attention. In this contribution, we investigate the suitability of various transition metal oxide films (molybdenum oxide, titanium oxide, and tungsten oxide) deposited either by thermal evaporation or sputtering as transparent hole or electron selective transport layer for silicon solar cells. In addition to systematically characterize their optical and structural properties, we use photoemission spectroscopy to relate compound stoichiometry to band structure and characterize band alignment to silicon. The direct silicon/metal oxide interface is further analyzed by quasi-steady state photoconductance decay method to assess the quality of surface passivation. In complement, we construct full device structures incorporating in some cases surface passivation schemes, with measured initial conversion efficiency over 15% and evaluate the carrier transport properties using temperature-dependent current-voltage and capacitance-voltage measurements. With this detailed characterization study, we aim at providing the framework to assess the potential of a material as a carrier selective contact and the understanding of how each of the aforementioned parameters on the metal oxide films influence the full solar cell operating performances.

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 Development of Indium free Thin Films as Contacts for Silicon Heterojunction Solar Cells written by Daniel Meza Arredondo and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Alternative Carrier Selective Materials and Their Application to Heterojunction Solar Cells written by Luis Guillermo Gerling Sarabia and published by . This book was released on 2018 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crystalline silicon (c-Si) solar cells can be considered a highly industrialized and mature product with a record conversion efficiency of 26.6%, not far from the practical limit of 29.4% (for single p/n junction devices). Accordingly, current research and development are addressing some remaining efficiency and cost limitations, including the reduction of (1) carrier recombination in highly doped materials, (2) parasitic absorption by narrow band gap films and (3) high temperature energy-intensive processing (especially critical for wafer thicknesses below 100 μm). In parallel, thin-film PV (e.g. organics and perovskites) have introduced a large number of dopant-free, hole- or electron-selective materials with optoelectronic properties that are comparable or superior to standard p- and n-doped layers in c-Si. Consequently, this thesis work explores novel heterojunctions between c-Si and these carrier-selective contact materials, putting special emphasis on TMO thin films whose wide energy band gap (>3 eV), surface passivation and large work function (>5 eV) characteristics permit their utilization as transparent/passivating/hole-selective front contacts in n-type c-Si (n-Si) solar cells. To this purpose, a comparative study among three thermally evaporated TMOs (V2O5, MoO3 and WO3) allowed correlating their chemical composition with thin film conductivity, optical transmittance, passivation potential and contact resistance on n-Si substrates. The variation of these properties with film thickness, air exposure or temperature annealings was also studied. Overall, V2Ox outperformed the other oxides by obtaining higher implied open-circuit voltages and lower contact resistances, translating into higher selectivities. Next, a thorough study of the TMO/c-Si interface was performed by electron microscopy, secondary ion-mass spectrometry and x-ray photoelectron spectroscopy, identifying two separate contributions to the observed passivation: (1) a chemical component, as evidenced by a thin SiOx interlayer naturally-grown by chemical reaction during TMO evaporation; and (2) a "field-effect" component, a result of a strong inversion (p+) of the n-Si surface, induced by the large work function difference between both materials. Considering all this, an energy band diagram for the TMO/SiOx/n-Si heterojunction was proposed, reflecting the possible physicochemical mechanisms behind c-Si passivation and carrier transport. Then, the characterized TMO/n-Si heterojunctions were implemented as front hole contacts in complete solar cell devices, using thin TMO films (15 nm) contacted by an indium-tin oxide (ITO) anti-reflection/conductive electrode and a silver finger grid. As rear electron contacts, n-type a-SiCx:H thin films (20 nm) were used in localized (laser-doped) and full-area configurations, the former contacted by titanium/aluminum while the latter by ITO/silver electrodes. The best performance solar cells were obtained for V2Ox/n-Si heterojunctions, characterized by an open-circuit voltage (VOC) close to 660 mV and a maximum conversion efficiency of 16.5%. Additional characterization confirmed the good quality of the induced p+/n-Si junction, with ideality factors close to 1 and built-in potentials above 700 mV. Moreover, a photocurrent gain of ̃1 mA/cm2 (300-550 nm wavelength range) was directly attributed to the difference in energy band gaps between TMOs (>2.5 eV) and the a-SiCx:H reference (̃1.7 eV). On a sideline, hole-selective contacts based on PEDOT:PSS polymer solutions were also characterized, resulting in a moderate conversion efficiency of 11.6% in ITO-free devices. Finally, it is worth emphasizing the high degree of innovation in this thesis project, reporting for the first time the properties of these alternative contact materials in the context of c-Si photovoltaics and contributing to a more generic understanding of solar cell operation and design.

Download or read book Heavily Doped Carrier selective Regions for Silicon Solar Cells written by Di Yan and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: While heavily doped regions are an integral part of conventional silicon solar cells for carrier separation and selective transport, they also introduce deleterious effects that constrain their performance. This thesis addresses the fundamental limitations imposed by heavy doping in silicon solar cells and explores the potential of utilising doping in a manner that circumvents them. In particular, selectively doped regions and novel carrier-selective passivating contacts are developed. In heavily doped silicon, energy band gap narrowing (BGN) occurs. Subsequently, the pn product in equilibrium increases, which tends to limit the performance of silicon solar cells. In principle, heavily doped silicon should be analyzed using Fermi-Dirac statistics coupled with a BGN model. Nevertheless, applying Schenk's theoretical BGN model to experimental samples underestimates their corresponding recombination current parameters. Based on a large number of samples and using well-proven models for Auger recombination and carrier mobility, updated empirical expressions for the BGN are derived here for both n-type and p-type silicon. The study confirms that the BGN values in p-type silicon are slightly larger than in n-type silicon. Both updated BGN models contribute to a more complete understanding of the losses and ramifications caused by heavily doped regions in silicon solar cells. A possible approach to reduce the impact of heavily doped regions is to reduce the area they occupy, restricting it to underneath the metal contacts. In this thesis a process to implement such selectively doped (SD) silicon solar cells is developed. The process, based on a controlled etch-back of the diffused region offers the advantage of being self-aligned, which avoids the critical mask alignment step. The TMAH based etch-back solution used here provides a well-controlled etching rate, uniformly etched surface and selectivity to metallic layers (Al or Ag). The poof-of-concept SD silicon solar cells have reached a conversion efficiency of 17.5%. Inspired by silicon heterojunction solar cells and polysilicon emitter BJT, carrier-selective passivating contacts based on heavily doped silicon films are developed. Two approaches of depositing intrinsic polysilicon or amorphous silicon are demonstrated. In both cases, a thermal diffusion process is used to dope and recrystallise the films. The diffusion processes, the intrinsic silicon film thickness, and the interfacial layer conditions are optimized in terms of the trade-off between the recombination current parameter and the contact resistivity. The interfacial layer is found to be critical for blocking the penetration of dopants, for stopping the epitaxial regrowth between the top silicon film and the underlying crystalline silicon, as well as for enhancing the response to a subsequent hydrogenation treatment. Examination of these carrier-selective passivating contact structures before and after the thermal diffusion processes by using XRD, micro-PL and XPS indicates that allowing a moderate level of phosphorus into the silicon oxide and into the silicon substrate is necessary to achieve a low recombination and a low contact resistivity. The electron-selective passivating contacts have been successfully implemented at the rear of n-type silicon solar cells, showing open circuit voltage of > 672 mV and efficiency values up to 20.8%.

Download or read book Atomic Layer Deposition of Metal Oxide Thin Films for Si Heterojunction Solar Cells written by B. Macco and published by . This book was released on 2016 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physics and Technology of Amorphous Crystalline Heterostructure Silicon Solar Cells written by Wilfried G. J. H. M. van Sark and published by Springer Science & Business Media. This book was released on 2011-11-16 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today’s solar cell multi-GW market is dominated by crystalline silicon (c-Si) wafer technology, however new cell concepts are entering the market. One very promising solar cell design to answer these needs is the silicon hetero-junction solar cell, of which the emitter and back surface field are basically produced by a low temperature growth of ultra-thin layers of amorphous silicon. In this design, amorphous silicon (a-Si:H) constitutes both „emitter“ and „base-contact/back surface field“ on both sides of a thin crystalline silicon wafer-base (c-Si) where the electrons and holes are photogenerated; at the same time, a-Si:H passivates the c-Si surface. Recently, cell efficiencies above 23% have been demonstrated for such solar cells. In this book, the editors present an overview of the state-of-the-art in physics and technology of amorphous-crystalline heterostructure silicon solar cells. The heterojunction concept is introduced, processes and resulting properties of the materials used in the cell and their heterointerfaces are discussed and characterization techniques and simulation tools are presented.

Download or read book Advanced Contacts For Crystalline Silicon Solar Cells written by James Bullock and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mainstream dopant-diffused crystalline silicon (c-Si) solar cells have reached a point in their development where losses at the directly-metalized, heavily-doped regions have a significant, and often limiting effect on device performance. The conventional wisdom on addressing this issue is to drastically reduce the percentage of the contacted surface area-to less than 1% in some cases-significantly increasing the complexity of fabrication. An alternative approach is to focus on addressing the losses at the metal / cSi interface by implementing novel 'carrier-selective' contacting structures. This approach to solar cell contacting has the potential to increase the output power whilst significantly simplifying cell architectures and fabrication procedures. This thesis is centered on the conceptual and experimental development of a number of advanced contacting structures for c-Si solar cells, collectively referred to here as 'heterocontacts'. The 'carrier-selectivity' of the contact, that is, how well it collects just one of the two carriers (whilst preserving the other), is used as a universal concept for comparing different contacting strategies, including mainstream contacts based on direct metallization of heavily doped c-Si. To provide a foundation on this topic the initial section of the thesis discusses the concept and theory of carrier-selectivity. This is complemented with an in depth literature review of current state-of-the-art contacting practices for c-Si solar cells. This provides a reference frame with which to compare the three experimental chapters that follow. In the first experimental chapter it is shown that a suitable initial stepping stone towards advancing solar c-Si cell contacts is to combine the benefits of conventional dopant-diffused regions with those of heterocontacts. A number of such hybrid systems are demonstrated and optimized at the contact level through multiple dedicated studies focused on using thin silicon oxide (SiOx), aluminum oxide (AlOx) or hydrogenated amorphous silicon (a-Si:H) passivating interlayers. These interlayers are shown to reduce carrier recombination at the contact surface by up to two orders of magnitude. In a later study we develop and demonstrate a novel a-Si:H enhanced Al / SiOx / c-Si(n+) heterocontact concept. This structure is also explored at the solar cell level, yielding an efficiency of 21% in the initial stages of development - equivalent to that of an analogous cell made with the conventional directly metallized partial contact technique. In the succeeding chapter, the logical next stage in the development of such a concept is explored, that is, to completely remove the heavily doped surface regions, instead using the heterocontacts exclusively to separate electrons and holes. It is demonstrated that this can be achieved using materials with extreme work functions. For the collection of holes, sub-stoichiometric molybdenum oxide MoOx is utilized, favored for its transparency and large work function. Over multiple studies, it is demonstrated that MoOx heterocontact systems, both with and without passivating interlayers can be used to effectively collect holes on both n and p-type c-Si absorbers. This enables its application to a number of novel solar cells architectures, most prominently a novel MoOx partial rear contact cell attaining conversion efficiencies over 20% in the initial proof-ofconcept stage. In the final experimental chapter, a complementary electron heterocontact system is developed, based on a low work function LiFx / Al electrode. This is shown to provide ix excellent electron collection characteristics, both with and without a-Si:H passivating interlayers. The exceptional contact characteristics enabled by this heterocontact allow the demonstration of a first-of-its-kind n-type partial rear contact cell already with an efficiency above 20% in its first demonstration. To conclude the thesis and demonstrate its premise, a novel c-Si cell is developed without the use of dopants. This cell, referred to as the dopant free asymmetric heterocontact (DASH) cell, combines the previously mentioned MoOx based hole contacts and LiFx based electron heterocontacts, both with passivating a-Si:H interlayers. A conversion efficiency of 19.4% is attained for this proof-of-concept device - an improvement by more than 5 percent absolute from the previous DASH cell record and more importantly the first demonstration of such a concept to be competitive with conventional cell designs.

Download or read book Ultrathin Oxide Layers for Solar and Electrocatalytic Systems written by Heinz Frei and published by Royal Society of Chemistry. This book was released on 2022-01-04 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrathin metal oxide layers have emerged in recent years as a powerful approach for substantially enhancing the performance of photo, electro, or thermal catalytic systems for energy, in some cases even enabling the use of highly attractive materials previously found unsuitable. This development is due to the confluence of new synthetic preparation methods for ultrathin oxide layers and a more advanced understanding of interfacial phenomena on the nano and atomic scale. This book brings together the fundamentals and applications of ultrathin oxide layers while highlighting connections and future opportunities with the intent of accelerating the use of these materials and techniques for new and emerging applications of catalysis for energy. It comprehensively covers the state-of-the-art synthetic methods of ultrathin oxide layers, their structural and functional characterization, and the broad range of applications in the field of catalysis for energy. Edited by leaders in the field, and with contributions from global experts, this title will be of interest to graduate students and researchers across materials science and chemistry who are interested in ultrathin oxide layers and their applications in solar energy conversion, renewable energy, photocatalysis, electrocatalysis and protective coatings.

Download or read book High Performance and Low Cost Passivating Carrier selective Contacts for Silicon Photovoltaics written by Jannatul Ferdous Mousumi and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The world is now focusing on expanding renewable energy sources to reduce the carbon footprint and mitigate climate change. Solar energy is one of the most environment-friendly and fastest-growing renewable energy sources in the present world. While crystalline silicon (c-Si) based devices dominate the global photovoltaics (PV) market with a current share of 95%, it is still challenging to achieve the theoretical efficiency limit of 29.4% with this technology due to a few performance limiting factors. Contact recombination losses are dominant among them which result from the recombination of photo-generated charge carriers due to the presence of defects at the metal-semiconductor interface. These losses can be alleviated by inserting thin layers of passivating carrier selective contact (CSC) between c-Si and the overlying metal layer. Over the years different excellent passivating CSC have been developed for c-Si solar cells. In this work, new technologies are explored to improve the performance and reduce the manufacturing costs of the passivating CSC. A very promising passivating CSC for the next generation c-Si solar cell is tunnel oxide passivated doped polycrystalline silicon (poly-Si) contact. In this work, silicon oxide (SiOx) passivated phosphorus-doped poly-Si electron selective contact is developed using an in-line atmospheric pressure chemical vapor deposition process (APCVD) which is simple, low-cost, high-throughput, and well-suited for high-volume manufacturing. Another excellent passivating CSC is hydrogenated doped amorphous silicon (a-Si:H) contact which is widely used to fabricate c-Si heterojunction (SHJ) solar cells. However, this contact degrades if it is annealed at a high temperature (> > 200 C) during metallization. In this work, a novel laser-sintered metal contact printing process is developed which is able to print metal fingers with low bulk resistivity without damaging the a-Si:H contact and excludes the requirement of post-metallization annealing. Along with the fabrication of these passivating CSC different optical, electrical, and materials characterization have been performed to investigate the properties and the performance of the contacts.

Download or read book The Future of Semiconductor Oxides in Next Generation Solar Cells written by Monica Lira-Cantu and published by Elsevier. This book was released on 2017-09-19 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Future of Semiconductor Oxides in Next-Generation Solar Cells begins with several chapters covering the synthesis of semiconductor oxides for NGSCs. Part II goes on to cover the types and applications of NGSCs currently under development, while Part III brings the two together, covering specific processing techniques for NGSC construction. Finally, Part IV discusses the stability of SO solar cells compared to organic solar cells, and the possibilities offered by hybrid technologies. This comprehensive book is an essential reference for all those academics and professionals who require thorough knowledge of recent and future developments in the role of semiconductor oxides in next generation solar cells. Unlocks the potential of advanced semiconductor oxides to transform Next Generation Solar Cell (NGSC) design Full coverage of new developments and recent research make this essential reading for researchers and engineers alike Explains the synthesis and processing of semiconductor oxides with a view to their use in NGSCs

Download or read book Thin Films and Heterostructures for Oxide Electronics written by Satishchandra B. Ogale and published by Springer Science & Business Media. This book was released on 2005-11-21 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxides form a broad subject area of research and technology development which encompasses different disciplines such as materials science, solid state chemistry, physics etc. The aim of this book is to demonstrate the interplay of these fields and to provide an introduction to the techniques and methodologies involving film growth, characterization and device processing. The literature in this field is thus fairly scattered in different research journals covering one or the other aspect of the specific activity. This situation calls for a book that will consolidate this information and thus enable a beginner as well as an expert to get an overall perspective of the field, its foundations, and its projected progress.

Download or read book Thin Film Solar Cells written by Jef Poortmans and published by John Wiley & Sons. This book was released on 2006-10-16 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin-film solar cells are either emerging or about to emerge from the research laboratory to become commercially available devices finding practical various applications. Currently no textbook outlining the basic theoretical background, methods of fabrication and applications currently exist. Thus, this book aims to present for the first time an in-depth overview of this topic covering a broad range of thin-film solar cell technologies including both organic and inorganic materials, presented in a systematic fashion, by the scientific leaders in the respective domains. It covers a broad range of related topics, from physical principles to design, fabrication, characterization, and applications of novel photovoltaic devices.

Download or read book Chemically Deposited Nanocrystalline Metal Oxide Thin Films written by Fabian I. Ezema and published by Springer Nature. This book was released on 2021-06-26 with total page 926 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book guides beginners in the areas of thin film preparation, characterization, and device making, while providing insight into these areas for experts. As chemically deposited metal oxides are currently gaining attention in development of devices such as solar cells, supercapacitors, batteries, sensors, etc., the book illustrates how the chemical deposition route is emerging as a relatively inexpensive, simple, and convenient solution for large area deposition. The advancement in the nanostructured materials for the development of devices is fully discussed.

Download or read book Hole selective Contacts by RF Magnetron Sputtering for Silicon Heterojunction Solar Cell Structures written by Raül Perea Causín and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Research in photovoltaic devices is focusing towards cost-effective technologies to compete with traditional energy sources. In this sense, silicon heterojunction (SHJ) solar cells have excelled owing to their high efficiency and low-temperature processing. Nevertheless, manufacture of conventional SHJ solar cells requires complex deposition systems that involve the use of hazardous gases. Recently, alternative materials have demonstrated good charge-carrier selectivity on silicon. Concretely, oxides of transition metals such as tungsten, molybdenum or vanadium are very effective hole-selective contacts. Furthermore, these materials can be easily deposited by thermal evaporation or sputtering. Several studies have reported successful performance of thermal evaporated transition metal oxides (TMO's) acting as selective contacts. However, a parametrizable deposition technique such as sputtering is more suitable for industrial applications. For this reason, research is needed to be carried out for sputtered TMO's. In this project, molybdenum oxide layers have been deposited by sputtering on crystalline silicon wafers. These layers have been characterized, focusing on composition, structure, and optoelectronic properties. Additionally, solar cell test devices have been fabricated and characterized in order to evaluate the performance of these layers.

Download or read book High Efficiency Silicon Solar Cells written by Martin A. Green and published by Trans Tech Publications Ltd. This book was released on 1987-01-01 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The early chapters comprehensively review the optical and transport properties of silicon. Light trapping is described in detail. Limits on the efficiency of silicon cells are discussed as well as material requirements necessary to approach these limits. The status of current approaches to passifying surfaces, contacts and bulk regions is reviewed. The final section of the book describes the most practical approaches to the fabrication of high-efficiency cells capable of meeting the efficiency targets for both concentrated and non-concentrated sunlight, including a discussion of design and processing approaches for non-crystalline silicon.