Download or read book Titanium oxide based Electron selective Contacts to Crystalline Silicon Characterization and Application to Solar Cells written by Valeriya Titova and published by . This book was released on 2021 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 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 Optimization of Electron Selective Contacts for Silicon Solar Cells written by Arnau Torrens Dinarès and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, one of the most urgent and important problems that humankind has to face is climate change and global warming. One way to approach it, is by changing the way energy is produced from non-renewable sources, such as coal or gas, to renewable sources, like wind or solar power. In this report, the focus is set on solar energy and how to improve the efficiency of photovoltaic solar cells. Titanium nitride (TiNx) is studied as an electron selective contact to possibly substitute magnesium-aluminium (Mg/Al). Several experiments were carried out changing the sputtering deposition conditions such as the concentration of N2 gas used during the deposition or the deposition time. However, the results obtained were not satisfactory enough. A new material, ITO (Indium Tin Oxide) on an electron doped substrate (n+), was also tested and positive results were yielded. A contact resistivity of approximately ?c = 80 m?cm2 was achieved.
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 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 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 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 Development And Interface Surface Characterization Of Titanium Dioxide And Zinc Oxide Electron Collection Interlayer Materials For Organic Solar Cells written by Kai-Lin Ou and published by . This book was released on 2014 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Improving the Performance and Durability of Metal Contacts in Crystalline Silicon Solar Cells Using Advanced Characterization written by Nafis Iqbal and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar energy is one of the fastest growing forms of energy generation due to its low cost, lack of emissions, minimal maintenance, and excellent durability. However, like any other technology, it is also not free from defects and degradation, which limit its performance in the real world. Most of the degradation is related to metal contacts, which also happens to be one of the most expensive items in manufacturing, comprising almost half of the cost of converting a silicon wafer into a photovoltaic (PV) cell. Therefore, studying contact degradation to make them reliable and free of defects is the key to achieving high energy yields. High efficiency PV modules that are both cheap and reliable with an extended lifetime ultimately reduce the levelized cost of energy. This study aims to characterize contact degradation in solar cells to identify the root causes of performance losses and develop alternate solutions to metallization. Electrical and optical characterizations were performed on both accelerated aged and field exposed solar cells and modules to look for specific performance losses. Furthermore, materials characterization was performed on selected samples to understand the potential root causes and factors affecting the degradation. Unencapsulated solar cells mainly consisting of newer cell technologies and metallization were exposed to acetic acid to simulate field conditions and understand the effect on contact corrosion. Finally, a low-cost novel contact technology called the "transferred foil contact" was developed that can be used as the back contact of a highly efficient silicon heterojunction solar cell, to minimize recombination, and potentially combine cell metallization and interconnection. An overview of the solar energy history and current state-of-the-art is first discussed, followed by a chapter on solar cell device physics and contact technology. The following chapters discuss the different degradation mechanisms in terms of the process-structure-properties relationships of the PV materials. iii
Download or read book Novel Uses of Titanium Dioxide for Silicon Solar Cells written by Bryce Sydney Richards and published by . This book was released on 2002-10-01 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization and Modeling of Contacting Crystalline Silicon Solar Cells written by Stefan Kontermann and published by . This book was released on 2009 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Organic Selective Contacts for Crystalline Silicon Solar Cells written by Marc-Uwe Halbich and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transparent Passivating Contacts for Front Side Application in Crystalline Silicon Solar Cells written by Josua Andreas Stückelberger and published by . This book was released on 2018 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'auteur: Solar energy ; photovoltaics ; crystalline ; silicon ; passivation ; mixed-phase ; poly-Si ; selective ; oxide ; fluorine.
Download or read book Semiconductor Materials for Solar Photovoltaic Cells written by M. Parans Paranthaman and published by Springer. This book was released on 2015-09-16 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the current status of semiconductor materials for conversion of sunlight to electricity, and highlights advances in both basic science and manufacturing. Photovoltaic (PV) solar electric technology will be a significant contributor to world energy supplies when reliable, efficient PV power products are manufactured in large volumes at low cost. Expert chapters cover the full range of semiconductor materials for solar-to-electricity conversion, from crystalline silicon and amorphous silicon to cadmium telluride, copper indium gallium sulfide selenides, dye sensitized solar cells, organic solar cells, and environmentally friendly copper zinc tin sulfide selenides. The latest methods for synthesis and characterization of solar cell materials are described, together with techniques for measuring solar cell efficiency. Semiconductor Materials for Solar Photovoltaic Cells presents the current state of the art as well as key details about future strategies to increase the efficiency and reduce costs, with particular focus on how to reduce the gap between laboratory scale efficiency and commercial module efficiency. This book will aid materials scientists and engineers in identifying research priorities to fulfill energy needs, and will also enable researchers to understand novel semiconductor materials that are emerging in the solar market. This integrated approach also gives science and engineering students a sense of the excitement and relevance of materials science in the development of novel semiconductor materials. · Provides a comprehensive introduction to solar PV cell materials · Reviews current and future status of solar cells with respect to cost and efficiency · Covers the full range of solar cell materials, from silicon and thin films to dye sensitized and organic solar cells · Offers an in-depth account of the semiconductor material strategies and directions for further research · Features detailed tables on the world leaders in efficiency demonstrations · Edited by scientists with experience in both research and industry
Download or read book Fabrication and Characterization of Functional ALD Metal Oxide Thin Films for Solar Applications written by Ludmilla Steier and published by . This book was released on 2016 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'autrice: photoelectrochemical water oxidation ; hematite ; ultrasonic spray pyrolysis ; atomic layer deposition (ALD) ; host-guest approach ; electrochemical impedance spectroscopy ; trap states ; interfacial functional layers ; electron selective contacts ; hybrid organic-inorganic perovskite solar cells.
