Download or read book Non vacuum Deposition of Cu In Ga Se2 Absorber Layers for Thin Film Solar Cells written by Alexander Roland Uhl and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of Non vacuum and Low cost Techniques for Cu In Ga Se S 2 Thin Film Solar Cell Processing written by Christopher J. Hibberd and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar photovoltaic modules provide clean electricity from sunlight but will not be able tocompete on an open market until the cost of the electricity they produce is comparable to thatproduced by traditional methods. At present, modules based on crystalline silicon wafer solarcells account for nearly 90% of photovoltaic production capacity. However, it is anticipatedthat the ultimate cost reduction achievable for crystalline silicon solar cell production will besomewhat limited and that thin film solar cells may offer a cheaper alternative in the longterm. The highest energy conversion efficiencies reported for thin film solar cells have beenfor devices based around chalcopyrite Cu(In, Ga)(Se, S)2 photovoltaic absorbers. The most efficient Cu(In, Ga)(Se, S)2 solar cells contain absorber layers deposited by vacuumco-evaporation of the elements. However, the cost of ownership of large area vacuumevaporation technology is high and may be a limiting factor in the cost reductions achievablefor Cu(In, Ga)(Se, S)2 based solar cells. Therefore, many alternative deposition methods areunder investigation. Despite almost thirty companies being in the process of commercialisingthese technologies there is no consensus as to which deposition method will lead to the mostcost effective product. Non-vacuum deposition techniques involving powders and chemical solutions potentiallyoffer significant reductions in the cost of Cu(In, Ga)(Se, S)2 absorber layer deposition ascompared to their vacuum counterparts. A wide range of such approaches has beeninvestigated for thirty years and the gap between the world record Cu(In, Ga)(Se, S)2 solarcell and the best devices containing non-vacuum deposited absorber layers has closedsignificantly in recent years. Nevertheless, no one technique has demonstrated its superiorityand the best results are still achieved with some of the most complex approaches. The work presented here involved the development and investigation of a new process forperforming one of the stages of non-vacuum deposition of Cu(In, Ga)(Se, S)2 absorber layers. The new process incorporates copper into an initial Group III-VI precursor layer, e.g. indiumgallium selenide, through an ion exchange reaction performed in solution. The ion exchangereaction requires only very simple, low-cost equipment and proceeds at temperatures over1000?C lower than required for the evaporation of Cu under vacuum. In the new process, indium (gallium) selenide initial precursor layers are immersed insolutions containing Cu ions. During immersion an exchange reaction occurs and Cu ionsfrom the solution exchange places with Group III ions in the layer. This leads to theformation of an intimately bonded, laterally homogeneous copper selenide? indium (gallium)selenide modified precursor layer with the same morphology as the initial precursor. These modified precursor layers were converted to single phase chalcopyrite CuInSe2 andCu(In, Ga)Se2 by annealing with Se in a tube furnace system. Investigation of the annealingtreatment revealed that a series of phase transformations, beginning at low temperature, leadto chalcopyrite formation. Control of the timing of the Se supply was demonstrated toprevent reactions that were deemed detrimental to the morphology of the resultingchalcopyrite layers. When vacuum evaporated indium (gallium) selenide layers were used asinitial precursors, solar cells produced from the absorber layers exhibited energy conversionefficiencies of up to 4%. While these results are considered promising, the devices werecharacterised by very low open circuit voltages and parallel resistances. Rapid thermal processing was applied to the modified precursor layers in an attempt tofurther improve their conversion into chalcopyrite material. Despite only a small number ofsolar cells being fabricated using rapid thermal processing, improvements in open circuitvoltage of close to 150mV were achieved. However, due to increases in series resistance andreductions in current collection only small increases in solar cell efficiency were recorded. Rapid thermal processing was also used to demonstrate synthesis of single phase CuInS2from modified precursor layers based on non-vacuum deposited indium sulphide. Non-vacuum deposition methods provide many opportunities for the incorporation ofundesirable impurities into the deposited layers. Analysis of the precursor layers developedduring this work revealed that alkali atoms from the complexant used in the ion exchangebaths are incorporated into the precursor layers alongside the Cu. Alkali atoms exhibitpronounced electronic and structural effects on Cu(In, Ga)Se2 layers and are beneficial in lowconcentrations. However, excess alkali atoms are detrimental to Cu(In, Ga)Se2 solar cellperformance and the problems encountered with cells produced here are consistent with theeffects reported in the literature for excess alkali incorporation. It is therefore expected thatfurther improvements in solar cell efficiency might be achieved following reformulation ofthe ion exchange bath chemistry.

Download or read book Cu In1 xGax Se2 Based Thin Film Solar Cells written by Subba Ramaiah Kodigala and published by Academic Press. This book was released on 2011-01-03 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cu(In1-xGax)Se2 Based Thin Film Solar Cells provides valuable contents about the fabrication and characterization of chalcopyrite Cu(In1-xGax)Se2 based thin film solar cells and modules. The growth of chalcopyrite Cu(In1-xGax)(S1-ySey)2 absorbers, buffers, window layers, antireflection coatings, and finally metallic grids, which are the sole components of solar cells, is clearly illustrated. The absorber, which contains multiple elements, segregates secondary phases if the growth conditions are not well optimized i.e., the main drawback in the fabrication of solar cells. More importantly the solutions for the growth of thin films are given in detail. The properties of all the individual layers and single crystals including solar cells analyzed by different characterization techniques such as SEM, AFM, XPS, AES, TEM, XRD, optical, photoluminescence, and Raman spectroscopy are explicitly demonstrated. The electrical analyses such as conductivities, Hall mobilities, deep level transient spectroscopy measurements etc., provide a broad picture to understand thin films or single crystals and their solar cells. The book clearly explains the working principle of energy conversion from solar to electrical with basic sciences for the chalcopyrite based thin film solar cells. Also, it demonstrates important criteria on how to enhance efficiency of the solar cells and modules. The effect of environmental factors such as temperature, humidity, aging etc., on the devices is mentioned by citing several examples. - Illustrates a number of growth techniques to prepare thin film layers for solar cells - Discusses characterization techniques such as XRD, TEM, XPS, AFM, SEM, PL, CL, Optical measurements, and Electrical measurements - Includes I-V, C-V measurements illustrations - Provides analysis of solar cell efficiency - Presents current trends in thin film solar cells research and marketing

Download or read book Electron Selective TiO2 Contact for Cu In Ga Se2 Solar Cells written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The non-toxic and wide bandgap material TiO2 is explored as an n-type buffer layer on p-type Cu(In, Ga)Se2 (CIGS) absorber layer for thin film solar cells. The amorphous TiO2 thin film deposited by atomic layer deposition process at low temperatures shows conformal coverage on the CIGS absorber layer. Solar cells from non-vacuum deposited CIGS absorbers with TiO2 buffer layer result in a high short-circuit current density of 38.9 mA/cm2 as compared to 36.9 mA/cm2 measured in the reference cell with CdS buffer layer, without compromising open-circuit voltage. The significant photocurrent gain, mainly in the UV part of the spectrum, can be attributed to the low parasitic absorption loss in the ultrathin TiO2 layer (~10 nm) with a larger bandgap of 3.4 eV compared to 2.4 eV of the traditionally used CdS. Overall the solar cell conversion efficiency was improved from 9.5% to 9.9% by substituting the CdS by TiO2 on an active cell area of 10.5 mm2. In conclusion, optimized TiO2/CIGS solar cells show excellent long-term stability. The results imply that TiO2 is a promising buffer layer material for CIGS solar cells, avoiding the toxic CdS buffer layer with added performance advantage.

Download or read book New Deposition Process of Cu In Ga Se2 Thin Films for Solar Cell Applications written by Himal Khatri and published by . This book was released on 2009 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molybdenum (Mo) is currently the most common material used for Cu(In, Ga)Se2 solar cell back contacts. The first objective of this study is to utilize in-situ and ex-situ characterization techniques to investigate the growth, as well as the physical and chemical properties, of Mo thin films deposited by RF magnetron sputtering onto soda-lime glass (SLG) substrates. The effects of the deposition pressure on the nucleation and growth mechanisms that ultimately influence morphology and grain structure have been studied. Correspondence between real time spectroscopic ellipsometry (RTSE), X-ray diffraction (XRD), atomic force microscopy (AFM), and four-point probe resistivity measurements indicate that increasing deposition pressure leads to smaller average grain sizes and higher oxygen content in the Mo thin films. Changes of the material properties were also evaluated by changing RF power. It is observed that higher RF power, results in higher conductivity films. The second and overall objective of this work is to focus on the deposition and characterization of the Cu(In, Ga)Se2 absorber layer using the hybrid co-sputtering and evaporation process, which has potential for commercial PV. Solar cells were completed with a range of elemental compositions in the absorber layer, keeping a constant profile of Ga and varying Cu concentrations. The slightly Cu deficient Cu(In, Ga)Se2 films of band gap ~1.15 eV fabricated by this process consist of a single chalcopyrite phase and device efficiencies up to 12.4% were achieved for the composition ratios (x, y) = (0.30, 0.88). Correspondence between energy dispersive X-ray spectroscopy (EDS), X-ray diffraction, transmission and reflection (T & R), four-point probe resistivity, and current density-voltage (J-V) measurements indicate that increased Cu concentration leads to the incorporation of a secondary phase Cu2-xSe compound in the Cu(In, Ga)Se2 films, which is detrimental to cell performance. The third objective of this work is to evaluate the Cu2-xSe material properties by employing in-situ RTSE, as well as ex-situ SE and various other characterization techniques. SE revealed that the dielectric function spectra of Cu2-xSe evolve with temperature, providing insights into the evolution of transport properties and critical point structures. At room temperature, semi-metallic behavior of Cu2-xSe thin films was revealed by SE and Hall Effect measurements. These characteristics serve as key inputs for optical modeling of complex layer structures of Cu(In, Ga)Se2 films grown by 2- and 3-step processes.

Download or read book Wide Gap Chalcopyrites written by Susanne Siebentritt and published by Springer Science & Business Media. This book was released on 2006-02-25 with total page 267 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chalcopyrites, in particular those with a wide band gap, are fascinating materials in terms of their technological potential in the next generation of thin-film solar cells and in terms of their basic material properties. They exhibit uniquely low defect formation energies, leading to unusual doping and phase behavior and to extremely benign grain boundaries. This book collects articles on a number of those basic material properties of wide-gap chalcopyrites, comparing them to their low-gap cousins. They explore the doping of the materials, the electronic structure and the transport through interfaces and grain boundaries, the formation of the electric field in a solar cell, the mechanisms and suppression of recombination, the role of inhomogeneities, and the technological role of wide-gap chalcopyrites.

Download or read book Alternative Buffer Layer Development in Cu In Ga Se2 Thin Film Solar Cells written by Peipei Xin and published by . This book was released on 2017 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cu(In,Ga)Se2-based thin film solar cells are considered to be one of the most promising photovoltaic technologies. Cu(In,Ga)Se2 (CIGS) solar devices have the potential advantage of low-cost, fast fabrication by using semiconductor layers of only a few micrometers thick and high efficiency photovoltaics have been reported at both the cell and the module levels. CdS via chemical bath deposition (CBD) has been the most widely used buffer option to form the critical junction in CIGS-based thin film photovoltaic devices. However, the disadvantages of CdS can’t be ignored - regulations on cadmium usage are getting stricter primarily due to its toxicity and environmental impacts, and the proper handling of the large amount of toxic chemical bath waste is a massive and expensive task. ☐ This dissertation is devoted to the development of Cd-free alternative buffer layers in CIGS-based thin film solar cells. Based on the considerations of buffer layer selection criteria and extensive literature review, Zn-compound buffer materials are chosen as the primary investigation candidates. Radio frequency magnetron sputtering is the preferred buffer deposition approach since it’s a clean and more controllable technique compared to CBD, and is readily scaled to large area manufacturing. ☐ First, a comprehensive study of the ZnSe1-xOx compound prepared by reactive sputtering was completed. As the oxygen content in the reactive sputtering gas increased, ZnSe1-xOx crystallinity and bandgap decreased. It’s observed that oxygen miscibility in ZnSe was low and a secondary phase formed when the O2 / (O2 + Ar) ratio in the sputtering gas exceeded 2%. Two approaches were proposed to optimize the band alignment between the CIGS and buffer layer. One method focused on the bandgap engineering of the absorber, the other focused on the band structure modification of the buffer. As a result, improved current of the solar cell was achieved although a carrier transport barrier at the junction interface still limited the device performance. ☐ Second, an investigation of Zn(S,O) buffer layers was completed. Zn(S,O) films were sputtered in Ar using a ZnO0.7S0.3 compound target. Zn(S,O) films had the composition close to the target with S / (S+O) ratio around 0.3. Zn(S,O) films showed the wurtzite structure with the bandgap about 3.2eV. The champion Cu(In,Ga)Se2 / Zn(S,O) cell had 12.5% efficiency and an (Ag,Cu)(In,Ga)Se2 / Zn(S,O) cell achieved 13.2% efficiency. Detailed device analysis was used to study the Cu(In,Ga)Se2 and (Ag,Cu)(In,Ga)Se2 absorbers, the influence of absorber surface treatments, the effects of device treatments, the sputtering damage and the Na concentration in the absorber. ☐ Finally alternative buffer layer development was applied to an innovative superstrate CIGS configuration. The superstrate structure has potential benefits of improved window layer properties, cost reduction, and the possibility to implement back reflector engineering techniques. The application of three buffer layer options – CdS, ZnO and ZnSe was studied and limitations of each were characterized. The best device achieved 8.6% efficiency with a ZnO buffer. GaxOy formation at the junction interface was the main limiting factor of this device performance. For CdS / CIGS and ZnSe / CIGS superstrate devices extensive inter-diffusion between the absorber and buffer layer under CIGS growth conditions was the critical problem. Inter-diffusion severely deteriorated the junction quality and led to poorly behaved devices, despite different efforts to optimize the fabrication process.

Download or read book Investigations of the Reactive Co sputtering Deposition of Cu In 1 x Ga X S 1 y Se Y 2 Absorber Layers for Thin Film Solar Cells written by and published by . This book was released on 2014 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Enhancement of the Deposition Processes of Cu In Ga Se2 and Cds Thin Films Via In situ and Ex situ Measurements for Solar Cell Application written by Vikash Ranjan and published by . This book was released on 2011 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin films of Cu(In, Ga)Se2 deposited by 1-stage, 2-stage and 3-stage co-evaporation processes result into the highest efficiency solar cells. Controlling the rate and sequences of individual sources during these co-evaporation processes are important for better quality Cu(In, Ga)Se2 absorber layers. At the same time, spectroscopic ellipsometry due to its ex-situ as well as in-situ application is considered as a very powerful tool to understand the material properties as well as to monitor the process. Nevertheless, spectroscopic ellipsometry was not properly utilized until now to characterize Cu(In, Ga)Se2 thin films. In this study, one of our goal is to understand the optical and electrical properties of Cu(In, Ga)Se2 as a function of process and composition. In the first part of this study, we implemented ex-situ spectroscopic ellipsometry (SE) along with other characterization techniques like Secondary ion mass spectroscopy (SIMS), Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), x-ray diffraction (XRD), atomic force microscopy (AFM) etc. to compare Cu(In, Ga)Se2 thin films deposited by the above mentioned three co-evaporation processes. During this study, we were able to use SE to find the thickness, roughness, band gap, Ga grading of the Cu(In, Ga)Se2 deposited by 2-stage and 3-stage process. Finding of SE were correlated by SIMS, AES, SEM etc. In the case of Cu(In, Ga)Se2 deposited by 1-stage process, due to the high surface roughness, we are not able to implement the ex-situ spectroscopic ellipsometry. In the second and third part of this study, real time spectroscopic ellipsometry is implemented to study the material properties of Cu(In, Ga)Se2 thin films as a function of Cu and Ga concentration. Effectively, in a 3-stage co-evaporation process, the composition of the film changes during the process. To monitor and control the composition of Cu(In, Ga)Se2 during the 3-stage process by in-situ ellipsometry, it was necessary to understand the optical properties of Cu(In, Ga)Se2 as a function of Cu atomic percentage (at.%) as well as Ga at.%. Along with this, the inability to implement ex-situ SE for Cu(In, Ga)Se2 thin film motivated us to implement the spectroscopic ellipsometry in real time i.e. during the growth of the film. This in-situ real time application of SE helped us in understanding the micostructural evolution and dependence of the band gap with the Cu atomic percentage (at.%) as well as the Ga at.%. We also used this opportunity to understand the shift in the critical points as a function of temperature for CuInSe2 alloys. Characterization like AES, XRD, AFM etc were performed after the growth at room temperature to corroborate the RTSE findings. In the fourth and last part of this study, the growth of CdS on a Cu(In, Ga)Se2 surface as a function of time was studied using SE as well as AFM. We also used this opportunity to compare the growth of CdS on another substrate (SiO2). Spectroscopic ellipsometry and AFM revealed a quantum confinement effect in the case of CdS on SiO2 whereas no such effect was observed for CdS on Cu(In, Ga)Se2 surface due to the growth of compact CdS layers.

Download or read book Air light Exposure of Cu In Ga Se2 Thin Film Absorber Layers and the Effects on Complete Solar Cells written by Torsten Hölscher and published by . This book was released on 2022* with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis deals with the modification of the Cu(In,Ga)Se2 surface, caused by illumination in ambient air. After the specifically exposure of the bare CIGSe surface to air and light (air-light exposure = ALE), the absorber layers have been investigated with time-resolved photoluminescence (TRPL) and X-ray photoelectron spectroscopy (XPS). Solar cells with ALE absorbers have been diagnosed to be limited by recombination at the Absorber/Buffer interface, using voltage dependent admittance spectroscopy and measuring the open circuit voltage as a function of temperature VOC(T) as well as a function of time VOC(t).

Download or read book High efficiency Cu In Ga Se2 Thin Film Solar Cells Without Intermediate Buffer Layers written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Heat Treatments and Reduced Absorber Layer Thickness on Cu in Ga se2 Thin Film Solar Cells written by Vinodh Chandrasekaran and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The thickness of the Molybdenum back contact layer was increased to see if the amount of Sodium from the substrate had any effect on the device performance. The Ga/In ratio was altered and its effect was also studied. The 0.65um thick devices showed a large reduction in Voc̕s and Jsc̕s. The effect of Selenization time and Selenium flux during Selenization were studied at each of the different thicknesses.

Download or read book Growing Cu In Ga Se2 Thin Film Solar Cells with High Efficiency and Low Production Costs written by Shihang Yang and published by . This book was released on 2012 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two major approaches are performed to improve solar cell performances. Light trapping by etching AZO top contact for creating pyramid-structures to enhance light scattering. Efficiency is increased by more than 1.5% for solar cells with etched AZO surfaces. Solar cells with efficiency larger than 13% can be grown by using AZO etching. Another approach is by using suitable Ga content in absorber layer. Solar cells with efficiency as high as 14.17% are grown which makes thinner CIGS solar cells very competitive.

Download or read book Nanoscale investigation of potential distribution in operating Cu In Ga Se2 thin film solar cells written by Zhenhao Zhang and published by KIT Scientific Publishing. This book was released on 2014-10-16 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The distribution of the electrostatic potential in and between the materials in Cu(In,Ga)Se2 thin-film solar cells has a major impact on their superior performance. This thesis reported on the nanoscale imaging of the electrostatic potential on untreated cross sections of operating Cu(In,Ga)Se2 solar cells using Kelvin probe force microscopy.

Download or read book Studies on Cu2znsnse4 Thin Film As Solar Cell Absorber Layer written by Suresh Babu Gandham and published by LAP Lambert Academic Publishing. This book was released on 2011-08 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar cells have high potential as an alternative energy technology for fulfilling the energy needs. It has the additional advantage being environmentally friendly. Solar photovoltaic cells based on single crystalline Si are prohibitively expensive. Hence, researchers are looking for solar cell materials which are cheap and abundant. Successful thin film solar cells based on CuInGaSe2 uses costly and non-abundant elements like In & Ga, CdTe uses toxic material Cd. To overcome these associated difficulties, we have chosen Cu2ZnSnSe4 thin films which contain elements which are relatively cheap, abundant and less toxic. In this book a brief review of the solar cell absorber layers were presented along with their successes and present market values. Focus is mainly concentrated on the qualities and suitability of Cu2ZnSnSe4 thin films as absorber layers. Preparation (using co-evaporation)and characterization details of this materials are highlighted. Parameters like optimum deposition conditions and ratio between elements re given. Brief description of window preparation and characterization is also presented along with the scope for future work to encourage the readers.

Download or read book Optimization of Process Parameters for Faster Deposition of CuIn1x Gax S2 and CuIn1x Gax Se2 y Sy Thin Film Solar Cells written by Ashwani Kaul and published by . This book was released on 2012 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film solar cells have the potential to be an important contributor to the world energy demand in the 21st century. Among all the thin film technologies, CuInGaSe2 (CIGS) thin film solar cells have achieved the highest efficiency. However, the high price of photovoltaic (PV) modules has been a major factor impeding their growth for terrestrial applications. Reduction in cost of PV modules can be realized by several ways including choosing scalable processes amenable to large area deposition, reduction in the materials consumption of active layers, and attaining faster deposition rates suitable for in-line processing. Selenization-sulfurization of sputtered metallic Cu-In-Ga precursors is known to be more amenable to large area deposition. Sputter-deposited molybdenum thin film is commonly employed as a back contact layer for CIGS solar cells. However, there are several difficulties in fabricating an optimum back contact layer. It is known that molybdenum thin films deposited at higher sputtering power and lower gas pressure exhibit better electrical conductivity. However, such films exhibit poor adhesion to the soda-lime glass substrate. On the other hand, films deposited at lower discharge power and higher pressure although exhibit excellent adhesion show lower electrical conductivity. Therefore, a multilayer structure is normally used so as to get best from the two deposition regimes. A multi-pass processing is not desirable in high volume production because it prolongs total production time and correspondingly increases the manufacturing cost. In order to make manufacturing compliant with an in-line deposition, it is justifiable having fewer deposition sequences. Thorough analysis of pressure and power relationship of film properties deposited at various parameters has been carried out. It has been shown that it is possible to achieve a molybdenum back contact of desired properties in a single deposition pass by choosing the optimum deposition parameters. It is also shown that the film deposited in a single pass is actually a composite structure. CIGS solar cells have successfully been completed on the developed single layer back contact with National Renewable Energy Laboratory (NREL) certified device efficiencies [greater than]11%. The optimization of parameters has been carried out in such a way that the deposition of back contact and metallic precursors can be carried out in identical pressure conditions which is essential for in-line deposition without a need for load-lock. It is know that the presence of sodium plays a very critical role during the growth of CIGS absorber layer and is beneficial for the optimum device performance. The effect of sodium location during the growth of the absorber layer has been studied so as to optimize its quantity and location in order to get devices with improved performance. NREL certified devices with efficiencies [greater than]12% have been successfully completed.

Download or read book Structural and Chemical Analyses of Buffer Layers in Cu In Ga Se2 Thin film Solar Cells written by Daniel Abou-Ras and published by . This book was released on 2005 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: