Download or read book Electronic Grain Boundary Properties in Polycrystalline Cu In Ga Se 1tn2 Semiconductors for Thin Film Solar Cells written by Robert Baier and published by . This book was released on 2012 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Study of Grain Boundaries in Polycrystalline Thin film Solar Cells written by Bingrui Joel Li and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon is one of the most studied semiconductor materials with techniques to control and manipulate its properties well established by the integrated circuit (IC) industry. While silicon wafer-based technology constitutes about 85% of the photovoltaics (PV) market, there are compelling reasons to develop thin-film solar cells. These include potential material cost and energy savings achievable with thin absorber layers of direct band-gap thin film materials, and the potential for incorporation of thin film PV onto inexpensive, flexible, or building material substrates, which opens up the possibility of new applications. Given the success of silicon wafer-based solar cells in the PV market, crystalline silicon on glass is a natural choice for thin-film PV technology. However, the efficiency of this technology is still too low to compete in the PV market. In fact, its record efficiency is only 10.5% which was achieved by CSG Solar. In order to boost the efficiency of this technology, we explore the use of ion-beam assisted deposition (IBAD) to create biaxially-textured silicon films which can potentially have less defects at the grain boundaries. Experimentally, we have fabricated an operational biaxially-textured silicon solar cell whose Voc is likely to have been affected by intra-grain defects as shown by our transmission electron microscopy (TEM) image. In order to investigate the interplay between grain boundary and intra-grain defects on solar cell performance and determine the potential benefits of developing biaxially-textured film solar cells, I used Synopsys' two-dimensional technology computer-aided design (TCAD) Sentaurus simulation tool. In general, the simulations found that biaxially-textured silicon solar cells improve solar cell efficiencies but there is small improvement for devices that have both large grains and low intra-grain carrier lifetime. Among the various thin-film technologies, CdTe and Cu(In, Ga)(S, Se)2 (CIGSSe), dominate the thin-film PV market. However in recent years, the photovoltaic community has seen growing interest in CZTS-based thin-film solar cells which include Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe) and Cu2ZnSn(S, Se)4 (CZTSSe) solar cells. This is driven by their potential to replace Cu(In, Ga)Se2 (CIGSe) and CdTe solar cells which face material scarcity, toxicity and market acceptance issues. In polycrystalline CIGSe-based (CIGSe, CISe, CuGaSe2 (CGSe)) and CdTe solar cells, grain boundaries do not seem to affect solar cell efficiency as much. In fact, some studies have identified grain boundaries as the source of high efficiency in polycrystalline CIGSe-based and CdTe solar cells. CIGSe-based and CZTS-based films are similar in terms of growth methods, optoelectronic and crystallographic properties. Because of these similarities and the benign nature of grain boundaries in CIGSe-based and CdTe films, it would be useful to examine the properties of grain boundaries in these materials. Using scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (C-AFM) techniques, I investigated the electronic properties of grain boundaries in CIGSe, CZTS and CZTSSe solar cells. SKPM measurements carried out in this work reveal a higher positive surface potential at the grain boundaries as compared to the grain while C-AFM measurements show higher current flow in the vicinity of the grain boundaries. These two measurement results are similar to those obtained for high quality CIGSe and CdTe and together they demonstrate the enhanced minority carrier collection taking place at the grain boundaries of CZTS and CZTSSe. Although SKPM measurement are susceptible to topographical and geometric effects, we believe that this effect is not dominating in our measurements as topography and surface potential profile lines are not exact mirror images of one another and regions of similar height have different potentials and vice versa. Nonetheless, I used a technique that involves photoreduction of AgNO3 to provide convincing evidence that our SKPM result is not a result of experimental artifacts but is truly indicative of the higher positive potential at the grain boundary. Having benign or beneficial grain boundaries have been found to be essential for achieving high efficiencies in polycrystalline CIGSe and CdTe solar cells. In my investigation, I found that high efficiency CZTS and CZTSSe solar cells have similar grain boundary electronic properties as high efficiency CIGSe and CdTe solar cells. As such, it might be possible for CZTS and CZTSSe solar cells to achieve similar high efficiencies as CIGSe and CdTe solar cells if other defects (intra-grain, surface and interfacial) are not limiting efficiencies.

Download or read book II IV Compound Semiconductor Photovoltaic Materials Volume 668 written by Robert Birkmire and published by . This book was released on 2001-10-15 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on materials issues related to Cu(In,Ga)(Se,S)2 and CdTe-based polycrystalline thin-film photovoltaic solar cells and related oxides and chalcogenides. Phase equilibrium and thermochemical kinetic aspects of the absorber layer formation of CdTe and Cu(In,Ga)(Se,S)2 are emphasized and several papers on micro-analytical analysis report on detailed structural properties of thin films. The use of flexible plastic or metal foil substrates as an alternative to glass is addressed in terms of solar-cell performance and limitations imposed by the nature of the substrates. Properties of defects and interfaces in CdTe and CIGSS are highlighted using electrical, optical, and micro-analytical tools. While film properties are correlated to device physics, controversy still exists on the detailed operation of both CdTe and CIGSS devices. Topics include: materials and synthesis; thin films on alternate substrates; defects; growth and junction formation; surfaces and interfaces and film and device characterization.

Download or read book Microscopic Properties of Grain Boundaries in Cu In Ga Se2 and CuInS2 Thin film Solar Cells Studied by Transmission Electron Microscopy written by Sebastian Simon Schmidt and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Relation de Zwischen Den Chur Bayrischen dann den Kays vnnd Fr nckischen Cray Trouppen zu Emhoffen an der Vil vnweit Schmidtm hl in dem Pfaltz Neuburgischen vorgangnen Rencontre written by and published by . This book was released on 1703 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Growth and Characterisation of Cu In Ga Se2 Thin Films for Solar Cell Applications written by E. Ahmed and published by . This book was released on 1995 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thin film Polycrystalline Copper indium gallium selenium for Photovoltaic Applications written by Miguel Alberto Contreras and published by . This book was released on 1996 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thin film Polycrystalline Cu In Ga Se for Photovoltaic Applications written by Miguel Alberto Contreras and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Determination of Grain Boundary Charging in Cu In Ga Se2 Thin Films written by and published by . This book was released on 2012 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface potential mapping of Cu(In, Ga)Se2 (CIGS) thin films using scanning Kelvin probe force microscopy (SKPFM) aims to understand the minority-carrier recombination at the grain boundaries (GBs) of this polycrystalline material by examining GB charging, which has resulted in a number of publications. However, the reported results are highly inconsistent. In this paper, we report on the potential mapping by measuring wide-bandgap or high-Ga-content films and by using a complementary atomic force microscopy-based electrical technique of scanning capacitance microscopy (SCM). The results demonstrate consistent, positively charged GBs on our high-quality films with minimal surface defects/charges.

Download or read book Understanding of Defect Physics in Polycrystalline Photovoltaic Materials written by Yanfa Yan and published by . This book was released on 2011 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of thin-film solar cells is influenced by the quality of interfaces and formation of defects such as point defects, stacking faults, twins, dislocations, and grain boundaries. It is important to understand the defect physics so that appropriate methods may be developed to suppress the formation of harmful defects. Here, we review our understanding of defect physics in thin-film photovoltaic (PV) materials such as Si, CdTe, Cu(In, Ga)Se2 (CIGS), Cu2ZnSnSe2 (CZTSe), and Cu2ZnSnS2 (CZTS) using the combination of nanoscale electron microscopy characterization and density-functional theory (DFT). Although these thin-film PV materials share the same basic structural feature - diamond structure based - the defect physics in them could be very different. Some defects, such as stacking faults and special twins, have similar electronic properties in these thin-film materials. However, some other defects, such as grain boundaries and interfaces, have very different electronic properties in these materials. For example, grain boundaries produce harmful deep levels in Si and CdTe, but they do not produce significant deep levels in CIGS, CZTSe, and CZTS. These explain why passivation is critical for Si and CdTe solar cells, but is less important in CIS and CZTS solar cells. We further provide understanding of the effects of interfaces on the performance of solar cells made of these PV materials.

Download or read book Optical Physics of Cu In Ga Se2 Solar Cells and Their Layer Components written by Abedl-Rahman Ibdah and published by . This book was released on 2016 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polycrystalline Cu(In1-xGax)Se2 (CIGS) thin film technology has emerged as a promising candidate for low cost and high performance solar modules. The efficiency of CIGS solar cells is strongly influenced by several key factors. Among these factors include Ga composition and its profile in the absorber layer, copper content in this layer, and the solar cell multilayer structure. As a result, tools for the characterization of thin film CIGS solar cells and their layer components are becoming increasingly essential in research and manufacturing. Spectroscopic ellipsometry is a non-invasive technique that can serve as an accurate probe of component layer optical properties and multilayer structures, and can be applied as a diagnostic tool for real-time, in-line, and off-line monitoring and analysis in small area solar cell fabrication as well as in large area photovoltaics manufacturing. Implementation of spectroscopic ellipsometry provides unique insights into the properties of complete solar cell multilayer structures and their layer components. These insights can improve our understanding of solar cell structures, overcome challenges associated with solar cell fabrication, and assist in process monitoring and control on a production line. In this dissertation research, Cu(In,Ga)Se2 films with different Cu contents have been prepared by the one stage co-evaporation process. These films have been studied by real time spectroscopic ellipsometry (RTSE) during deposition, and by in-situ SE at the deposition temperature as well as at room temperature to extract the dielectric functions (e1, e2) of the thin film materials. Analytical expressions for the room temperature dielectric functions were developed, and the free parameters that describe these analytical functions were in turn expressed as functions of the Cu content. As a result of this parameterization, the dielectric function spectra (e1, e2) can be predicted for any desired composition within the range of the samples investigated. This capability was applied for mapping the structural and compositional variations of CIGS thin films deposited over a 10 cm × 10 cm substrate area. In another application presented in this dissertation, a non-invasive method utilizing ex-situ spectroscopic ellipsometry analysis has been developed and applied to determine non-destructively the Ga compositional profile in CIGS absorbers. The method employs parameterized dielectric function spectra (e1, e2) of CIGS versus Ga content to probe the compositional variation with depth into the absorber. In addition, a methodology for prediction of the external quantum efficiency (QE) including optical gains and losses for a CIGS solar cell has been developed. The methodology utilizes ex-situ spectroscopic ellipsometry analysis of a complete solar cell, with no free parameters, to deduce the multilayer solar cell structure non-invasively and simulate optical light absorption in each of the layer components. In the case of high efficiency CIGS solar cells, with minimal electronic losses, QE spectra are predicted from the sum of optical absorption in the active layer components. For such solar cells with ideal photo-generated charge carrier collection, the SE-predicted QE spectra are excellent representation of the measured ones. Since the QE spectra as well as the short circuit current density (Jsc) can be calculated directly from SE analysis results, then the predicted QE from SE can be compared with the experimental QE to evaluate electronic losses based on the difference between the spectra. Moreover, the calculated Jsc can be used as a key parameter for the design and optimization of anti-reflection coating structures. Because the long term production potential of CIGS solar modules may be limited by the availability of indium, it becomes important to reduce the thickness of the CIGS absorber layer. Thickness reduction would reduce the quantity of indium required for production which would in turn reduce costs. A decrease in short-circuit current density (Jsc) is expected, however, upon thinning the CIGS absorber due to incomplete absorption. To clarify the limits of obtainable Jsc in ultra-thin CIGS solar cells with Mo back contacts, optical properties and multilayer structural data are deduced via spectroscopic ellipsometry analysis and used to predict the QE spectra and maximum obtainable Jsc values upon thinning the absorber. Moreover, SE-guided optical design of ultra-thin CIGS solar cells has been demonstrated. In the case of solar cells fabricated on Mo, thinning the absorber in a CIGS solar cell is associated with significant optical losses in the Mo containing back contact layers. This is due in part to the poor optical reflectance of Mo. Such optical losses may be reduced by employing a back contact design with improved reflectance. Thus, alternative novel solar cell structures with ultra-thin absorbers and improved back contact reflectance have been designed and investigated using SE and the optical modeling methods. In addition to optical losses, electronic losses in the ultra-thin solar cells have been evaluated. By separating the absorber layer into sub-layer regions (for example, near-junction, bulk, and near-back-contact) and varying carrier collection probability in these regions, the contribution of each region to the current can be estimated. Based on this separation, the origin of the electronic losses has been identified as near the back contact.

Download or read book Grain boundary Physics in Polycrystalline Photovoltaic Materials written by and published by . This book was released on 2008 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We use the combination of high-resolution electron microscopy and density-functional theory to study the atomic structure and electronic effects of grain boundaries in polycrystalline photovoltaic materials such as Si, CdTe, CuInSe2, and CuGaSe2. We find that grain boundaries containing dislocation cores create deep levels in Si, CdTe, and CuGaSe2. Surprisingly, however, they do not create deep levels in CuInSe2. We further find that the presence of Ga in grain boundaries in CuInSe2 generates deep levels. These results may explain the fact that Si and CdTe solar cells usually require special passivation, whereas CuInSe2 solar cells do not. The passivation of grain boundaries in Si and CdTe is also studied. We find that grain boundaries in CdTe can be passivated very well by Cl, Br, and I.

Download or read book Local Built in Potential on Grain Boundary of Cu In Ga Se2 Thin Films written by R. Noufi and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on a direct measurement of two-dimensional potential distribution on the surface of Cu(In, Ga)Se2 (CIGS) thin films using a nanoscale electrical characterization of scanning Kelvin probe microscopy (SKPM). The potential measurement reveals a higher surface potential or a smaller work function on grain boundaries (GBs) of the film than on the grain surfaces. This demonstrates the existence of a local built-in potential on GBs and that the GB is positively charged. The role of the built-in potential in device performance was further examined by tuning Ga content or band gap of the film. With increasing Ga content, the GB potential drops sharply in a Ga range of 28%-38%. Comparing the change in the built-in potential to the theoretical and experimental photoconversion efficiencies, we conclude that the potential plays a significant role in the device conversion efficiency of NREL's three-stage CIGS device.

Download or read book Electrical Properties of Grain Boundaries in Low Doped Polycrystalline Materials with Applications to Detectors written by Mazharul Huq Chowdhury and published by . This book was released on 2010 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polycrystalline materials are widely used in large area electronic devices such as flat panel x-ray image detectors, and solar cells due to their suitability to deposit over large area at low cost. The performance of polycrystalline-based flat panel detectors are showing encouraging results (good sensitivity, good resolution and acceptable dark current) and give possibility to replace existing x-ray film/screen cassette. Therefore large area polycrystalline based flat panel detectors have opened new clinical possibilities and the polycrystalline solar cells give the opportunity of manufacturing low cost photovoltaic cells. Consequently, active research has been carried out to find out suitable polycrystalline materials (e.g. HgI2, CdTe, CdZnTe, PbI2, PbO etc) for various large area applications. However a polycrystalline material is composed of micro crystallites joined together by grain boundaries (complex structure, consisting of a few atomic layers of disordered atoms) which posses trap centers for charge carriers. Therefore, grain boundaries can trap a large amount of charges during detector operation. A potential barrier for drifting carriers may exist at the grain boundary, which controls the carrier mobility. Moreover, the performance of these polycrystalline detectors are affected due to the polarization phenomena (any change in the performance of the detector after the detector biasing) under applied bias. Therefore, in this research work, an analytical model is developed to study the electrical properties (electric field and potential distributions, potential barrier height, and polarization phenomenon) of polycrystalline materials at different doping levels for detector and solar cell applications by considering an arbitrary amount of grain boundary charge and a finite width of grain boundary region. The general grain boundary model is also applicable to highly doped polycrystalline materials. The electric field and potential distributions are obtained by solving the Poisson's equation in both depleted grains and grain boundary regions. The electric field and potential distributions across the detector are analyzed under various doping, trapping and applied biases. The electric field collapses, i.e., a nearly zero average electric field region exists in some part of the biased detector at high trapped charge densities at the grain boundaries. The model explains the conditions of existence of a zero average field region, i.e., it explains the polarization mechanisms in polycrystalline materials. The potential barrier at the grain boundary exists if the electric field changes its sign at the opposite side of the grain boundary. The potential barrier does not exist in all grain boundaries in the low doped polycrystalline detector and it never exists in intrinsic polycrystalline detectors under applied bias condition provided there is no charge trapping in the grain.

Download or read book Theory of Graded Bandgap Thin Film Solar Cells written by Faiz Ahmad and published by Morgan & Claypool Publishers. This book was released on 2021-08-24 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin-film solar cells are cheap and easy to manufacture but require improvements as their efficiencies are low compared to that of the commercially dominant crystalline-silicon solar cells. An optoelectronic model is formulated and implemented along with the differential evolution algorithm to assess the efficacy of grading the bandgap of the CIGS, CZTSSe, and AlGaAs photon-absorbing layer for optimizing the power-conversion efficiency of thin-film CIGS, CZTSSe, and AlGaAs solar cells, respectively, in the two-terminal single-junction format. Each thin-film solar cell is modeled as a photonic device as well as an electronic device. Solar cells with two (or more) photon-absorbing layers can also be handled using the optolelectronic model, whose results will stimulate experimental techniques for bandgap grading to enable ubiquitous small-scale harnessing of solar energy.

Download or read book Formation and Electronic Properties of In2S3 Cu in Ga Se2 Junctions and Related Thin Film Solar Cells written by Paul Pistor and published by . This book was released on 2009 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: