Steven Hegedus

Bio: Steven Hegedus is an academic researcher. The author has contributed to research in topics: Solar cell research & Photovoltaic thermal hybrid solar collector. The author has an hindex of 1, co-authored 1 publications receiving 2747 citations.

Handbook of photovoltaic science and engineering

Abstract: About the Editors. List of Contributors. Preface to the 2nd Edition. 1 Achievements and Challenges of Solar Electricity from Photovoltaics (Steven Hegedus and Antonio Luque). 1.1 The Big Picture. 1.2 What is Photovoltaics? 1.3 Photovoltaics Today. 1.4 The Great Challenge. 1.5 Trends in Technology. 1.6 Conclusions. 2 The Role of Policy in PV Industry Growth: Past, Present and Future (John Byrne and Lado Kurdgelashvili). 2.1 Introduction. 2.2 Policy Review of Selected Countries. 2.3 Policy Impact on PV Market Development. 2.4 Future PV Market Growth Scenarios. 2.5 Toward a Sustainable Future. 3 The Physics of the Solar Cell (Jeffery L. Gray). 3.1 Introduction. 3.2 Fundamental Properties of Semiconductors. 3.3 Solar Cell Fundamentals. 3.4 Additional Topics. 3.5 Summary. 4 Theoretical Limits of Photovoltaic Conversion and New-generation Solar Cells (Antonio Luque and Antonio Marti). 4.1 Introduction. 4.2 Thermodynamic Background. 4.3 Photovoltaic Converters. 4.4 The Technical Efficiency Limit for Solar Converters. 4.5 Very-high-efficiency Concepts. 4.6 Conclusions. 5 Solar Grade Silicon Feedstock (Bruno Ceccaroli and Otto Lohne). 5.1 Introduction. 5.2 Silicon. 5.3 Production of Silicon Metal/Metallurgical Grade Silicon. 5.4 Production of Polysilicon/Silicon of Electronic and Photovoltaic Grade. 5.5 Current Silicon Feedstock to Solar Cells. 5.6 Requirements of Silicon for Crystalline Solar Cells. 5.7 Routes to Solar Grade Silicon. 5.8 Conclusions. 6 Bulk Crystal Growth and Wafering for PV (Hugo Rodriguez, Ismael Guerrero, Wolfgang Koch, Arthur L. Endros, Dieter Franke, Christian Hassler, Juris P. Kalejs and H. J. Moller). 6.1 Introduction. 6.2 Bulk Monocrystalline Material. 6.3 Bulk Multicrystalline Silicon. 6.4 Wafering. 6.5 Silicon Ribbon and Foil Production. 6.6 Numerical Simulations of Crystal Growth Techniques. 6.7 Conclusions. 7 Crystalline Silicon Solar Cells and Modules (Ignacio Tobias, Carlos del Ca"nizo and Jesus Alonso). 7.1 Introduction. 7.2 Crystalline Silicon as a Photovoltaic Material. 7.3 Crystalline Silicon Solar Cells. 7.4 Manufacturing Process. 7.5 Variations to the Basic Process. 7.6 Other Industrial Approaches. 7.7 Crystalline Silicon Photovoltaic Modules. 7.8 Electrical and Optical Performance of Modules. 7.9 Field Performance of Modules. 7.10 Conclusions. 8 High-efficiency III-V Multijunction Solar Cells (D. J. Friedman, J. M. Olson and Sarah Kurtz). 8.1 Introduction. 8.2 Applications. 8.3 Physics of III-V Multijunction and Single-junction Solar Cells. 8.4 Cell Configuration. 8.5 Computation of Series-connected Device Performance. 8.6 Materials Issues Related to GaInP/GaAs/Ge Solar Cells. 8.7 Epilayer Characterization and Other Diagnostic Techniques. 8.8 Reliability and Degradation. 8.9 Future-generation Solar Cells. 8.10 Summary. 9 Space Solar Cells and Arrays (Sheila Bailey and Ryne Raffaelle). 9.1 The History of Space Solar Cells. 9.2 The Challenge for Space Solar Cells. 9.3 Silicon Solar Cells. 9.4 III-V Solar Cells. 9.5 Space Solar Arrays. 9.6 Future Cell and Array Possibilities. 9.7 Power System Figures of Merit. 9.8 Summary. 10 Photovoltaic Concentrators (Gabriel Sala and Ignacio Anton). 10.1 What is the Aim of Photovoltaic Concentration and What Does it Do? 10.2 Objectives, Limitations and Opportunities. 10.3 Typical Concentrators: an Attempt at Classification. 10.4 Concentration Optics: Thermodynamic Limits. 10.5 Factors of Merit for Concentrators in Relation to the Optics. 10.6 Photovoltaic Concentration Modules and Assemblies. 10.7 Tracking for Concentrator Systems. 10.8 Measurements of Cells, Modules and Photovoltaic Systems in Concentration. 10.9 Summary. 11 Crystalline Silicon Thin-Film Solar Cells via High-temperature and Intermediate-temperature Approaches (Armin G. Aberle and Per I. Widenborg). 11.1 Introduction. 11.2 Modelling. 11.4 Crystalline Silicon Thin-Film Solar Cells on Intermediate-T Foreign Supporting Materials. 11.5 Conclusions. 12 Amorphous Silicon-based Solar Cells (Eric A. Schiff, Steven Hegedus and Xunming Deng). 12.1 Overview. 12.2 Atomic and Electronic Structure of Hydrogenated Amorphous Silicon. 12.3 Depositing Amorphous Silicon. 12.4 Understanding a-Si pin Cells. 12.5 Multijunction Solar Cells. 12.6 Module Manufacturing. 12.7 Conclusions and Future Projections. 13 Cu(InGa)Se2 Solar Cells (William N. Shafarman, Susanne Siebentritt and Lars Stolt). 13.1 Introduction. 13.2 Material Properties. 13.3 Deposition Methods. 13.4 Junction and Device Formation. 13.5 Device Operation. 13.6 Manufacturing Issues. 13.7 The Cu(InGa)Se2 Outlook. 14 Cadmium Telluride Solar Cells (Brian E. McCandless and James R. Sites). 14.1 Introduction. 14.2 Historical Development. 14.3 CdTe Properties. 14.4 CdTe Film Deposition. 14.5 CdTe Thin Film Solar Cells. 14.6 CdTe Modules. 14.7 Future of CdTe-based Solar Cells. 15 Dye-sensitized Solar Cells (Kohjiro Hara and Shogo Mori). 15.1 Introduction. 15.2 Operating Mechanism of DSSC. 15.3 Materials. 15.4 Performance of Highly Efficient DSSCs. 15.5 Electron-transfer Processes. 15.6 New Materials. 15.7 Stability. 15.8 Approach to Commercialization. 15.9 Summary and Prospects. 16 Sunlight Energy Conversion Via Organics (Sam-Shajing Sun and Hugh O'Neill). 16.1 Principles of Organic and Polymeric Photovoltaics. 16.2 Evolution and Types of Organic and Polymeric Solar Cells. 16.3 Organic and Polymeric Solar Cell Fabrication and Characterization. 16.4 Natural Photosynthetic Sunlight Energy Conversion Systems. 16.5 Artificial Photosynthetic Systems. 16.6 Artificial Reaction Centers. 16.7 Towards Device Architectures. 16.8 Summary and Future Perspectives. 17 Transparent Conducting Oxides for Photovoltaics (Alan E. Delahoy and Sheyu Guo). 17.1 Introduction. 17.2 Survey of Materials. 17.3 Deposition Methods. 17.4 TCO Theory and Modeling: Electrical and Optical Properties and their Impact on Module Performance. 17.5 Principal Materials and Issues for Thin Film and Wafer-based PV. 17.6 Textured Films. 17.7 Measurements and Characterization Methods. 17.8 TCO Stability. 17.9 Recent Developments and Prospects. 18 Measurement and Characterization of Solar Cells and Modules (Keith Emery). 18.1 Introduction. 18.2 Rating PV Performance. 18.3 Current-Voltage Measurements. 18.4 Spectral Responsivity Measurements. 18.5 Module Qualification and Certification. 18.6 Summary. 19 PV Systems (Charles M. Whitaker, Timothy U. Townsend, Anat Razon, Raymond M. Hudson and Xavier Vallve). 19.1 Introduction: There is gold at the end of the rainbow. 19.2 System Types. 19.3 Exemplary PV Systems. 19.4 Ratings. 19.5 Key System Components. 19.6 System Design Considerations. 19.7 System Design. 19.8 Installation. 19.9 Operation and Maintenance/Monitoring. 19.10 Removal, Recycling and Remediation. 19.11 Examples. 20 Electrochemical Storage for Photovoltaics (Dirk Uwe Sauer). 20.1 Introduction. 20.2 General Concept of Electrochemical Batteries. 20.3 Typical Operation Conditions of Batteries in PV Applications. 20.4 Secondary Electrochemical Accumulators with Internal Storage. 20.5 Secondary Electrochemical Battery Systems with External Storage. 20.6 Investment and Lifetime Cost Considerations. 20.7 Conclusion. 21 Power Conditioning for Photovoltaic Power Systems (Heribert Schmidt, Bruno Burger and Jurgen Schmid). 21.1 Charge Controllers and Monitoring Systems for Batteries in PV Power Systems. 21.2 Inverters. 22 Energy Collected and Delivered by PV Modules (Eduardo Lorenzo). 22.1 Introduction. 22.2 Movement between Sun and Earth. 22.3 Solar Radiation Components. 22.4 Solar Radiation Data and Uncertainty. 22.5 Radiation on Inclined Surfaces. 22.6 Diurnal Variations of the Ambient Temperature. 22.7 Effects of the Angle of Incidence and of Dirt. 22.8 Some Calculation Tools. 22.9 Irradiation on Most Widely Studied Surfaces. 22.10 PV Generator Behaviour Under Real Operation Conditions. 22.11 Reliability and Sizing of Stand-alone PV Systems. 22.12 The Case of Solar Home Systems. 22.13 Energy Yield of Grid-connected PV Systems. 22.14 Conclusions. 23 PV in Architecture (Tjerk H. Reijenga and Henk F. Kaan). 23.1 Introduction. 23.2 PV in Architecture. 23.3 BIPV Basics. 23.4 Steps in the Design Process with PV. 23.5 Concluding Remarks. 24 Photovoltaics and Development (Jorge M. Huacuz, Jaime Agredano and Lalith Gunaratne). 24.1 Electricity and Development. 24.2 Breaking the Chains of Underdevelopment. 24.3 The PV Alternative. 24.4 Examples of PV Rural Electrification. 24.5 Toward a New Paradigm for Rural Electrification. References. Index.

Coaxial silicon nanowires as solar cells and nanoelectronic power sources

Abstract: Solar cells are attractive candidates for clean and renewable power; with miniaturization, they might also serve as integrated power sources for nanoelectronic systems. The use of nanostructures or nanostructured materials represents a general approach to reduce both cost and size and to improve efficiency in photovoltaics. Nanoparticles, nanorods and nanowires have been used to improve charge collection efficiency in polymer-blend and dye-sensitized solar cells, to demonstrate carrier multiplication, and to enable low-temperature processing of photovoltaic devices. Moreover, recent theoretical studies have indicated that coaxial nanowire structures could improve carrier collection and overall efficiency with respect to single-crystal bulk semiconductors of the same materials. However, solar cells based on hybrid nanoarchitectures suffer from relatively low efficiencies and poor stabilities. In addition, previous studies have not yet addressed their use as photovoltaic power elements in nanoelectronics. Here we report the realization of p-type/intrinsic/n-type (p-i-n) coaxial silicon nanowire solar cells. Under one solar equivalent (1-sun) illumination, the p-i-n silicon nanowire elements yield a maximum power output of up to 200 pW per nanowire device and an apparent energy conversion efficiency of up to 3.4 per cent, with stable and improved efficiencies achievable at high-flux illuminations. Furthermore, we show that individual and interconnected silicon nanowire photovoltaic elements can serve as robust power sources to drive functional nanoelectronic sensors and logic gates. These coaxial silicon nanowire photovoltaic elements provide a new nanoscale test bed for studies of photoinduced energy/charge transport and artificial photosynthesis, and might find general usage as elements for powering ultralow-power electronics and diverse nanosystems.

Band-gap energy estimation from diffuse reflectance measurements on sol–gel and commercial TiO2: a comparative study

Abstract: A comparison of the band gap energy estimated from UV–vis reflectance spectra of TiO2 powders prepared by sol–gel route versus commercial TiO2 powders, nanopowder, bulkpowder and P25 is reported. The experimental results obtained from the optical absorption spectra were reported for all the TiO2 samples. Graphic representations were used to calculate Eg: absorbance versus λ; F(R) versus E; (F(R) hν)n versus E, with n = ½ for an indirect allowed transition and n = 2 for a direct allowed transition. From the results, it could be seen that Eg strongly varied according to the equation used for the graphic representation. Differences in Eg up to 0.5 eV for the same semiconductor depending on the transition chosen were observed. Accurate Eg estimation in the four semiconductors studied was obtained by using the general equation α (hν) ≈ B (hν − Eg)n (where α ~ F(R)) and indirect allowed transition.

High-performance flat-panel solar thermoelectric generators with high thermal concentration

Abstract: The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. A highly efficient solar to electric energy conversion device based on nanostructured thermoelectric materials and high solar concentration is now demonstrated. The results show potential for cost effective solar thermoelectric generation.

A Review of Solar Photovoltaic Levelized Cost of Electricity

Abstract: As the solar photovoltaic (PV) matures, the economic feasibility of PV projects are increasingly being evaluated using the levelized cost of electricity (LCOE) generation in order to be compared to other electricity generation technologies. Unfortunately, there is lack of clarity of reporting assumptions, justifications and degree of completeness in LCOE calculations, which produces widely varying and contradictory results. This paper reviews the methodology of properly calculating the LCOE for solar PV, correcting the misconceptions made in the assumptions found throughout the literature. Then a template is provided for better reporting of LCOE results for PV needed to influence policy mandates or make invest decisions. A numerical example is provided with variable ranges to test sensitivity, allowing for conclusions to be drawn on the most important variables. Grid parity is considered when the LCOE of solar PV is comparable with grid electrical prices of conventional technologies and is the industry target for cost-effectiveness. Given the state of the art in the technology and favorable financing terms it is clear that PV has already obtained grid parity in specific locations and as installed costs continue to decline, grid electricity prices continue to escalate, and industry experience increases, PV will become an increasingly economically advantageous source of electricity over expanding geographical regions.