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This article examines some of the basic questions about silicon module recycling: (1) What can be recovered from silicon modules? (2) What recycling technologies are needed? (3) What are the potential revenues for different recycling scenarios? And (4) what are the major challenges for different recycling scenarios? Three recycling scenarios are considered: module reuse, component extraction, and material extraction. Recycling process sequences for different scenarios are outlined. The discussions conclude that module reuse generates the highest revenue with the fewest processing steps, while material extraction leads to the lowest revenue with the most processing steps. It is suggested that gentle and clean separation of silicon solar cells from the glass pane is a critical technology for silicon module recycling. It is also argued that two low-concentration metals must be recovered from silicon modules: silver as a scarce material and lead as a toxic material. Their recovery requires chemical methods, while bulky materials including glass cullet, aluminum frame, and copper wiring can be recovered with physical methods. The silicon in the cells can be extracted with different qualities: ferro-silicon, metallurgical-grade silicon, or solar-grade silicon, with a higher revenue and more complicated recycling process for purer silicon. Markets outside the solar industry for the recovered silicon should be explored. The biggest challenge for module reuse is to find a large and sustained market for hundreds of gigawatts peak of decommissioned modules a year, and the biggest challenge for component extraction is the many different module and cell structures on the market and cell efficiency variability. For all the three scenarios, the cost of collecting and processing waste modules is a common challenge.

Given the increasing interest in tandem silicon-based solar cells and the recent advances in luminescent solar concentrators, the luminescent solar concentrators/silicon tandem structure has been proposed as an option for a four-terminal tandem structure. As part of the evaluation of a new type of solar cell, it is important to conduct a Life Cycle Assessment to effectively guide research efforts towards cell designs with minimum environmental impacts. Here, we carry out a process-based Life Cycle Assessment to assess global warming, human toxicity (carcinogenic and non-carcinogenic), freshwater eutrophication and ecotoxicity and abiotic depletion potential impacts associated with three luminescent solar concentrators/silicon tandem cell structures, considering a bottom layer as being a passivated emitter rear contact silicon solar cell. The results are based on experimental parameters and show that the increase in the performance of the cells and modules using the studied tandem structure can produce lower environmental effects than the passivated emitter rear contact technology (single-junction) for the impact categories studied. These results encourage the studies on cell and module performance improvements using such tandem luminescent solar concentrators/silicon structures.

Energy is an essential need of people; however, people living in displacement settings are often deprived of this basic need. Connecting refugee camps through the main grid is challenging due to their locations. Biogas is an energy source that can be implemented to address the energy need of refugee camps. Implementation of biogas technology can help to reach sustainable development goal-7 (SDG 7) and its synergies in refugee camps. Therefore, in this study, the contribution of biogas in achieving sustainable development goals is presented to address the current gap in the literature. For this, Rohingya refugees in Bangladesh were considered as a case study. The waste situation in Rohingya refugee camps is highlighted and considered. Generated biogas from the organic fraction municipal solid (OFMSW) was used to determine the LPG cylinder reduction potential in Rohingya refugee camps. Approximately 497,587 LPG cylinders can be replaced if biogas is used in cooking activities. Moreover, compared to wood fuel, biogas used in cookstoves emits 85% less greenhouse gas. This study underlines the importance of further research to determine the prospective use of biogas in clean cooking in refugee camps.

This chapter presents a critical review of life cycle assessment (LCA) studies of solar photovoltaic (PV) technologies considering their technological and ecological developments, including silicon (Si)-based cells and modules (mono- and multicrystalline), thin-film cells and modules such as chalcogenides (CIS, CIGS, and CZTS), amorphous-Si (a-Si), cadmium telluride (CdTe), dye-sensitized solar cells (DSSCs), organic photovoltaics (OPV), and organic–inorganic halide perovskite (perovskite); PV systems (grid-connected, stand-alone, mounting methods, balance of system); and end-of-life (EoL) scenarios (such as landfill, incineration, and recycling). The reviews show that several studies are not using PV guideline assumptions, which results in a untrustworthy database. Assumptions of parameter values for LCA studies can have profound effects on results, and current assumptions are unrealistic relative to demonstrated results for several of the reviewed studies. Thus, while thin films appear to have better environmental outcomes (regarding global warming potential and energy payback time), this conclusion is not definitive given the current consistency of data. Quantitatively, the normalized global warming potential for thin-film technologies is 22–40 gCO2eq/kWh, followed by OPV 30–150 gCO2eq/kWh, followed by both crystalline silicon (c-Si) in the range of 40–200 gCO2eq/kWh and perovskite 150–1000 gCO2eq/kWh. However, LCA for c-Si technologies are currently more reliable than other technologies, given the latter's lack of consistency and assumption reliability. This review also identifies important challenges the field currently faces: (i) There is a shortage of data associated with end-of-life management of PV systems. (ii) The balance of system has been found to have significant impact and is often neglected in LCA studies. (iii) Likewise, transportation has significant environmental impacts, but data for this input is currently scarce. The same can be said for data on monitoring and reporting of a system's conditions. (iv) There is also a lack of economic analysis on material recovery from solar modules.

The diesel-electric power supply to the Montague Island nature reserve has been replaced by a photovoltaic/diesel/battery hybrid system, resulting in 87% decrease in fuel use with attendant reduction in environmental risk. Thorough electrical and environmental monitoring is carried out to enable improvements and for educational purposes. System performance and load management are reviewed.

This paper examines three recycling scenarios for silicon panels: panel reuse, component extraction, and material extraction. Recycling process sequences, recycling technologies, and potential revenues for different scenarios are discussed. The main conclusions of the paper include: 1) separation of silicon cells from glass is a critical technology; 2) low-concentration silver and lead must be recovered from silicon panels; 3) markets outside the solar industry for the recovered silicon should be explored; and 4) cell efficiency standardization can improve the recyclability of silicon panels.

The screen-printed aluminium back surface field (Al-BSF) technology is the current industry standard process for crystalline silicon solar cells but, due to the search for higher efficiency, much attention has been paid to the passivated emitter and rear cell (PERC), which is gaining significant share in the world market. We undertake an environmental analysis comparing Al-BSF and PERC monocrystalline solar modules. Through the life cycle assessment (LCA) method we calculate the global warming, human toxicity (cancer and non-cancer effects), freshwater eutrophication, freshwater ecotoxicity, abiotic depletion potentials and energy payback time of these technologies considering solar, electronic and upgraded metallurgical grade silicon feedstock. The functional unit considered is 1 kWh of energy delivered over the modules’ lifetime. As a result of this work, we showed that PERC technology generates a slight improvement in the environmental impacts when compared with Al-BSF. The use of electronic and upgraded metallurgical grade silicon results in lower environmental impacts in most cases, compared with the other technologies analysed, based on the assumptions made in this LCA.

Tandem technologies offer potential price reductions and higher efficiencies of PV modules. The high band gap nature of chalcogenides like CIGS, CZTS and AZTS makes them excellent materials for use on top of a Si base tandem cells. Nevertheless, along with the search for new technologies, there is also the concern about the environmental impact that its lifetime can cause. A comprehensive life cycle assessment for CIGS/Si, CZTS/Si and AZTS/Si tandem solar modules was not reported to date. This work compares the environmental impacts of Si and chalcogenide/Si tandem solar modules, assessing global warming potential, human toxicity potential (cancer and non-cancer effects), freshwater eutrophication potential, freshwater ecotoxicity potential, abiotic depletion potential and the energy payback time of these technologies. The results of this study show that compared with Si, CIGS/Si presents worse environmental impacts for most of the categories but, on the other hand, CZTS/Si and AZTS/Si present better outcomes for most of the impacts categories. We can also say that higher efficiency of these tandem technologies could potentially reverse that result. This LCA provides design advice for the R&D community, showing which structure has the best environmental outcomes and which processes should be optimized to achieve better results.

The rapid global uptake of solar photovoltaics (PV) promises the hope of affordable low-carbon electricity. Most production of PV modules so far, and for the foreseeable future, has been based on silicon wafer cells and while there are further R&D outcomes still to be fully transferred to the silicon cell industry, the next major technology change is likely to be the addition of a thin-film top cell to form an efficient tandem device. The authors have applied life cycle assessment (LCA) to several of the current and potential mass manufactured solar cell technology choices, including different silicon wafer styles and silicon/thin-film tandems. We have demonstrated that the environmental benefits of some paths for efficiency improvements, particularly of the incorporation of atomic hydrogen into silicon wafers, more than compensate for the additional inputs required. Furthermore, we have shown that the stability of top-cell materials for tandems is paramount, to avoid the premature demise of the underlying silicon bottom cell.The end-of-life has been assumed to be landfill in most preceding LCA studies but there is a growing global need for PV recycling due to the rapid rise in uptake of photovoltaics, which will result in a significant future waste stream. Europe is leading the world in requiring industry stewardship for photovoltaics (and batteries, inverters and other system components) and other jurisdictions, including Australia, are following. However, photovoltaic modules are difficult to dismantle or deconstruct for materials recovery by methods that are both financially and environmentally sustainable. We will use LCA to guide our research on module recycling by chemical, thermal and mechanical methods and their combinations, with an aim to maximize the value of the recovered materials.

Building-integrated photovoltaic technology (BIPV) is a decentralised renewable energy source with a building material function. Lack of confidence in the economic viability of BIPV has become one of the critical issues in investment decisions. Therefore, there is a need to review the real economic value of recent BIPV projects to dispel the common myth of the high cost of BIPV. This paper reviews forty-five (45) BIPV projects attached to non-domestic buildings located in twelve (12) western countries between 2009 and 2018 to understand their real economic value. Levelized cost energy, net present value and discounted payback periods are estimated to identify both direct and indirect benefits of BIPV. The economic assessment revealed that projects are economically feasible when both direct and indirect are measured. Analysis further discovered that 1) curtain wall, double-skin facades, discontinuous roofs and skylights among the building application types, 2) educational buildings among the functions of non-domestic buildings and 3) c-Si among the module technologies are economically feasible performances. BIPVs are complex and unique designs with diverse economic performances. It is important to carefully select the parameters to assess the performance levels of the application before any decision is made. The study confirms that understanding the broad values facilitates the quantification of the real contribution of BIPV. The outcome of the paper assists decision-makers and policymakers in developing strategies to decide BIPV adoption.

Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different commercial or semi-commercial LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6h. Five log10 and greater reductions were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6h). No significant disinfection was observed with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were observed, particularly with UV-A wavelengths. The radiation doses required for >3-log10 reduction of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were observed with both indicators. The design process revealed cost and technical constraints pertaining to LED electrical efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technology is already technically possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work.

Photovoltaic (PV) panel manufacturing is increasing worldwide, which subsequently increases the amount of waste PV. This study proposes to recycle waste PV using organic solvent delamination followed by downstream thermal and leaching procedures. Firstly, experimental data is obtained using small commercial modules by replicating a recycling route taken from the literature. Based on the experimental results, life cycle cost analysis (LCCA) and life cycle assessment (LCA) are applied to evaluate the experimental and optimized industry scale processes. Results show that the main profitable recycling avenues are for aluminum frame and junction box removal; and that downstream processes can separate and recover all the remaining materials, but not profitably. The laboratory and high-throughput-optimized processes, considering the median costs and revenues, have a net cost of 29.00 and 3.30 USD per module, respectively. The complete recovery of materials using the proposed method is unlikely to be profitable and this may only be achievable where labor is not expensive. Alternatively, the complete recycling of waste PV could be made economically viable by reducing process time, increasing automation and/or providing financial subsidies. The environmental analysis, however, shows that the optimized process modelled here has a positive net environmental impact. The results are also compared against the cost/environmental impact of landfilling such waste. In summary, the proposed recycling route is capable of completely recovering the main materials in waste PV (aluminum frames, junction box, silver, copper tabbing, silicon, backsheet and unbroken glass) and can have a positive environmental impact, but it is not economically profitable.

Hydrogenation processes can offer improvements to the electrical performance of silicon (Si) solar cells from different feedstocks, including low-cost feedstocks, such as upgraded metallurgical silicon (UMG-Si). The development of PV technologies should be complemented by environmental analyses of the production processes. Here we undertake an environmental analysis of Si solar modules including the addition of hydrogenation processes through the life cycle assessment (LCA) method. LCA has not been applied to Si technologies such as hydrogenation, to the best of authors' knowledge. We show that the hydrogenation methods result in better environmental outcomes, considering the assumptions made in this LCA.

For many decades, populations in rural and remote developing regions will be unable to access centralised piped potable water supplies, and indeed, decentralised options may be more sustainable. Accordingly, improved household point-of-use (POU) disinfection technologies are urgently needed. Compared to alternatives, ultraviolet (UV) light disinfection is very attractive because of its efficacy against all pathogen groups and minimal operational consumables. Though mercury arc lamp technology is very efficient, it requires frequent lamp replacement, involves a toxic heavy metal, and their quartz envelopes and sleeves are expensive, fragile and require regular cleaning. An emerging alternative is semiconductor-based units where UV light emitting diodes (UV-LEDs) are powered by photovoltaics (PV). Our review charts the development of these two technologies, their current status, and challenges to their integration and POU application. It explores the themes of UV-C-LEDs, non-UV-C LED technology (e.g. UV-A, visible light, Advanced Oxidation), PV power supplies, PV/LED integration and POU suitability. While UV-C LED technology should mature in the next 10 years, research is also needed to address other unresolved barriers to in situ application as well as emerging research opportunities especially UV-A, photocatalyst/photosensitiser use and pulsed emission options.

A survey has been carried out of graduates and employers working in the sustainable energy (SE) industry in Australia. The aims were to identify the key areas of content to be included in University level SE training and the type of degree structures that are most appropriate for SE professionals. Attention was also directed to the mode of instruction (online, blended or face-to-face) and the role of work-integrated learning (WIL). This paper presents the results of the survey, which provide guidance to Universities seeking to develop new, or revise existing, SE education offerings. The results of the survey clearly indicate that responding students and employers prefer a generalist degree in engineering, with a stream in sustainable energy as the initial qualification for professionals in this field. Specialist degrees at postgraduate level were also considered appropriate for continuing professional education (CPE). Both graduates and employers agreed on key areas to be included in the SE courses. These key areas are generic skills (research methods, team work, report writing), generation technologies (especially PV, wind and biomass), and enablers (such as economics, policy and project management). The graduates, many of whom came from overseas countries, generally agreed about the course content and its relevance to employment in their countries. Face-to-face or blended learning was preferred by both groups as the mode of instruction for the first degree. Online learning was considered a valuable adjunct in the undergraduate course and more suitable for CPE in postgraduate courses. WIL and more practical work were considered important, especially in the first degree. There was some disagreement about the appropriate length of work placements, with graduates preferring 6–8 weeks and employers 10–12 weeks. This work should provide a basis for further course development and curriculum reform for sustainable energy education.

The effect of electron range on electron beam induced current (EBIC) is demonstrated and the problem of the choice of the optimal electron ranges to use with simple uniform and point generation function models is resolved by proposing a method to extract an electron range–energy relationship (ERER). The results show that the use of these extracted electron ranges remove the previous disagreement between the EBIC curves computed with simple forms of generation model and those based on a more realistic generation model. The impact of these extracted electron ranges on the extraction of diffusion length, surface recombination velocity and EBIC contrast of defects is discussed. It is also demonstrated that, for the case of uniform generation, the computed EBIC current is independent of the assumed shape of the generation volume.

The Australian Centre for Advanced Photovoltaics (ACAP) co-ordinates the activities of the six Australian research institutions and a group of industrial partners in the Australia-US Institute for Advanced Photovoltaics (AUSIAPV) to develop the next generations of photovoltaic device technology and to provide a pipeline of opportunities for performance increase and cost reduction. AUSIAPV links ACAP with US-based partners. These national and international research collaborations provide a pathway for highly visible, structured photovoltaic research collaboration between Australian and US researchers, institutes and agencies with significant joint programs based on the clear synergies between the participating organizations. The research program is organized in five collaborative Program Packages (PPs). PP1 deals with silicon wafer-based cells, focusing on three main areas: cells from solar grade silicon, rear contact and silicon-based tandem cells. PP2 involves research into a range of organic solar cells, organic/inorganic hybrid cells, "earth abundant" thin-film materials and "third generation" approaches. PP3 is concerned with optics and characterization. PP4 will deliver a substantiated methodology for assessing manufacturing costs of the different technologies and PP5 involves education, training and outreach. The main research topics, results and plans for the future are presented.

The concept of third generation photovoltaics is to significantly increase device efficiencies whilst still using thin film processes and abundant non-toxic materials. This can be achieved by circumventing the Shockley–Queisser limit for single band gap devices, using multiple energy threshold approaches. At the University of NSW, as part of our work on Third Generation devices, we are using the energy confinement of silicon based quantum dot nanostructures to engineer wide band gap materials to be used as upper cell elements in Si based tandem cells. HRTEM data shows Si nanocrystal formation in oxide and nitride matrixes with a controlled nanocrystal size, grown by layered reactive sputtering and layered PECVD. Photoluminescence evidence for quantum confinement in the Si quantum dots in oxide agrees with the calculated increase in PL energy with reduction in dot size. Resistivity measurements with temperature give tentative proof of conduction and we are investigating junction formation in these materials. We are also using similar Si quantum dot structures in double barrier resonant tunneling structures for use in hot carrier solar cell contacts. These must collect carriers over a limited energy range. Negative differential resistance has been observed in room temperature I–V on these samples, a necessary proof of concept for selective energy filter contacts.

Photovoltaic (solar) cells (Corkish 2004) are semiconductor devices that directly create electric current and voltage from the collection of photons (quanta of light). They convert sunlight to electricity silently and without moving parts, require little maintenance, are reliable, are being sold with warranties of up to twenty-five years, generate no greenhouse gases in operation, and are modular, rapidly deployable and particularly suited to urban rooftops, facades, and similar applications. Hence, they are easily located close to where electricity is consumed. Solar cells of 15% efficiency covering an area equivalent to just 0.25% of the global area under crops and permanent pasture could meet all the world's primary energy requirements today (Archer and Hill 2001), yet most or all of that area could be otherwise alienated land, such as on buildings, for example. “On any given day, the solar energy falling on a typical oilfield in the Middle East is far greater than the energy contained in the ...

Thermal oxidation of a silicon-on-insulator substrate produces evidence that an ordered SiO2 structure can exist on thermally oxidized SiO2–Si interfaces. An apparently ordered SiO2 layer was observed by a high-resolution transmission electron microscope (HRTEM) when a thin silicon layer enclosed by SiO2 was less than 3.0nm thick. X-ray diffraction of the ultrathin Si (

Thermophotovoltaics involves the photovoltaic conversion by a receiver cell of radiation from an emitter, which could be heated by various sources including sunlight. A prime difference from normal solar photovoltaics is that emitted energy unable to be used by the receiver can, in principle, be recycled allowing high conversion efficiency. Thermophotonics is a recent development of this concept where the emitter is “active”, namely a heated diode, increasing the rate of energy transfer for a given emitter temperature and concentrating emission in an energy range more suited for conversion by the receiver. This paper evaluates thin semiconducting layers as emitters for thermophotovoltaics and thermophotonics. It is shown that thermophotonics avoids a major challenge for thermophotovoltaics: the sensitive dependence of system efficiency on the recycling of below bandgap radiation. Possible ways of achieving the high external quantum efficiency light-emitting diode required for thermophotonics are discussed.

The idea of collecting solar electromagnetic radiation with antenna-rectifier (rectenna) structures was proposed three decades ago but has not yet been achieved. The idea has been promoted as having potential to achieve efficiency approaching 100% but thermodynamic considerations imply a lower limit of 85.4% for a non-frequency-selective rectenna and 86.8% for one with infinite selectivity, assuming maximal concentration in each case. This paper reviews the history and technical context of solar rectennas and discusses the major issues: thermodynamic efficiency limits, rectifier operation at optical frequencies, harmonics production and electrical noise.

Solar cell efficiency limit are receiving renewed examination due to the realisation that many types of solar cell structures can theoretically achieve similar efficiencies to those of multiple p–n homojunctions, without the need for a large number of different semiconductors. This paper shows that the proposed high efficiency device structures fit into one of three general classes and therefore only three ideal efficiency limit calculations are required. However, many of the suggested structures violate assumptions in the ideal efficiency limit calculations. Hence, these calculations should be modified to include additional transport, generation and recombination effects.

Multi-band solar cells provide a possible approach to obtain photovoltaic efficiencies that are greater than that of a single junction solar cell. In the three-band case, an intermediate band harnesses photons of energy less than that between the two main bands, allowing these photons to contribute to the power output of the device. Previous work has shown that introducing a third band offers an efficiency of 63.2%. This paper extends the theory to four bands and calculates a limiting efficiency of 71.7%. Finite bandwidths of all bands can be used to ensure photon absorption selectivity, assumed in deducing the previous limits, but at the cost of reduced limiting efficiency. The maximum efficiency using this feature for the three and four bands is 58.9% and 59.0%, respectively. Superlattices and quantum dots offer flexibility in artificially designing the energy and widths of the bands.

Thermophotovoltaics involves the photovoltaic conversion by a receiver cell of radiation from an emitter which could be heated by various sources including sunlight. A prime difference from normal solar photovoltaics is that emitted energy unable to be used by the receiver, in principle, can be recycled allowing high conversion efficiency. Thermophotonics is a recent development of this concept where the emitter is “active”, namely a heated diode, increasing the rate of energy transfer for a given emitter temperature and concentrating emission in an energy range more suited for conversion by the receiver. Even as “passive selective emitters”, thin semiconducting layers may provide an alternative offering increased design flexibility to standard rare-earth doped ceramics. The decreased emitter band gap at high temperature means that for spectral matching, the room temperature band gap of the emitter should be slightly higher than that of the absorber. Low-dimensional structures such as quantum wells, superlattices and nanocrystals offer scope for such band-gap control and for enhanced luminescence.

Following recent progress in the study of limiting efficiencies of photovoltaic devices with multiple energy levels, we suggest using the impurity photovoltaic (IPV) effect in wide-bandgap semiconductors as a means to achieve very-high-efficiency solar cells. We discuss the requirements for a high-efficiency IPV device and review some of the material systems that could be used. As a case study, we investigate theoretically β-SiC IPV solar cells with a model based on a modified Shockley–Read–Hall theory. The high-efficiency potential is confirmed and the important issues for implementation are presented and discussed. Copyright © 2002 John Wiley &; Sons, Ltd.

Three-dimensional numerical simulations of electron-beam-induced current (EBIC) near a vertical silicon grain boundary are demonstrated. They are compared with an analytical model which excludes the effect of carrier generation other than in the bulk base region of a solar cell structure. We demonstrate that in a wide range of solar cell structures recombination in the space charge region (SCR) significantly affects the EBIC results and hence needs to be included in the data evaluation. Apart from these findings, simulations of a realistic silicon solar cell structure (thick emitter, field-dependent mobility, etc.) are demonstrated.

A central assumption in detailed balance efficiency limit calculations has been that the light generated carriers are collected by drift transport processes and have an infinite mobility, giving rise to constant quasi-Fermi levels (RFLs) across the solar cell. However, recent experimental and theoretical results for quantum well (QW) devices indicate that the QFLs need not be constant across the device. It is shown in this paper that transport mechanisms which cause a variation in the difference between the electron and hole QFLs give an increase in the limiting efficiency compared to previous detailed balance calculations. Further, QW solar cells which employ hot carrier transport across a well will have an efficiency limit in excess of a tandem solar cell while using the same number of semiconductor materials.

An improved method is described for extracting material parameters from an experimental electron-beam-induced current (EBIC) contrast profile across a vertical grain boundary by directly fitting an analytical expression. This allows the least-squares values of the grain boundary recombination velocity and the diffusion length in each grain to be determined without the need for the reduction of the experimental profile to a few integral parameters, as is required in a previously reported method. Greater accuracy of the extracted values is expected since none of the information contained in the experimental contrast data is discarded and a less extensive spatial range of measured data is required than in the commonly used method. Different models of the carrier generation volume are used in the fitting and the effect of the choice of generation model on extracted values is investigated. In common with other EBIC approaches, this method is insensitive to changes in the diffusion length when the collection efficiency is high and diffusion lengths may not be reliably established in those cases.

This chapter explores how the University of New South Wales (UNSW) has undertaken silicon solar cell research since the mid-1970s and achieved world recognition in the 1980s. The UNSW solar cell research group has led international commercialisations and, since 2000, pioneered specialised undergraduate education in photovoltaics engineering. The Photovoltaics and Solar Energy undergraduate program is a unique four-year full-time Bachelor of Engineering program covering device theory; photovoltaic technology and manufacturing; photovoltaic applications and system design; policy, analysis, and modelling; renewable energy technologies; and sustainable energy. The related Renewable Energy Engineering program encompasses a broader range of renewable energy technologies including solar thermal systems, wind turbines, biomass, and also the important areas of solar architecture and energy efficiency. The School also offers four postgraduate coursework and two research programs in the same topics. In-house developed technical tools are used extensively in teaching and research.

In order to increase photocurrents of crystalline silicon solar cells through modification of the solar spectrum, we have investigated the upconversion effect of NaYF4:Er3+ nanocrystals. The upconverting layers of NaYF4:Er3+ nanocrystals were prepared by spin casting and post-soaking processes. The material characterization and the upconversion spectroscopy were carried out as functions of the erbium doping concentration and the film thickness. The effect of the laser density on the optimal ratio of trivalent erbium against trivalent yttrium has also been investigated using power dependent upconversion spectroscopy at various doping ratios. Through this study, optimized upconverting nanocrystals and fabrication methods to minimize the thickness of upconverting films have been investigated and achieved.

A new, analytical method is presented for calculating the depletion‐region recombination current for abrupt‐junction diodes under forward bias. The method is appropriate when the recombination current is dominated by recombination through Shockley–Read–Hall centers at a single energy level whose density does not vary strongly with position through the device. The new model is systematically compared with earlier models and with the results of finite‐element analyses using PC‐1D. If it is reasonably assumed that PC‐1D is the most accurate of the methods considered here, the others may be ranked according to their proximity to the PC‐1D result. It is shown that the new method, despite its simplicity, yields results closer to PC‐1D than the earlier models for many practical situations. In addition, it is shown that one existing model may be brought into agreement with the finite‐element analysis by a simple modification of the limits of integration.

Recent work has indicated that a significant number of electrons and holes remain in the free‐exciton form in silicon at room temperature, a finding which, if supportable by experimental evidence, requires the inclusion of excitons in diode and solar cell theory. Excitons, although neutral, may contribute to device currents by diffusing to the junction region where they may be dissociated by the field. A generalized three‐particle theory of transport in semiconductors is presented. The results of application of the theory to silicon devices indicate a decrease in the dark saturation current as well as an increase in light‐generated current when excitons are incorporated in the theory so long as exciton diffusion length exceeds that of the minority carriers. The work includes suggestions for experimental methods to confirm exciton involvement and to estimate the value of the exciton‐binding parameter from spectral response measurements on solar cells.

Crystalline silicon single quantum wells (QWs) were fabricated by high-temperature thermal oxidation of ELTRAN® (Epitaxial Layer TRANsfer) silicon-on-insulator (SOI) wafers. The Si layer thicknesses enclosed by thermal SiO2 range from 0.8 to 5 nm. Luminescence energies from such QWs vary from 1.77 to 1.35 eV depending on the Si layer thickness, without evidence for interface-mediated transition seen in earlier work. The ability to detect quantum-confined luminescence seems to arise from the use of ELTRAN SOI wafers, from suppressed interface state luminescence by high-temperature oxidation and, possibly, from interface matching by crystalline silicon oxide.

Due to its indirect bandstructure, bulk crystalline silicon is generally regarded as a poor light emitter. In contrast to this common perception, we report here on surprisingly large external photoluminescence quantum efficiencies of textured bulk crystalline silicon wafers of up to 10.2% at T=130 K and of 6.1% at room temperature. Using a theoretical model to calculate the escape probability for internally generated photons, we can conclude from these experimental figures that the radiative recombination probability or internal luminescence quantum efficiency exceeds 20% at room temperature.

Two competing theories of the optical absorption edge of intrinsic crystalline silicon, the indirect transition theory, and the recent disorder (Urbach edge) theory, are assessed critically. The assessment of the indirect transition theory includes an attempt to predict, by the use of the luminescence spectrum and the principle of detailed balance, the optical absorption in the wavelength range where it is mediated by the simultaneous absorption of up to three phonons. The inability of this method to accurately reproduce the experimental data is used to illustrate limitations of the indirect transition theory: its neglect of band degeneracy and its failure to explain the different absorption replica shapes for different phonons. In its published form, the disorder theory does not explicitly address the question of the role of indirect processes or the nature of the strong transitions which trigger the disorder processes. Some of the evidence presented in favor of the theory is shown to be in doubt. The possible synthesis of the two theories is proposed.