Matt Stocks

Australian National University | ANU · Centre for Sustainable Energy Systems

Rapid cost reductions of solar photovoltaics and wind offer a pathway to deep decarbonization of energy at low cost. Off-river pumped hydro energy storage provides mature, cheap and very large-scale storage that helps to balance variable generation and demand while avoiding environmental and social impacts. Many developing countries, especially tho...

Achieving the goal of net zero emissions targeted by many governments and businesses around the world will require an economical zero-emissions fuel, such as hydrogen. Currently, the high production cost of zero emission ‘renewable’ hydrogen, produced from electrolysis powered by renewable electricity, is hindering its adoption. In this paper, we e...

Low-cost solar photovoltaics and wind offer a reliable and affordable pathway to deep decarbonization of energy, which accounts for three quarters of global emissions. However, large-scale deployment of solar photovoltaics and wind requires space and may be challenging for countries with dense population and high per capita energy consumption. This...

The Asia-Pacific has experienced prodigious growth in energy use and is by far the world's largest greenhouse-gas emitting region. Australia has played a leading role in meeting the region's energy and resource needs, becoming the world's largest exporter of coal, liquefied natural gas, iron ore, and alumina. Our analysis shows that these exports a...

This study considers the emissions implications of co-combusting imported ammonia in coal-fired power stations. The study adopts a supply chain approach, estimating the emissions reduction potential of 20% ammonia co-combustion in coal-fired power stations in the country of use, and the emissions associated with ammonia production in the country of...

Large greenhouse gas reductions are possible with a fully decarbonised grid and electric land transport. Additional electric load could pose a significant challenge to a grid with high levels of variable and non-dispatchable renewable energy sources. This scenario is not well-examined, nor is the use of pumped hydro energy storage for low-cost ener...

Japan has committed to carbon neutrality by 2050. Emissions from the electricity sector amount to 42% of the total. Solar photovoltaics (PV) and wind comprise three quarters of global net capacity additions because of low and falling prices. This provides an opportunity for Japan to make large reductions in emissions while also reducing its depende...

In this paper, we conclude that Indonesia has vast potential for generating and balancing solar photovoltaic (PV) energy to meet future energy needs at a competitive cost. We systematically analyse renewable energy potential in Indonesia. Solar PV is identified to be an energy source whose technical, environmental and economic potential far exceeds...

Rapid increases in electricity consumption in Southeast Asia caused by rising living standards and population raise concerns about energy security, affordability and environmental sustainability. In this study, the role of short-term off-river energy storage (STORES) in supporting 100% renewable electricity in Southeast Asia is investigated. Lar...

High levels of variable solar and wind must be balanced with alternative generation, storage, transmission and demand management to ensure continuous availability of electricity. The cost of balancing has been disputed, which militates against mass deployment of solar and wind to mitigate climate change. Australia is installing solar and wind 10 ti...

Surface texturing of a silicon solar cell is critical to provide surface antireflection and light trapping. The common texturing method based on KOH as an etchant with isopropyl alcohol (IPA) as a wetting agent suffers two disadvantages: introducing metal contamination and low repeatability. To circumvent the limitation of the KOH-IPA method, we de...

The need for storage in electricity systems is increasing because large amounts of variable solar and wind generation capacity are being deployed. About two thirds of net global annual power capacity additions are solar and wind. Pumped hydro energy storage (PHES) comprises about 96% of global storage power capacity and 99% of global storage energy...

Accurate long-term wind speed data is important for understanding the role of offshore wind farms in future energy systems. Meteorological reanalyses, such as ERA5, are relied upon by the wind energy industry and researchers. Being unaffected by onshore topography and surface roughness, the historic generation of offshore wind farms can be accurate...

Thanks to fast learning and sustained growth, solar photovoltaics (PV) is today a highly cost-competitive technology, ready to contribute substantially to CO 2 emissions mitigation. However, many scenarios assessing global decarbonization pathways, either based on integrated assessment models or partial-equilibrium models, fail to identify the key...

Australia has one of the highest per capita consumption of energy and emissions of greenhouse gases in the world. It is also the global leader in rapid per capita annual deployment of new solar and wind energy, which is causing the country’s emissions to decline. Australia is located at low-moderate latitudes along with three quarters of the world’...

The difficulty of finding suitable sites for dams on rivers, including the associated environmental challenges, has caused many analysts to assume that pumped hydro energy storage has limited further opportunities to support variable renewable generation. Closed-loop, off-river pumped hydro energy storage overcomes many of the barriers. Small (squa...

We study the greenhouse gas emissions of different technology choices for ammonia production for power generation. We adopt a global supply chain approach, considering emissions generated at the point of manufacture in addition to consumption for ammonia co-combustion in coal fired power stations using a range of ammonia production technologies. Th...

Adv. Energy Mater. 2020, 10, 1903553 In the original manuscript, the spelling “Anita Ho-Ballie” is incorrect. The correct spelling is, “Anita Ho-Baillie” The authors apologize for any inconvenience caused.

Australia has one of the highest per capita consumption of energy and emissions of greenhouse gases in the world. It is also the global leader in rapid per capita annual deployment of new solar and wind energy, which is causing the country's emissions to decline. Australia is located at low-moderate latitudes along with three quarters of the global...

This work presents results of a laboratory‐scale interdigitated back contact (IBC) solar cell with an independently measured efficiency of 25.0%, featuring open‐circuit voltage of 716 mV, short‐circuit current of 43.0 mA.cm⁻² and fill factor of 81.0%. Notably, the high efficiency was achieved based on significant improvements resulting from the opt...

Titania (TiO $_{\rm x}$ ) is re-emerging to be a passivating material for the surfaces of high-efficiency crystalline silicon solar cells. Numerous sources in the literature suggest that the surface passivation and thermal stability of TiO $_{\rm x}$ deteriorates with increasing film thickness when the TiO $_{\rm x}$ film is thicker than a suffi...

Mixed‐dimensional perovskite solar cells combining 3D and 2D perovskites have recently attracted wide interest owing to improved device efficiency and stability. Yet, it remains unclear which method of combining 3D and 2D perovskites works best to obtain a mixed‐dimensional system with the advantages of both types. To address this, different strate...

Deep etched structures in GaAs have many applications in optoelectronics and MEMS devices. These applications often require an anisotropic etch profile with smooth sidewalls as well as a high etch rate and high aspect ratio. Developing an etch process that demonstrates high selectivity for the etch mask is critical as etch times for deep grooves ca...

Rapid cost reductions have led to the widespread deployment of renewable technologies such as solar photovoltaics (PV) and wind globally. Additional storage is needed when the share of solar PV and wind in electricity production rises to 50-100%. Pumped hydro energy storage constitutes 97% of the global capacity of stored power and over 99% of stor...

Solar photovoltaics (PVs) and wind constitute more than 60% of global annual net new capacity additions. Balancing an electricity system with 30–100% variable PV and wind is straightforward using off-the-shelf techniques comprising stronger interconnection over large areas to smooth out local weather, storage, demand management, and occasional spil...

We investigate the versatility of anodically grown silicon dioxide (SiO 2) films in the context of process durability and exceptional surface passivation for high efficiency (> 23%) silicon solar cell architectures. We show that a room temperature anodic oxidation can achieve a thickness of ~70 nm within ~30 min, comparable to the growth rate of a...

As silicon photovoltaic technology advances, charge carrier losses at the contacted interfaces of the silicon absorber are coming to dominate power conversion efficiency. The so-called passivated contact, which provides selective charge-carrier extraction while simultaneously reducing interface recombination, is thus of significant interest for nex...

Silicon solar cells incorporating double-sided pyramidal texture are capable of superior light trapping over cells with front-side only texture. However, increased surface area, roughness and exposed <111> crystal planes of textured surfaces not only causes increased recombination, but also makes cells susceptible to shunting through pinholes in th...

Immeasurably low surface recombination of crystalline-silicon wafers is demonstrated with an oxide-nitride-oxide (ONO) corona charged dielectric stack. We detail experimental variations to each layer of the dielectric stack to establish a procedure which provides outstanding passivation properties on textured and planar silicon wafers. We demonstra...

Pumped hydro energy storage is capable of large-scale energy time shifting and a range of ancillary services, which can facilitate high levels of photovoltaics and wind integration in electricity grids. This study aims to develop a series of advanced Geographic Information System algorithms to locate prospective sites for off-river pumped hydro acr...

Silicon solar cells incorporating double-sided pyramidal texture are capable of superior light trapping over cells with front-side only texture. However, increased surface area, roughness and exposed < 111 > crystal planes of textured surfaces not only causes increased recombination, but also makes cells susceptible to shunting through pinholes in...

Methods • The site searching methodology involves applying search criteria to land areas with elevation differences greater than 300m (or 200m for WA, NT and SA) and outside of protected and urban areas Introduction • As wind and PV energy generation extends into the 50-100% range over the next decade, a combination of additional interstate high vo...

We investigate the light trapping in Si wafers that are textured with conventional random pyramids on their front surface and rounded random pyramids on their rear. It is well established that rounding the pyramids leads to better surface passivation, but whether or not it improves light trapping depends on the cell structure. In this paper, we app...

An hourly energy balance analysis is presented of the Australian National Electricity Market in a 100% renewable energy scenario, in which wind and photovoltaics (PV) provides about 90% of the annual electricity demand and existing hydroelectricity and biomass provides the balance. Heroic assumptions about future technology development are avoided...

Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4%. The study shows the beneficial effect of Rb in improving the crystallinity and suppressing...

We analyze the potential benefits for behind-the-meter PV/battery systems of wholesale energy market participation in the Australian energy market. Using historic energy market price and demand data we show that PV / battery systems have the potential for significant financial benefit if operated so as to export during periods of peak wholesale pri...

Rapidly increasing penetration of renewables, primarily wind and photovoltaics (PV), is causing a move away from fossil fuel in the Australian electric power industry. This study focuses on the South West Interconnected System in Western Australia. Several high (90% and 100%) renewables penetration scenarios have been modelled, comprising wind and...

A tandem configuration of perovskite and silicon solar cells is a promising way to achieve high-efficiency solar energy conversion at low cost. Four-terminal tandems, in which each cell is connected independently, avoid the need for current matching between the top and bottom cells, giving greater design flexibility. In a four-terminal tandem, the...

The contact resistivity of evaporated Al on doped silicon is examined for a range of process conditions common to the fabrication of laboratory silicon solar cells. The effects of silicon surface preparation prior to evaporation, sintering temperature, the use of a shutter, and evaporation power are investigated. The presented evaporation condition...

A new dielectric totally internally reflecting concentrator (DTIRC) design has been developed for use with bifacial photovoltaic cells. The structure incorporates the bifacial cell standing vertically at the base of the structure, immersed in dielectric. DTIRC structures with single-sided photovoltaic receivers, like CPC structures, are designed us...

We study a spectral-splitting perovskite-silicon tandem concept where the perovskite cell provides selective reflection of long wavelength light. Minimizing parasitic optical losses can lead to 2% efficiency gains, and tandem efficiencies of >26%.

Metal-assisted chemical etching (MACE) is an inexpensive, simple method for etching silicon structures, including the etching of high aspect ratio grooves. We improve on the best reported results in this area by etching grooves with aspect ratios of 65 (vertical depths 650 µm) in n-type silicon. The grooves maintain an excellent degree of verticali...

A procedure to quantify the optical loss mechanisms in back-contact solar cells is presented. It incorporates recent developments in optical simulation that yield rapid and precise results. The procedure includes spectrophotometry, ellipsometry, quantum efficiency measurements, ray tracing, and the thin-film matrix method. The paper shows how exper...

The interdigitated back contact (IBC) solar cells developed at the Australian National University have resulted in an independently confirmed (Fraunhofer Institut für Solare Energiesysteme (ISE) CalLab) designated-area efficiency of 24.4 ± 0.7%, featuring short-circuit current density of 41.95 mA/cm2, open-circuit voltage of 703 mV and 82.7% fill f...

A new technique for producing thin single-crystal silicon solar cells has been developed. The new technology allows for large decreases in silicon usage by a factor of 12 (including kerf losses) compared to conventional crystalline silicon wafer technologies. The new Sliver® cell process uses a micromachining technique to form 60 μm-thick solar cel...

Texturing has enabled the manufacture of SLIVER cells with efficiencies in excess of 19% and boosts in SLIVER module performance of 16%. The improvement was due to reduced reflection losses and improved light trapping. Excellent texturing results could also be expected on multicrystalline silicon wafers due to the isotropic nature of the texturing...

SLIVER modules differ significantly from conventional crystalline silicon modules due to the unique geometry and performance of SLIVER solar cells. This offers many performance advantages including excellent resistance to shading, low temperature coefficient and flexible output characteristics while demonstrating good robustness during reliability...

The paper presents an update on the development of the new SLIVER solar cell and module technology. The SLIVER technology uses micromachining techniques to fabricate 50-micron thin monocrystalline silicon solar cells. Due to their design and fabrication process, the SLIVER cells are bifacial and exhibit the efficiency and the performance stability...

This letter presents a new process for the fabrication of solar cells and modules from single crystal silicon wafers with substantially reduced silicon consumption and processing effort compared to conventional wafer-based cells. The technique of narrow trench etching in an alkaline solution is used to create a series of thin silicon strips extendi...

Sliver cells, invented and developed at The Australian National University, are long, thin, narrow, and bifacial. They are constructed from high-grade mono-crystalline silicon. Solar modules that incorporate Sliver cells are significantly different in their construction and performance characteristics to conventional crystalline silicon modules....

A new technique has been devised for the manufacture of thin (

We present a new concept for thin silicon solar cells. In the LASE process (Lateral Anisotropic Silicon Etching) shallow grooves are cut into a (111) oriented silicon wafer at regular intervals. Using alkaline etching, lateral channels are formed which extend underneath the silicon wafer and eventually meet to detach the silicon layer on top. Unlik...

Silicon liquid phase epitaxy (LPE) is a suitable silicon deposition process for the fabrication of thin film silicon solar cells. In this paper we discuss the design and operation of a batch LPE system which is a first step towards mass production. The issue of melt cost can be addressed by efficient recovery of the melt and by switching to more wi...

The epilift technique allows the growth and detachment of good quality, single crystal silicon films on silicon substrates. Since the substrates only act as a growth template, they can be re-used, offering the potential for substantial cost reductions. However, the processing of solar cells on epilift layers introduces significant challenges as a r...

Thin (<70 micron) single crystal silicon solar cells have been manufactured through the use of a novel process involving selective etching. Narrow grooves are micromachined through the wafer using a standard micromachining technique with cells manufactured on the resulting silicon strips. These bifacial cells have a much greater surface area than t...

A significant reduction in contact resistance of palladium/silicon contacts was realised by the use of a thin intermediate gallium layer. The contact resistance of the palladium/gallium/silicon contact was found to be similar to aluminium/silicon contacts on 0.5 Ω cm silicon. Solar cells processed on 1 Ω cm substrates with this structure demonstrat...

Minority carrier recombination and trapping frequently coexist in multicrystalline silicon (mc-Si), with the latter effect obscuring both transient and steady-state measurements of the photoconductance. In this paper, the injection dependence of the measured lifetime is studied to gain insight into these physical mechanisms. A theoretical model for...

Thin-film silicon cells produced on crystalline silicon substrates have the potential to achieve high cell efficiencies at low cost. We have used a modified liquid-phase epitaxy growth process to produce very smooth, high-quality silicon films on multicrystalline silicon substrates. Photoconductivity decay measurements indicate that the minority ca...

The main applications of photoconductance measurements of silicon wafers are the determination of implicit device voltages, bulk minority carrier lifetimes, emitter recombination currents and surface recombination velocities. These applications are illustrated with selected experiments. Multicrystalline and single crystal silicon wafers are used wi...

The electronic quality of multicrystalline material produced by directional solidification has been evaluated by means of photoconductance techniques. Very high minority carrier lifetimes, in the vicinity of 200 μs, have been measured in p-type 1.5 Ω cm material that had received a phosphorus diffusion gettering treatment. The measurements correspo...

Multicrystalline silicon (mcSi) solar cell efficiency is primarily influenced by minority carrier lifetime of the material. Lifetimes in mcSi vary strongly during processing. Step by step monitoring has allowed identification of both beneficial and poor processing steps and lead to rapid improvements in cell efficiency. Phosphorous gettering signif...

Liquid Phase Epitaxy (LPE) is a suitable technique for the growth of thin silicon films for photovoltaics, offering low growth temperatures, high utilisation of silicon, and low cost and complexity. Former modelling results showed that it should be possible to reach efficiencies in excess of 18% although using an opaque as a substrate and no light...

Improvements in the manufacture of multicrystalline silicon (mc-Si) and processing induced impurity gettering have enabled the demonstration of diffusion lengths in mc-Si much greater than the substrate thickness. High recombination velocities at the rear surface, rather than bulk recombination, can then limit cell efficiency. The traditional n+/p/...

Multicrystalline silicon (mc-Si) solar cell efficiency is strongly related to the bulk material lifetime due to the low electronic quality. The minority carrier lifetime of multicrystalline silicon can vary greatly during the high temperature furnace steps involved in cell processing. Quasi-steady state photoconductance (QssPc) measurements were us...

We have developed a technique which allows the fabrication of single crystalline layers of silicon of arbitrary size and shape and with a thickness ranging from less than 50 to greater than 100 μm. The films are grown by liquid phase epitaxy (LPE) on single crystal silicon substrates which have been patterned with a suitable masking layer material...

A wet isotropic etching technique (“tubs”) has been developed for texturing polycrystalline silicon solar cells. Reflection losses are reduced by using total internal reflection from a glass encapsulant layer. The texture developed shows excellent reflection results, equivalent to microgrooves or inverted pyramids on encapsulated single crystal sub...

Thin solar cells based on low-quality silicon are assessed for a range of possible material parameter values and device structures. Device thickness is freely optimized for maximum efficiency for a range of doping densities and numbers of junctions, le ading to results differing markedly from previous investigations. Modelling of conventional and m...

Thin film silicon solar cells are attracting considerable interest as a possible means of achieving low cost while maintaining moderate to high cell efficiencies. In this paper we report on the results of our work to fabricate high efficiency cells on single crystal epitaxial layers. We use liquid phase epitaxy (LPE) to grow epitaxial layers of 30-...

A simple texturing procedure suitable for polycrystalline solar cells is described that matches the performance of anisotropic etching on single crystal wafers. Single crystal wafers are typically etched with anisotropic etches relying on knowledge of crystal orientation not possible with the random grain orientation in polycrystalline silicon. Sol...

Thin-film silicon solar cells are promising candidates for meeting the requirements of high efficiency combined with low cost. We use liquid-phase epitaxy to grow thin silicon films on highly doped substrates. A solar cell made on this material has been measured independently to have an efficiency of 17.0%. an important step in obtaining these high...