Major Research Areas
BURIED CONTACT AND OTHER COMMERCIAL SOLAR CELLS
J Cotter, S Wenham
UNSW has had considerable success in developing and commercialising photovoltaic technologies such as the buried contact solar cell, with licensees in many countries. A major program focuses on adapting the high performance attributes of UNSW's world record solar cells for use in low cost implementations suitable for commercial manufacturing.
LIFE CYCLE ANALYSIS OF RENEWABLE ENERGY SYSTEMS
M Watt
Life-cycle analysis involves the determination and consideration of the full life-cycle costs associated with the use of particular technologies. This is important when considering the cost of the generation of electricity by renewable energy systems.
LIGHT TRAPPING IN THIN CRYSTALLINE SILICON
J Cotter, S Wenham, M Green
Light-trapping in silicon refers to the use of certain structures for the silicon that are able to trap light within the silicon material as it repeatedly bounces between the front and rear surfaces. Light-trapping is particularly important in thin-film solar cells to effectively enhance the absorption of the semiconductor material by making it appear thicker than it really is. The concept of total internal reflection and the use of metal/other reflectors can be important in this research area.
N-TYPE SOLAR CELLS
J Cotter, S Wenham, M Green
P-type wafers have dominated commercial production for decades. In recent years however, improved understanding of boron-oxygen related defects in such wafers has led to growing importance being placed on developing new technology based on n-type wafers that do not suffer the same degradation mechanisms. A range of new cell fabrication approaches and design concepts are being explored and developed through this work with the aim of implementing and optimising high performance n-type wafer cell technology commercially throughout the world.
PHOTOVOLTAIC DEVICE AND MATERIAL CHARACTERISATION
A Sproul, A Aberle
UNSW has developed excellent device and material characterisation capabilities, which are used extensively within the photovoltaic device and technology development projects at UNSW.
PHOTOVOLTAIC MODULE DESIGN
S Wenham
The high cost of the photovoltaic devices relative to the encapsulation materials provides considerable incentive and opportunity to develop innovative module designs. Such designs can use reduced photovoltaic device area in conjunction with appropriate optics that collect and redirect light incident on adjacent regions to the solar cells, across to the solar cells. These are often referred to as static concentrators.
PHOTOVOLTAICS IN DEVELOPING COUNTRIES
A Sproul, R Corkish
This is a new research area at UNSW with the emphasis on the development and use of photovoltaic technology for improving the standard of living for those in developing countries. The research and educational activities in this area are closely linked with students from UNSW travelling each year to countries such as Nepal and Nicaragua to help with technology development, implementation and use. PV system design is also an important component of this work.
POWER GRID INTERACTION OF RENEWABLE ENERGY SYSTEMS
M Watt
Peak loads on power networks are extremely expensive for electricity suppliers to meet and there is a potentially important role for renewable energy, especially photovoltaics. This research stream explores the technical and economic issues associated with photovoltaics and electricity loads.
RENEWABLE ENERGY POLICY
M Watt
With rapidly growing renewable energy industries, many environmental concerns and government subsidy programs throughout the world, there is a growing importance being placed on renewable energy policy and legislative policy analysis.
SCREEN-PRINTED SOLAR CELLS
J Cotter, S Wenham
Screen-printed solar cell technology has dominated commercial markets for several decades. Despite the development and commercialisation of several new higher performance solar cell technologies, nothing has compared with the commercial dominance of screen-printing. Several new projects have correspondingly been established to overcome the fundamental performance limitations of screen-printed solar cells while retaining their simplicity, robustness, manufacturing equipment requirements and low cost.
SEMICONDUCTOR DEVICE MODELLING
M Green, A Sproul, S Wenham
UNSW has developed a particular strength in device modelling including through use of device modelling software such as PC1D. The strong device oriented experimental programs at UNSW provides the ideal environment for ongoing developments with device simulation and modelling software packages.
SILICON PHOTONICS
M Green, S Wenham, T Trupke
The Centre's work in silicon photonics, based on the fact that solar cells are very good emitters if operated in reverse mode, has two main thrusts. The first is to demonstrate silicon light emitters that can be integrated into silicon microelectronic circuits. The second is to investigate the feasibility of innovative schemes for demonstrating a silicon laser. A range of silicon optoelectronic characterisation activities underpins both these programs.
SILICON SOLAR CELLS
A Aberle, J Cotter, M Green, A Sproul, S Wenham
Approximately 90% of commercially manufactured solar cells are made from crystalline silicon. The majority of photovoltaic research at UNSW focuses on this type of device. UNSW has led the world in high performance silicon solar cells for more than a decade and has had considerable success developing commercially significant technologies based on these developments.
THIN FILM CRYSTALLINE SILICON PHOTOVOLTAIC DEVICES
A Aberle, M Green
Material costs strongly dominate for the conventional silicon wafer based photovoltaic technologies. In theory, with good light trapping and surface passivation it should be feasible to still achieve efficiencies well above 10% using crystalline silicon layers of only about 1% of the thickness of conventional wafers. This commercially relevant research area focuses on the development of such thin-film technologies and addresses, material, device performance, and manufacturing issues.
THIRD GENERATION PHOTOVOLTAICS
M Green, G Conibeer, R Corkish
First generation photovoltaics refer to the wafer based technologies, while second generation photovoltaic devices encompass all the thin-film technologies. The principal objective of the third generation research at the Centre is to significantly improve photovoltaic performance beyond that of present devices. Ultimately, it is anticipated that photovoltaic devices may use quite different concepts, materials and energy conversion processes, perhaps ones not even contemplated at this stage. Processes able to utilize the heat within the photovoltaic device are of particular interest. The fundamental research in this area may not realise actual devices for several years.
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Description of Laboratory Facilities
The Centre for Photovoltaic Engineering has established some of the best laboratory facilities internationally for silicon solar cell research. These include the Photovoltaics Research Laboratories, the Device Characterisation Laboratory, the Optoelectronic Research area, the Thin-Film Cell Laboratory, an Industry Collaborative Laboratory, and a Thin-Film Cleanroom facility at Botany. The Centre also owns equipment within, and has access to, the Semiconductor Nanofabrication Facility (SNF) at the University.
Photovoltaics Research Laboratories
This is the largest and most sophisticated bulk silicon solar cell research facility in Australia, and incorporates both the High Efficiency / LED and Buried Contact Cell Laboratories. The laboratories are furnished with a range of processing and characterisation equipment including 26 diffusion furnaces, 6 vacuum evaporation deposition systems, 2 laser-scribing machines, rapid thermal annealer, four-point sheet-resistivity probe, quartz tube washer, silver, nickel and copper plating units, infrared and visible wavelength microscopes, 3 wafer mask aligners, spin-on diffusion system, automated photoresist dual-track coater, photoresist spinner, electron beam deposition system, TiO2 spray deposition, belt furnace, manual screen printer and a laboratory system control and data acquisition monitoring system.
Device Characterisation Laboratory
The Device Characterization Laboratory houses characterisation equipment including "Dark Star", the Centre's station for temperature controlled dark current-voltage measurements, the Centre's Fourier-transform infrared spectroscopy system (FTIR), admittance spectroscopy system, microwave carrier lifetime system, ellipsometer, photo conductance decay equipment, wafer probing station for SOI LED work, open circuit voltage decay measurement system (Suns-Voc)infrared microscope and equipment for spectral response and related optical measurements.
Optoelectronic Research Area
This facility is used for photoluminescence and electroluminescence measurements in the visible and infrared spectral range up to wavelengths of 2500nm; photoluminescence excitation spectroscopy; luminescence experiments with simultaneous two-colour illumination and Sinton lifetime testing with the conventional flash-light replaced by a high-power light emitting diode array. It has several visible and near-infrared semiconductor diode lasers and optical and electrical instrumentation.
Thin Film Cell Laboratory
The Thin Film Cell Laboratory is equipped with a range of equipment for thin-film deposition and patterning, including a plasma-enhanced chemical vapour deposition (PECVD) system, a sputtering system, a reactive ion etcher, a resistively heated vacuum evaporator, and an optical microscope with digital image acquisition system. Also used by the Laboratory is an electron-beam vacuum evaporator for silicon physically located within the Photovoltaics Research Laboratories.
Semiconductor Nanofabrication Facility
The Centre also owns equipment within, and has access to, the Semiconductor Nanofabrication Facility (SNF) at the University. This is a joint facility shared by the Faculties of Science and Engineering and houses a microelectronics laboratory and a nanofabrication laboratory for e beam lithography.
Industry Collaborative Laboratory
This 120-m2-laboratory houses equipment needed for many of the industry-collaborative research activities in the Buried-Contact Solar Cell group. The laboratory was refurbished in 1999 and several new pieces of infrastructure have been acquired or constructed since, including: a belt furnace; a state of the art laser micro machining tool; and a TiO2 spray deposition station. In 2004 a high temperature semiconductor muffle furnace was added along with the commissioning of a manual screen printer whilst the group awaits delivery of their production screen-printing unit.
Cleanroom facility Bay Street, Botany
This recently acquired cleanroom facility has greatly improved the Centre's experimental capabilities in the area of thin-films. This cleanroom is equipped with several fume cupboards, two tube furnaces, an electron-beam vacuum evaporator, a thermal vacuum evaporator, a glass washing machine, a rapid thermal processing (RTP) machine, a 5-chamber cluster tool, a low pressure chemical vapour deposition (LPCVD) system, an infrared NdYAG laser scriber, and a box furnace for sample annealing.
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Further Information
Postgraduate Research Coordinator
Key Centre for Photovoltaics & Solar Energy
Dr Alistair Sproul
Phone: +61 2 9385 4039
Fax: +61 2 9385 7762
Email: a.sproul@unsw.edu.au
Website: http://www.pv.unsw.edu.au
