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| CSIRO | SOLVE | Issue 11 | MAY 07 | |
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ARTICLE
By Robin Taylor
Researchers are developing technologies to replace silicon with plastic in a wide range of electronics, which will use energy much more efficiently.We all use curtains in our homes to keep out sunlight on hot days. However, scientists pose the question: why not put this energy to use and replace curtains with material-like solar cells to generate electricity? It is a scenario that is becoming possible through the development of large-area, flexible solar cells, and comes from emerging technologies that may allow silicon (the conventional solar cell material) to be replaced by plastics. At CSIRO Molecular and Health Technologies, researchers are using plastic (polymer) electronics in a number of areas such as the fabrication of flexible solar cells and display screens. Although polymers are usually thought of as insulators, some types of polymers can conduct electricity. Polymer electronics is about using these semi-conducting polymers to replace inorganic conductors such as silicon in a variety of applications. The advantages are that polymers are cheap, easily processed, light and flexible.
CSIRO researcher Dr Scott Watkins says plastic electronics have the potential to produce big advances on a number of fronts. “It will enable new technologies, such as roll-up TVs, more efficient generation of electricity through cheaper solar cells and more efficient use of energy,” he says. “Polymer-based lighting also has the potential to be even more efficient than fluorescent lights.” CSIRO’s input is to design and synthesise polymers with controlled structures on a nanoscale. This controls how charges (electricity) flow through the polymer films to maximise their performance. One application that CSIRO and others are pursuing is the use of polymers as light-emitting materials in displays for appliances such as laptops, televisions and mobile phones. “They are more efficient at turning electricity into light than existing LCD and plasma displays, and the device structures are simpler and thus should be cheaper to produce,” Dr Watkins says. “Also, brighter colours, higher contrast and better viewing angles mean easier-to-read displays, even in full sunlight.” Light-emitting polymers developed by others have already been commercialised in small devices. Cambridge Display Technology (CDT) was formed by a group at Cambridge University that discovered light-emitting polymers in the early 1990s. CDT has licensed the technology to manufacturers such as Philips, and simple displays have appeared in mobile phones and shavers. Other display manufacturers have also demonstrated prototype devices. “In a typical organic light-emitting diode (OLED) device a thin film of polymer – like a chip packet but less than 100 nanometers thick – is sandwiched between two electrodes, one of which is transparent,” Dr Watkins explains. “When a voltage is applied across the electrodes the polymer emits light. Extra layers can be added to make the devices more efficient. “The remaining challenges to widespread commercial adoption of the technology are advances in device lifetimes and efficiencies. Significant progress has been made in improving devices in the lab, but these improvements remain to be proved on a production line. The key is developing the right polymers and the right device structures.” The other area of potential for plastic electronics, one that is a little further away from being a commercial reality, is low-cost solar panels made of polymeric materials. Being much cheaper to produce than silicon solar cells, polymeric films have the potential to be larger and more readily available. Like their light-emitting analogues, the active component of polymer solar cells is only about 200 nm thick and can be deposited directly onto plastic. Huge rolls of power-generating polymer could feasibly be used to supply energy efficiently and cleanly. In the case of polymer solar cells, the demonstration of reasonable efficiencies (5 to 10 per cent) in prototype devices is the first step. Longevity is obviously also a key concern.
“Given that companies such as CDT have increased the lifetimes of their light-emitting polymer device from one to more than 100,000 hours over the past few years, the prospects for similar improvements in polymer solar cells are good,” Dr Watkins says. “The ultimate goal is to move from the relatively crude polymer blends to new, engineered polymers that will realise the dream of large-area flexible solar panels. “Locally, we are pursuing links with printing and building material manufacturers who are attracted to the concept of films of solar cells. CSIRO is also part of a consortium that has just received a $12 million grant to develop advanced materials for organic solar cells. There are real opportunities for Australian industry to lead the world in the commercialisation of this technology.” For further information contact: |
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