Need of New Solar cell technology
Food, shelter and cloths are the primary needs of the man-kind. Industrial and agricultural revolutions, occurred at regular intervals, made human race fulfill its basic needs. These revolutions were backed by a solid thought process of intelligent minds. Minds those were freedom-lovers, knowledge persuasive and hungry for development. Most of the nations got their freedom in 20th century and soon became developing or developed nation. Their goal was to achieve prosperity, stability and sustainability.
To accomplish this socio-economic revolution, technology played a crucial part. Developments in technology, either analog or digital, transformed the nations from underdeveloped stage to developed ones. Transfer of labor, brain-drain, and emergence of new markets changed the course of economy and history. Each activity in every development sector was supported with strong sources of Energy like oil and coal. Energy was the real boost of whole system and access to energy became the mantra of 21st century. However, soon the system realized that it is resting on the support of non-renewable conventional energy sources, which are depleting at an alarming rate. The damage done by these polluting energy sources in terms of global warming, added to the urgency of discovery of alternative energy sources.
The requirements from the new source of energy were obvious – clean, continuous and renewable. It was realized that such sources are readily available and are naturally occuring. Phenomenon occurring in Mother Nature was the answer for virtually infinite sources of energy. It was realized that solar radiation, forces of winds and thermal gradients has the potential to fulfill all the requirements to become natural and prolific sources of energy. Efficient technologies were needed to tap this potential and convert them to useful form of energy. Intensive research and development program carried all over the world invented technologies like wind-mills, geothermal generation, tidal generation, bio-fuels, solar thermal and solar photovoltaic (PV). Solar PV soon becomes a technology to look for as an alternative source of energy supply. This was possible because of following reasons:
- Availability of sun’s energy, virtually infinite,
- Discovery of PV effect, showing the way to convert solar energy to flexible electrical energy,
- Realization of solar cells for using it for a wide capacity of electricity production,
- Continuous developments in PV technology, aiming to increase efficiency while reducing the per-unit cost of electricity, and
- Established Silicon (Si) IC technology – makes enable to transfer knowledge from IC manufacturing industry to solar PV production industry.
Need for new solar cell technology
The shift of the solar cell market from a supply-restricted to a demand-driven market has altered the economics of the trend. To maintain enormous sensation in worldwide PV production to meet future demands, different path ways have to be pursued. Few promising pathways are:
- expanding solar grade Si production capacities
- reduction in material consumption
- accelerated thin-film solar cell manufacturing
The concept of ‘third generation PV’ is to significantly enhance device efficiency (more than single junction cell efficiency) using thin film processes and by using abundant non-toxic materials. Conversion efficiency is one of the influential parameter for implementing PV cells on a truly large scale. High conversion efficiency can significantly bring down the solar PV energy conversion cost. The maximum thermodynamic efficiency for the conversion of non-concentrated solar irradiance into electrical energy for single junction was calculated by Shockley and Queissar to be about 31%. General approaches to achieve efficiency higher than Shockley-Queissar limit consists of exploiting entire solar spectrum, modification in solar spectrum and reduction in thermal losses. As single junction or classical approach cannot overcome this limit, several new approaches to outwit the Shockley–Queissar limit under active investigation includes tandem cells, hot carrier solar cells, multiband and impurity solar cells.
(to be continued....)
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