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Credit Link - http://www.abc.net.au/news/2016-08-20/solar-energy-and-panels-explained/7763474Solar cell technology: How it works and the future of sunshine
How do solar cells work?
At the heart of a solar cell is a tiny electric field that splits negative charges from positive charges using the energy of sunlight.
What will solar cells look like in 20 years' time?
In 20 years' time the solar panels on your roof will probably look the same as now with their aluminium frame and glass front, but they will likely be a whole lot cheaper and at least half again as efficient thanks to smart engineering.
A range of new technologies being researched now in labs across Australia and the world may overcome the efficiency limits of silicon-only solar cells.
One of the exciting developments in the field is a new semiconductor called "methyl ammonium lead iodide perovskite".
Solar cells made out of this cheap and easy to produce material have already achieved 20 per cent efficiency in the lab — matching the efficiency of today's silicon cells.
In the future, perovskites may either replace silicon solar cells or be used as a companion material to help them move beyond 26 per cent efficiency — the upper limit of silicon-only cells.
The research team I am part of at Monash University and CSIRO is experimenting using perovskites as the top layer in double-decker "tandem" solar cells that absorb different colours of sunlight in each layer.
In a tandem solar cell, high-energy photons (green, blue and UV) are absorbed in the top layer, and low-energy photons (red, orange and yellow) are absorbed in the bottom layer. This allows the solar cell to squeeze more energy out of sunlight — we are aiming for double the efficiency of rooftop solar cells at super low cost.
Other ideas being pursued around Australia and the world include reflected-tandems (double-decker solar cells placed side by side), quantum-dot solar cells (using tiny nanocrystals as the energy absorber material), up-conversion of light (converting two low-energy photons, that would otherwise be wasted, to make one high-energy photon) and hot-carrier cells (collecting charge from solar cells before they have the chance to lose any voltage).
It is not too hard to imagine a future with thin, efficient, lightweight and flexible solar cells on mobile phone cases, laptop bags, backpacks, suitcases, hats, tents, you name it…
How 'green' are solar cells?
It takes about two to five years for a solar panel to "pay back" the energy that went into making them (depending on how sunny it is where you live). This includes the energy needed to mine the silicon and process it into a solar cell, and also make the aluminium frame and glass in the panel module housing.
Solar panels usually come with a guarantee of 80 per cent output for 25 years (and there is no reason why they should not last longer), which means energy-wise solar panels are a good thing, by a factor of at least four.
Silicon is the second most abundant element in the Earth's crust (second to oxygen in the silicon dioxide that makes up sand and quartz), so there will not be any material shortages in the foreseeable future.
Solar panel recycling stations are starting to be set up all over the world — like aluminium recycling, silicon is an excellent candidate for cradle-to-grave-to-cradle material management.
And sunshine itself is the most sustainable resource we have — the sun should be around for a few more billion years at least.
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