A solar cell is used to convert solar energy into electricity so that the sun’s power can be used by humankind. Solar cells are made of various materials. They capture the sun’s heat and convert it into electricity. The efficiency with which it this done is referred to as the efficiency of solar energy.

Solar energy itself is absolutely efficient. It does not produce any pollutants as by products and is a renewable source of energy. It can be captured either passively or actively.

The passive use of solar energy includes the use of south facing windows to capture solar light and heat. The drying of clothes on a clothes line is also another example of the passive use of solar energy.

In the attempt to actively harness the sun’s energy, photovoltaic cells come first. These cells are used to heat water for household consumption and to generate electricity for use in homes and offices. Other tools such are solar cookers are also considered active users of solar energy.

Initially, the first solar cells or photo voltaic cells were only 1 per cent efficient, that is, they converted only 1 per cent of the sun’s heat falling on them into electricity. This made them uncompetitive as a source of electricity especially in an era when coal power was inexpensive.

Later, with the improvements in science and technology, solar cells’ efficiency also improved. It is considered commonly that there are three generations of solar cells.

The first generation cells were single junction devices and had a limiting efficiency of 31 per cent with an energy pay back period of five to seven years. They were very labor-intensive to construct as well.

Second generation cells are less labor intensive to manufacture. Manufacturing techniques now incorporated solution deposition, vapor deposition, electroplating, and ultrasonic nozzles. These technologies also offer higher conversion efficiencies.

The third generation of cells hold the promise of improving the electrical performance of second generation cells while at the same time maintaining the low production costs. High energy conversion efficiencies can be achieved by multi-junction photovoltaic cells, concentration of the incident spectrum, the use of thermal generation by UV light to enhancer voltage collection, and the use of infrared spectrum for night time use.

High-efficiency solar cells can generate more electricity per incident solar power unit (watt/watt). The challenge of increasing photovoltaic efficiency is of great interest from both the academic and economic point of view. Multiple-junction solar cells have an efficiency of over 40 per cent.

Thin-film solar cells have an efficiency of over 18 per cent in turning solar power into electricity.

The latest technology in the field of solar energy uses nano flakes. These nano flakes promise to revolutionize the process of generation electricity from the sun’s energy. They are likely to be viable and help improve the record for producing clean energy from the sun. These future solar cells are expected to have a 30 per cent efficiency rate that is twice that of the average photo voltaic cells used today.

Discovered by Martin Aagesan who has found a new and untried material, the nano flakes are all set to revolutionize the technology. He discovered a perfect crystalline structure that also absorbed all light. Thus it has the potential to become the perfect solar cell. These cells are expected to reduce the cost of production of the nano flakes and also exploit the energy of the sun more effectively, thereby lessening the loss of energy.

There are two components to increasing the efficiency of photovoltaic cells. One is reducing the cost of manufacture of the cells themselves. The other is to increase the efficiency of individual cells so that they can produce more electricity per cell. Both these methods are being pursued by corporations and scientists alike in a bid to both lower the total costs of solar energy and to increase the power generated by the cells. The cost per unit of electricity generated using solar cells is thus expected to come down gradually in the future.

Another way of reducing your power bills is to have a green home. This is possible by insulting the attic and caulking all the doors and windows. Letting in the warm sun from the south side of the home and shutting the north side so that cold air does not come in can also save on electricity bills. Similarly, during the summer months, one should keep the north facing windows open and shut the south facing ones. These measures too will save on electricity bills while using the sun’s energy in a passive yet intelligent way.

Yet another way of increasing the power generated by solar cells is to use concentration methods to focus the sun’s energy on the photovoltaic cells. This can be done using mirrors to reflect and concentrate sunlight onto receivers that convert it into heat energy. This heat is then used to power turbines. This is a highly efficient method of converting solar heat energy into electricity. Large solar `farms’ are constructed for this purpose.

A combination of all the technologies described above can be used to utilize solar energy efficiently and in a cost effective manner. The technologies and systems need to be used depending on the location and nature of the building. The purpose of the building also needs to be kept in mind for this.

Homes typically can use photovoltaic cells as they can easily be mounted on roofs or walls. New technology will soon permit the printing of photovoltaic cells that can then be pasted on to roofs and walls. This will not only reduce initial material costs but also the cost of labor and the cost of making the house structurally sound enough to support an array of solar panels on the roof or walls. This too will reduce the cost per unit of electricity generated using the sun’s heat.

Newer technologies are bound to come up that increase the efficiency of generating electricity using the sun’s heat. Both corporations and scientists are working toward this goal.