The low-cost solar cell is an effort to make solar power price competive with traditional (fossil fuels and nuclear power) energy sources.

The polysilicon shortage^[1]has changed the economics, making technologies such as thin films, which use little or no silicon, more attractive.^[1] The cost per watt will be the determining factor for success.^[1] The solar industry can potentially reduce costs 40 percent over the next five years as the silicon shortage ends.^[1][2]

Grid parity, the point at which photovoltaic electricity is equal to or cheaper than grid power can be reached using low cost solar cells. It is achieved first in areas with abundant sun and high costs for electricity such as in California and Japan.^[3] Grid parity has been reached in Hawaii and other islands that otherwise use diesel fuel to produce electricity. George W. Bush has set 2015 as the date for grid parity in the USA.^[4][5] General Electric's Chief Engineer predicts grid parity without subsidies in sunny parts of the United States by around 2015.

Other companies predict an earlier date.^[6]Oerlikon Solar has said its facilities will achieve grid parity by 2010 in connection with the opening of the company’s new fully-automated thin-film pilot line at the Solar Valley in Trübbach, Switzerland ^[7].

Grid parity was delayed by the higher than expected cost of solar-grade silicon. Manufacturing capacity dropped after the collapse of the dotcom bubble in 2001, while the subsidies associated with feed-in tariffs in Germany introduced in 2004 increased the costs of solar cells worldwide and diverted suitable silicon away from sunnier and therefore more potentially economic locations such as India and Africa.^[8][9]

A number of analysts have predicted that polysilicon prices will drop as companies build additional polysilicon capacity more quickly than the industry’s projected demand.^[1] The development of the Renewable Energy Corporation´s Singapore site will enable REC’s ability to deliver polysilicon solar products that can compete with traditional energy sources in the sunny areas of the world without government incentives.^[10]

On the other hand, the cost of producing upgraded metallurgical-grade silicon, also known as UMG Si, can potentially be one-sixth that of making polysilicon.^[1]

A cadmium telluride solar cell is a solar cell based on a cadmium telluride (CdTe) thin film, a semiconductor layer to absorb and convert sunlight into electricity

Dye-sensitized solar cell is another low cost solar cell option.

This cell is promising because it is made of low-cost materials and does not need elaborate apparatus to manufacture, so it can be made in a DIY fashion and allows more players to produce it than any other type of solar cell. In bulk it should be significantly less expensive than older solid-state cell designs. It can be engineered into flexible sheets. Although its conversion efficiency is less than the best thin film cells, its price/performance ratio should be high enough to allow them to compete with fossil fuel electrical generation.

Organic solar cells is a relatively novel technology, promising substantial price reduction (over thin-film silicon) and better energy payback time. These cells can be processed from solution, enabling the possibility for a simple roll-to-roll printing process, leading to a cheap, large scale (square kilometers per month) production.

Researchers at the Massachusetts Institute of Technology (MIT) have found a way to convert windows into devices that concentrate sunlight for conversion into electricity. MIT developed a mixture of dyes that can be painted onto a pane of glass or plastic. The dyes absorb sunlight and then re-emit it within the glass in a different wavelength of light, which then tends to reflect off the interior surfaces of the glass. As the light reflects within the glass pane, it tends to get channeled along the length of the glass to its edges, where it is emitted. The MIT researchers estimate that sunlight is concentrated by a factor of 40, allowing solar cells that are optimized for such concentrated sunlight to be mounted along the edges of the window. The unique optics of the approach yields a cheap solar concentrator that does not need to be pointed toward the sun, as is needed for lens-based concentrators. MIT estimates that the process will be commercialized by Covalent Solar within the next 3 years .^[11]

Compared to conventional flat panel solar cells, CPV is advantageous because the solar collector is less expensive than an equivalent area of solar cells. CPV system hardware is typically priced around 3 USD/Watt, whereas silicon flat panels are commonly 5 USD/Watt (not including any associated power systems or installation charges). Semiconductor properties allow solar cells to operate more efficiently in concentrated light, as long as the cell junction temperature is kept cool by a suitable heat sinks. CPV operates most effectively in sunny weather, since clouds and overcast conditions create diffuse light which essentially can not be concentrated.

The technology of solar arrays of nanoantennas is expected to be highly efficient with regard to capturing energy (80% efficiency) and in the process of creating the device (cents per yard). ^[12] Small square spirals of metal can be printed on plastic sheets, using roll-to-roll machinery ^[13]. The antennas can capture energy associated with infrared radiation, which reaches the earth from the sun during the day and is emitted by the earth at night.

Commercial solar panels usually transform less that 20 percent of the usable energy that strikes them into electricity. Individual nanoantennas can absorb close to 80 percent of the available energy ^[14]. The circuits themselves can be made of a number of different conducting metals, and the nanoantennas can be printed on thin, flexible materials like polyethylene, a plastic that's commonly used in bags and plastic wrap ^[15].

Double-sided panels could absorb a broad spectrum of energy from the sun during the day, while the other side might be designed to take in the narrow frequency of energy produced from the earth's radiated heat ^[16].

• Capacitor
• Indoor light
• Investment in renewable energy
• Printed electronics
• Rectifier
• Roll-to-roll processing
• Solar hot carbon

• Photovoltaic technologies beyond conventional silicon (IDTechEx).
• Charting a Path to Low-Cost Solar.
• Business leaders: Make renewable energy cheaper (International Herald Tribune).
• The Thin Film Revolution.