A low-cost solar cell is a thin-film photovoltaic cell that has a price competitive with traditional (fossil fuels and nuclear power) energy sources. This includes second and third generation photovoltaic cells, that is cheaper than first generation (crystalline silicon cells, also called wafer or bulk cells).

The crystalline silicon shortage^[1]has changed the photovoltaic cell economics, making thin films, which use little (1%) 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 had 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].

The price of solar panels fell steadily for 40 years, until 2004 when high subsidies in Germany drastically increased demand there, and greatly increasing the price of purified silicon (which is used in computer chips as well as solar panels). One research firm predicted that new manufacturing capacity began coming on-line in 2008 (projected to double by 2009) which was expected to lower prices by 70% in 2015. Other analysts warned that capacity may be slowed by economic issues, but that demand may fall because of lessening subsidies. Other potential bottlenecks which have been suggested are the capacity of ingot shaping and wafer slicing industries, and the number of specialists who coat the wafers with chemicals.^[8]

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.^[9]

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.

SolarBuzz reports that the lowest quoted thin-film module price stands at US$3.02 per watt-peak, with the lowest crystalline sillicon (c-Si) module at $4.24 per watt-peak ^[10].

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. The DSSC has been developped by Prof. Michael Grätzel in 1991 at the Swiss Federal Institute of Technology (EPFL) in Lausanne (CH).

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].

• Indoor light
• Investment in renewable energy
• Multijunction cell
• Nanoflake
• Printed electronics
• Roll-to-roll processing
• UMG-Si

• 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.