Solar Photovoltaic Technology: The Thin Film Option

Photovoltaics (PV)- the direct conversion of sunlight to electricity - was first discovered by scientists at the Bell Labs in 1954. In the late 1960's and 1970's most of the solar cell technology has been used for space applications to power satellites. The main work horse for the PV technology has been crystalline silicon (Si) solar cells. Over the past 15 years this has led to cost reductionfrom $35/kWh to about $0.30/kWh at the present time. Demonstrated reliability of 20 years or more has resulted in acceptance by several utilities. However, cost reductions in crystalline Si solar cells have been limited by the cost of wafering of ingots and the attendant loss of material. A number of Si sheet solar cells are also being investigated. In the past decade the emphasis of theresearch and development effort has been focused on thin film solar cells, which have the potential for generating power at a much lower cost of $1-2/Wp. Thin film solar cells that are presently being investigated and are generating global attention are: amorphous silicon (a-Si:H), cadmium telluride (CdTe), and copper indium diselenide (CuinSe2, or CIS). In the past few years, considerableprogress has been made by all three of these thin film solar cells. This paper reviews the current status and future potential of these exciting thin film solar cell technologies.