Modeling point defects and grain boundaries in CdSCdTe solar cells

Project: Research project

Project Details

Description

Modeling point defects and grain boundaries in CdSCdTe solar cells Modeling point defects and grain boundaries in CdS/CdTe solar cells Over the past two decades, it has become apparent that there is a need for renewable energy sources. The argument for renewables has increasingly focused on global warming caused by carbon dioxide emissions produced when fossil fuels are burned. One model predicts that, even if CO2 emissions were stabilized at todays levels, the global temperature and sea level would continue to rise for another 50-100 years [i]. The substantial changes in climate are certainly a good reason to look for alternative energy sources. Economic and national security factors also make it desirable to significantly reduce the U.S. dependence on fossil fuels. Although there are many kinds of renewable energy and each one will play an important role in replacing fossil fuels, one must consider the amount of energy required 50-100 years from now [ii] and whether the various technologies will be able to produce that amount of power. Solar thermal and solar photovoltaics are most viable amongst these technologies. Solar photovoltaic, the technology of interest here, in analogy to integrated circuits, has gone through many technology generations. Generation 1 of solar cells comprise crystalline Si and GaAs cells, generation 2 consists of thin film technologies, and generation 3 includes organic, multijunction and multiband solar cells. The push towards thin-film technology has been driven largely by predictions of future economic viability [iii,iv,v,vi]. Traditional single-crystal solar cells, such as Si and GaAs, demonstrate very high efficiencies (20-30%), but the production of crystalline material is expensive. The original reason thin-film materials were pursued was because they use much less material, which is directly related to the cost of production. Two of the leading thin-film materials are CdTe and CuInGaSe2, chosen because their direct bandgaps require a smaller absorption length than Si (requires less thickness for optimum performance). CdTe is a nearly ideal material for terrestrial solar cell production, as its bandgap of 1.45 eV (room temperature) yields the maximum theoretical efficiency for a solar cell, about 29%. The current record one-of-a-kind laboratory research cell was fabricated in 2012 by and has an efficiency of 18.7% [vii]. Some of the processes that have significantly raised the efficiencies of these cells include the introduction of O2 during the CdTe growth [viii], a CdCl2 treatment prior to contacting the CdTe [ix], and a back-contact process that contains Cu [x]. All of these processes are necessary to obtain research cells with efficiencies above 10%.
StatusFinished
Effective start/end date5/1/139/29/13

Funding

  • INDUSTRY: Domestic Company: $205,940.00

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