Use Of Tandem Solar Cells For Absorbing More Light


Gail Alvares talks to Niraj Lal, a scientist on the discovery of a new material in the solar cells that comes with specific light wavelengths. The sunlight absorbed by the silicon solar cells like the infrared light coming with 1-micrometer wavelength. Remember sunlight is high in energy and it needs to be captured. Nij is currently developing materials for the efficient capture of sun’s energy especially in the visible range of approximately 400-800nm. Nij’s idea is developing a tandem cell capable of capturing short wavelength light allowing infrared beams to pass through to be captivated by the silicon cell.

solarsystemTandem solar cells are crystalline silicon presenting low-cost solar cells with projected efficiencies of over 30%. The dual junction solar cell configuration consists of the c-Si bottom cell of high efficiency and a thin film cell that is made of low-cost materials. To reach the minimum efficiency it is important to reach 30% tandem efficiency ranging from 22% to 14% with a bandgap of 1.5 eV to2 eV respectively. The material needs are defined using a simple model with four terminal tandem in terms of the electronic band gap, luminescence, optical absorption and carrier transport.

So tandem solar cells are the latest entrant in the field of solar technology for powering up homes.

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Jack Kaye On Discover satellite


There are thousands of satellites in the orbit moving around the earth. There are 2,271 satellites in the orbit listed by Gobbard Space Flight Center. Russia has over 1,324 satellites in the orbit and the US has 658 to its credit. GPS runs on the information given by the satellites and it is the foundation of modern communication. Without satellites, we cannot monitor the meteorological happening and other surface conditions. Talk to Jack Kaye on the imaginary uses of the satellite. Jack is from the NASA Earth Science Division.

sateliteJack Kaye is the member of Senior Executive service. He was earlier associated with Goddard Space Flight Center, managed the Atmospheric Chemistry Modeling and Analysis Program at the NASA HQ. Jack talks about the images of the moon taken from the Discover satellite launched the year before. He says space allows you to look at earth differently. Though the picture is the backside of the moon, it is actually the front for the satellite, informs Jack.

The complexity of the Earth is drawn from the oceans, clouds, greenery, brown areas and the photograph was taken some millions of miles away from the earth. Jack says the Discover satellite has two instruments, one is the EPIC, camera for the images that captures the pictures and the other is for Earth radiation budget. The Discover satellite was launched by the NOAA, the Department of Defense and the NASA last year.

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