52
nanotimes News in Brief
10-07/08 :: July/August 2010
Solar Cells // Breakthrough For More Efficient Thin-Film Solar Cells
R
esearch Cooperation Predicts Significant Improvement to the Efficiency of CIGS Thin-film
Solar Cells Scientists at Johannes Gutenberg Univer- sity Mainz (JGU) have made a major breakthrough in their search for more efficient thin-film solar cells.
Computer simulations designed to investigate the so-called indium/gallium puzzle have highlighted a new way of increasing the efficiency of CIGS thin- film solar cells. It has only proved possible to date to achieve an around 20% efficiency with CIGS cells although efficiency levels of 30% are theoretically possible.
The research team at Mainz University headed by Professor Dr Claudia Felser is using computer simulations to investigate the characteristics of CIGS, whose chemical formula is Cu(In,Ga)(Se,S)2
. This
research forms part of the comCIGS project funded by the Federal German Ministry for the Environment, Nature Conservation, and Nuclear Safety (BMU).
IBM Mainz and Schott AG are collaborating with the Johannes Gutenberg University Mainz, the Helm- holtz Center Berlin for Materials and Energy and Jena University in the project that is targeted at finding ways of optimizing CIGS solar cells. The researchers focused in particular on the indium/gallium puzzle that has been baffling scientists for years: Although it has been postulated on the basis of calculations that
the optimal indium:gallium ratio should be 30:70, in practice, the maximum efficiency level has been achieved with the exactly inverse ratio of 70:30.
With the support of IBM Mainz, Christian Ludwig of Professor Felser‘s team undertook new calculations with the help of a hybrid method in which he used a combination of density functional calculations and Monte Carlo simulations.
“Density functional calculations make it possible to assess the energies of local structures from the quantum mechanical point of view. The results can be used to determine temperature effects over wide length scale ranges with the help of Monte-Carlo simulations,“ Dr Thomas Gruhn, head of the theory group in Professor Felser‘s team, explains the me- thods used. Christian Ludwig is able to use a main- frame for his investigations that was recently dona- ted to Mainz University by IBM as part of a Shared University Research (SUR) science award.
With the aid of the simulations, it was discovered that the indium and gallium atoms are not distri- buted evenly in the CIGS material. There is a phase that occurs at just below normal room temperature in which the indium and gallium are completely sepa- rate. If the material is heated to above this demixing temperature, differently sized clusters of indium and gallium atoms do form. The higher the temperature,
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83