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news digest ♦ Equipment and Materials


for semiconductor, solar and LED applications. Applied as a final protective layer, the Diamonex technical hard-coats offer extended life benefits to new or refurbished ESCs.


A paper published in Nature Photonics by researchers at the University of Notre Dame in Indiana, describes their investigations into the fundamental optical properties of a new class of semiconducting materials known as organic- inorganic ‹hybrid› perovskites. They conclude that the materials offer the best compromise between cost and performance for light harvesting.


These thin, wear-resistant films, made of diamond- like-carbon (DLC) and other nanocomposite materials, are adjusted to meet specific resistivity requirements of the ESC while protecting electronic layers and extending the overall life of the part. They have a broad range of chemical resistance, meet chamber process compatibility requirements, and can withstand high-temperature heated chuck applications.


The hard-coats can be applied to new or refurbished ESCs, even for ESCs originally designed without a sacrificial wear layer. The technical films are available for CVD, PVD, etch and ionimplant processes. The films feature mesa patterning for low defectivity and can be used in most high temperature processes.


US lab offers insights into new class of semiconductors


Hybrid perovskites are ‘best of both worlds’ for light harvesting


‹Perovskites› refers to the structural order these materials adopt upon drying and assembling in the solid state. In solid-state thin film solar cells, hybrid perovskites have recently shown light-to- electricity conversion efficiencies approaching 20 percent, rivaling that of commercial solar cells based on polycrystalline silicon. More importantly, these materials are easy and cheap to process using coating and or printing in contrast to solar technologies that typically require high purity materials, especially for silicon solar cells, and high- temperature processing.


However, the scientific community does not yet fully know how these unique materials interact with light on a fundamental level.


In this study, Joseph Manser under the direction of Prashant Kamat, present new insights into the excited-state properties of hybrid methylammonium lead iodide (CH3NH3PbI3) thin films through a technique known as ‹transient absorption pump-probe spectroscopy› . This approach was used to examine the events that occur trillions of a second after light absorption in the hybrid methylammonium lead iodide. They analysed both the relaxation pathway and spectral broadening in photoexcited hybrid methylammonium lead iodide and found that the excited state is primarily composed of separate and distinct electrons and holes known as free carriers.


«The fact that these separated species are present intrinsically in photoexcited hybrid methylammonium lead iodide provides a vital insight into the basic operation of perovskite solar cells,» Manser said. «Since the electron and hole are equal and opposite in charge, they often exist in a bound or unseparated form known as an ‹exciton.› Most next-generation photovoltaics based on low- temperature, solution-processable materials are unable to perform the function of separating these bound species without intimate contact with another material that can extract one of the charges.» This separation process siphons energy within


130 www.compoundsemiconductor.net Issue VI 2014


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