Cadmium telluride systems

A number of companies are currently involved in thin-fllm photovoltaics [17], and low-cost multilayer thin-fllm amorphous silicon and CdTe (cadmium telluride) systems have already been installed in large numbers with efficiencies of the order of 10% and of about 80% output after 25 years of operation. Large-scale plants have been announced for the so-called CIS (cadmium indium selenide) and CGIS (copper gallium indium diselenide), technologies with production efficiencies in the range 12-13% and laboratory measurements up to 19.9% [18]. 

Commercially available PV systems most often include modules made from single-crystal or poly-ciystalline silicon or from thin layers of amoiphous (non-crystalline) silicon. The thin-filni modules use considerably less semiconductor material but have lower efficiencies for converting sunlight to direct-current electricity. Cells and modules made from other thin-filni PV materials such as coppcr-indiuni-diselenide and cadmium telluride are under active development and are beginning to enter the market. 

Mercury-cadmium-telluride is the principal semiconductor now being used in advanced infrared systems, both for military and other surveillance applications. Its preparation and use in infrared detectors and arrays was the subject of Volume 18 of this treatise. New generations of detectors and arrays require sophisticated epitaxial growth, which in turn requires precise phase diagram data. 

All infrared spectra were recorded with an IR-PLAN microscope (IR-PLAN is a registered trade mark of Spectra Tech, Inc.) integrated to a Perkin-Elmer Model 1800 Fourier transform infrared (FT-IR) spectrophotometer. The spectrophotometer consisted of a proprietary heated wire source operated at 1050°C, a germanium overcoated potassium bromide beamsplitter, and a narrow-band mercury-cadmium-telluride (HgCdTe) detector. The detector was dedicated to the microscope and had an active area of 250 x 250 pm. The entire optical path of the system microscope was purged with dry nitrogen. 

The cure of PMR-15 and its model compound 4,4 -methylene dianiline bi-snadimide (MDA, BNI) has been studied by simultaneous reaction monitoring and evolved gas analysis (SIRMEGA) using a FTIR with a mercury-cadmium telluride detector. The system allows the observation of the variation in IR spectra correlated to the gas evolution during the curing. The data show that the cy-clopentadiene evolution involves only minor modifications in the spectrum [39]. 

Cadmium telluride — A II—IV compound -> semiconductor frequently employed in infrared systems (active component in infrared detectors) and -> photovoltaic devices. Electrochemical - passivation has been employed to improve surface recombination behavior. 

Many other systems based on different nanoparticles have been introduced, such as copper indium disulfide (CuInS2) [263-265], copper indium diselenide (CuInSe2) [266,267], cadmium telluride (CdTe) [268], lead sulfide (PbS) [269,270], lead selenide (PdSe) [271], and mercury telluride (HgTe) [272]. Some of these systems show enhanced spectral response well into the infrared part of the solar spectrum [271,272]. In most cases the absorption of the nanocrystals was, however, quantitatively small as compared to the conjugated polymers. 

The ATR fibre system was built up by a FT-IR spectrometer Bruker Matrix F in connection with an ATR fibre probe (A.R.T. Photonics, Berlin 0 12 mm) and a MCT (mercury cadmium telluride) detector (Belov Technology, Co., Inc.). The probe was directly inserted through the ground neck of the reaction vessel and comprised two 1 m silver halide fibres (0 1 mm) connected to a conical two bounce diamond ATR element housed in a rod of hastelloy. Using this set-up it was possible to follow the reactions to be studied in real-time covering a spectral range from 600 to 2000 wavenumbers. 

The IR chemical imaging system measures chemically-specific IR spectra using a mercury cadmium telluride (HgCdTe) FRA detector which provides broad frequency response (out to 18 i.m), high sensitivity (2 X 10 cm Hz 2/Watt), and an operating temperature of 40-60 K. 

Theoretical conversion efficiencies of photovoltaic systems depend on the semiconductor materials used in the cells and on the ambient tanperatuie. The materials currently used to make photovoltaic cells can be grouped into three broad categories 1) expensive, efficient monocrystalline silicon, 2) less efficient but much lower cost polycrystalline silicon, and 3) the lowest cost and poorest performer, amorphous silicon material. Conversion efficiencies of commercial polycrystaUine silicon cells are 10 to 15 percent. Now the primary development areas are in how to use monocrystalline silicon with solar concentrators and making thin-film cells by depositing a 5- to 20-micron film of silicon onto an inexpensive substrate, because the estimated efficiency of these cells is above 20 percent. Work is ongoing with other materials, including amorphous silicon (a-Si), copper indium diselenide (CuInSe2 or CIS) and related materials, and cadmium telluride (CdTe). 

Infrared radiation from an incandescent source, such as an SiC Globar, is collimated and passed through a rapid-scanning interferometer so that each wavelength in the spectrum is modulated at a different frequency. The beam of radiation is then focused onto the first window of the light-pipe and the infrared beam emerging from the second window is refocused onto a sensitive detector (typically a liquid-nitrogen-cooled mercury cadmium telluride (MCT) photoconductive detector). A typical system is... 

The CALPHAD method has been widely developed for metallic systems, for oxide systems and semi-conductor systems as, for example, gallium arsenide, cadmium telluride and lead telluhde systems (8,10,11)... 

LW band employ germanium optics that have a peak transmission at 10 xm. The detectors used for LW radiometers are typically manufactured from mercury-cadmium-telluride and give a spectral response between 8 and 12 [xm in the far infrared. While the choice of the appropriate spectral-band radiometer depends on several factors, systems operating in the LW region are generally used for higher-accuracy measurements due to relatively low atmospheric absorption. However, SW systems are preferred when the surfaces have higher emissivity factors in the SW window. 

A Perkin-Elmer System 2000 FT-IR was fit with a TG/IR accessory and a GC/IR accessory. The TG/IR accessory used a deuterated triglycine sulfate (DTGS) detector. The spectra of the evolved gases were acquired and four scans co-added to generate each TG/IR time slice, corresponding to approximately a 3 C rise in TG program temperature. The GC/IR accessory was fit with a liquid nitrogen cooled, narrow band mercury-cadmium-telluride (MCT). GC/K. spectra were acquired, co-added and stored to disk at a rate of approximately 0.7 spectra per second. 

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