A new and simple treatment of miscibility gap calculations for ternary and quaternary semiconductors including strain is presented. Our treatment leads to the same result as that of previous treatments, in the case of lattice-matched layers, but provides a more realistic and rigorous description for coherently strained layers. We also discuss the differences between our treatment and previous treatments, including misfit strain caused by the substrate. Our treatment is applied in miscibility gap calculations for GaInNAs and GaInAsSb material systems. Theoretical predictions by miscibility gap calculations are compared with growth experiments and show reasonable agreement.
We attain good quality hydrogenated silicon carbon films grown by plasma-enhanced chemical vapor deposition. Similar to hydrogenated silicon, we observe a characteristic edge of crystallinity at medium hydrogen dilution ratios of the feedstock gases. In the transition regime between amorphous and nanocrystalline phase, our thin films exhibit a remarkable ratio of photocarrier mobility-lifetime product to dark conductivity of 10 5 ... 10 6 cm 3 A -1 and minimum light-induced degradation. The static index of refraction increases and the resonance energy decreases for films below the onset of crystallinity which points towards a higher compactness of the protocrystalline material. Hence, alloying of hydrogenated silicon with small amounts of carbon leads to the formation of SiC:H layers that feature an optical bandgap of 2.0 eV and simultaneously maintain the superior optoelectronic properties of protocrystalline silicon.
We numerically simulate performance data of hydrogenated amorphous silicon (a-Si:H) and copper indium gallium diselenide (CIGS) based solar cells for various illumination conditions. For ease of comparison, we model typical single junctions with the very same software. The study allows us to evaluate the cell feasibility in different hybrid electronic systems like smart cards, wrist watches, transponder systems, and mobile sensors. At an illumination intensity of 1 sun, the optical bandgap of the absorber material and the series resistances determine the spectral sensitivity of the solar cell to particular illumination spectra. For intensities of 10-2 suns and so-called D65 spectrum, which represents daylight under cloudy skies, the efficiency of a-Si:H solar cells nearly equates the CIGS cell performance although the AM 1.5 efficiency of the CIGS diode exceeds the one of our a-Si:H cell by more than a factorof two. Infrared-weighted black body radiation leads to superior performance of the CIGS type, whereas for ultraviolet-weighted illumination the a-Si:H cell shows better performance. For intensities below 10-4 suns theexternal shunt resistance dominates the current-voltage characteristics of both cell types, resulting in poor performance independent of the incident spectrum. We complete our study by simulating the solar-powered charging process of a gold capacitor, which serves us as a model for the energy storage within a hybrid electronic system. The charging behavior under various realistic illumination conditions shows particular cellcharacteristics: high open circuit voltages qualify a-Si:H solar cells for electronic systems that require increased voltages and CIGS cells are suited for applications with higher current need.
The integration of flexible solar Celts into clothing or accessories enables ubiquitous power generation for mobile electronic equipment. This contribution reports on recent progress in important areas of integrated phot6 voltaics' development, i.e. i) direct deposition of flexible solar cells on plastic foils: ii) forecast of the energy yield under realistic operating conditions; and iii) charge controller and system design. Modeling of the attainable energy yield proves the validity of the concept, and first prototypes demonstrate its feasibility.
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