CO, absorption rates into diethanolamine (DEA)-promoted carbonate solutions were measured over a wide range of carbonate conversions and temperatures. Analysis of the data showed that the C0,-DEA reaction rate was controlled by the rate of formation of zwitterion intermediate for carbonate conversions below 30%, and was controlled by the rate of abstraction of proton from the zwitterion intermediate for carbonate conversions greater than 30%. Hydroxyl ion, free amine, and carbonate ion were identified to act as bases to abstract the proton from the zwitterion. The modeling of the CO, absorption rates and the effects of carbonate conversion and amine concentration on the C0,-DEA reaction kinetics were investigated.

In this paper, we present a novel design of a surface nanostructure that suppresses the reflectivity and provides forward diffraction for light trapping. The structure under study comprises periodic nanoislands fabricated using self‐assembly polystyrene spheres, which are applicable to large‐area fabrication. We also show preliminary fabrication results of the proposed structure. The periodic nanoislands reduce the reflectivity through gradient effective refractive indices and enhance light trapping through diffraction in a periodic structure. We first systematically study the antireflection and light trapping effects using a rigorous coupled‐wave analysis and then calculate the short‐circuit current density of a 2‐μm‐thick crystalline silicon with periodic nanoislands and an aluminum back reflector. The optimum short‐circuit current density with periodic nanoislands achieves 25 mA/cm2 theoretically, which shows a 76.9% enhancement compared with that of bare silicon. Moreover, the structure also provides superior photocurrent densities at large angles of incidence, compared with conventional antireflection coatings. Copyright © 2011 John Wiley & Sons, Ltd.

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Light-management is critical to thin film solar cells due to their usually limited optical absorption in the active layer. Conventional approaches involve employing separate techniques for anti-reflection and light trapping. Here, we demonstrate an embedded biomimetic nanostructure (EBN) that achieves both effects for hydrogenated amorphous silicon (a-Si:H) solar cells. The fabrication of EBNs is accomplished by patterning an index-matching silicon-nitride layer deposited on a glass substrate using polystyrene nanospheres lithography, followed by reactive ion etching. The profile of EBN is then reproduced layer by layer during the deposition of a-Si:H cells. We show that a solar cell with an optimized EBN exhibits a broadband enhanced external quantum efficiency due to both anti-reflection and light-trapping, with respect to an industrial standard cell using an Asahi U glass substrate which is mostly optimized for light trapping. Overall, the cell with an optimized EBN achieves a large short-circuit current density of 17.74 mA/cm(2), corresponding to a 37.63% enhancement over a flat control cell. The power conversion efficiency is also increased from 5.36% to 8.32%. Moreover, the light management enabled by the EBN remains efficient over a wide range of incident angles up to 60°, which is particularly desirable for real environments with diffused sun light. The novel patterning method is not restricted to a-Si:H solar cells, but is also widely applicable to other thin film materials.

Omnidirectional and broadband light harvesting is critical to photovoltaics due to the sun's movement and its wide spectral range of radiation. In this work, we demonstrate distinctive indium-tin-oxide nanowhiskers that achieve superior angular and spectral characteristics for crystalline silicon solar cells using angle-resolved reflectance spectroscopy. The solar-spectrum weighted reflectance is well below 6% for incident angles of up to 70° and for the wavelength range between 400nm and 1000nm. As a result, the nanowhisker coated solar cell exhibits broadband quantum efficiency characteristics and enhanced short-circuit currents for large angles of incidence.