Modeling of photo-conversion efficiency for hydrogenated amorphous Si p-i-n structures

An analytical formalism to optimize the photoconversion efficiency η of hydrogenated amorphous silicon-based (a-Si:H) solar cells has been developed. This model allows firstly the optimization of a p⁺ -i-n sandwich in terms of carrier mobilities, thickness of the layers, doping levels, and others. Second, the geometry of grid fingers that conduct the photocurrent to the bus bars and ITO/SiO₂ layers has been optimized, and the effect of non-zero incidence angles of Sun’s light has been included as well. The optimization method has been applied to typical a-Si:H solar cells. The codes allow the optimization of amorphous Si based solar cells in a wide range of parameters and are available on the e-mail request

New formalism for self-consistent parameters optimization of highly efficient solar cells

We analyzed self-consistently photoconversion efficiency of direct-gap A³B⁵ semiconductors based solar cells and optimized their main physical characteristics. Using gallium arsenide (GaAs) as an example and new efficient optimization formalism, we demonstrated that commonly accepted light re-emission and reabsorption in solar cells in technologically produced GaAs (in particular, with solid- or liquid-phase epitaxy) are not the main factors responsible for high photoconversion efficiency. As we proved instead, the doping level of the base material and its doping type as well as Shockley-Read-Hall and surface recombination velocities are much more important factors responsible for this photoconversion. We found that the maximum photoconversion efficiency (about 27% for AM1.5 conditions) in GaAs with typical parameters of recombination centers can be reached for p-type base doped at 2∙10¹⁷ cm⁻³. The open-circuit voltage VOC formation features are analyzed. The optimization provides a significant increase in VOC and the limiting photoconversion efficiency close to 30%. The approach of this research allows to predict the expected solar cell (for both direct- and indirect-gap semiconductor) characteristics, if material parameters are known. The applied formalism allows to analyze and to optimize mass production of both tandem solar cell and one-junction SC parameters

Luminescent converter of solar light into electrical energy. Review

We review a status of the research on conversion of solar energy into electricity by using the systems that split the solar spectrum with a set of luminescent concentrators. Influence of the luminophore choice (rare-earth elements, dyes, or semiconductor quantum dots) and their characteristics as well as the luminescence quantum losses, when the light quanta travel inside the optical waveguide formed by the luminescent concentrator, were analyzed. The methods to minimize these losses, including optimal converter design, were discussed. The choice of design with stacked luminescent concentrators was demonstrated. The design of the stacked luminescent concentrators with optimized parameters of the transparent matrix and semiconductor quantum dots was investigated

Te covered Si(001): a variable surface reconstruction

At a given temperature, clean and adatom covered silicon surfaces usually exhibit well-defined reconstruction patterns. Our finite temperature ab-initio molecular dynamics calculations show that the tellurium covered Si(001) surface is an exception. Soft longitudinal modes of surface phonons due to the strongly anharmonic potential of the bridged tellurium atoms prevent the reconstruction structure from attaining any permanent, two dimensional periodic geometry. This explains why experiments attempting to find a definite model for the reconstruction have reached conflicting conclusions.Comment: 4 pages, 3 gif figure

Impact of semiconductor quantum dots bandgap on reabsorption in luminescent concentrator

We have investigated the influence of the average radius and its dispersion of the semiconductor quantum dots (QDs) used in luminescent solar concentrators (LSCs) on reabsorption. To minimize the detrimental reabsorption losses in LSCs, six semiconductors used to fabricate QDs with a wide range of their bulk band gap Eg0 have been considered, specifically: CdS (Eg0 = 2.42 eV), CdSe, (Eg0 = 1.67 eV), CdTe (Eg0 = 1.5 eV), InP (Eg0 = 1.27 eV), InAs (Eg0 = 0.355 eV), and PbSe (Eg0 = 0.27 eV). Altering and , we can determine the optimal size for minimal reabsorption. As it was shown, decreasing the semiconductor bulk band gap from 2.42 down to 1.24 eV we can get such optimum QD size that reabsorption reduces even below the combined experimental error in determination of the absorption coefficient and luminescence intensity. Further reduction of the gap Eg0, however, increases reabsorption at any values of r and Δr: for instance, for PbSe-based QDs of 1-nm radius and dispersion of 1%, reabsorption reaches 54%

Structural and electronic properties of the (111)2 x 1 surface of Ge from first principles calculations

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