Amorphous silicon solar cells

Gordon, R. G, Proscia, J., Ellis, F., and Delahoy, A., Texture Tin Oxide Films Produced by Atmospheric Pressure Chemical Vapor Deposition from Tetramethyltin and Their Usefulness in Producing Light Trapping in Thin Film Amorphous Silicon Solar Cells, >/or Energy Materials, (18) 263-281 (1989)... 

We have already mentioned amorphous silicon solar cells. New processes have been developed to manufacture solar cells based upon deposition of very thin films of photosensitive materials. Such processes have a distinct cost advantage since once the films are deposited, little further processing is needed to form the final solar cell module. 

Schropp and Zeman [11] have classified current production systems for amorphous silicon solar cells. They argue that cost-effective production of solar cells on a large scale requires that the product of the deposition time needed per square meter and the depreciation and maintenance costs of the system be small. Low... 

F.R. Zhu, T. Fuyuki, H. Matsunami, and J. Singh, Assessment of combined TCO/metal rare contact for thin film amorphous silicon solar cells, Sol. Energy Mater. Sol. Cells, 39 1-9, 1995. 

Lin GH, Kapur M, Kainthla RC, Bockris JOM (1989) One step method to produce hydrogen by a triple stack amorphous silicon solar cell. Apl Phys Lett 55 386-387... 

Carlson DE, Wronksi CR (1976) Amorphous silicon solar cell. Appl Phys Lett 28 671-673... 

Carlson DE (1989) Amorphous silicon solar cell. IEEE Trans Electron Devices 36 2775-2780... 

Currao A, Reddy VR, van Veen MK, Schropp REI, Calzaferri G (2004) Water splitting with silver chloride photoanode and amorphous silicon solar cell. Photochem Photobio Sci 3 1017-1025... 

The efficiency of the amorphous silicon solar cell has reached about 8%, and the cost of the electricity generated is estimated to become comparable with that by fossil fuels in near future. In spite of this situation, the production of a light-weighing... 

This condition is quite easy to fulfill for amorphous silicon solar cells, as... 

Gordon et al. [59] proposed a figure of merit defined by the ratio of the electrical conductivity over the optical absorption coefficient in the visible spectral range. They tested many dopants for AP-CVD ZnO films, and obtained the highest figure of merit for fluorine-doped ZnO, which they used as TCO for amorphous silicon solar cells. 

Furthermore, these data strongly suggest that the positive temperature dependence of Isc, FF, and r) may be characteristic for solar cells based on organic semiconductors that show a temperature-activated behavior for charge transport, resulting in higher mobility/conductivity at higher temperatures (as also observed, for example, for some types of amorphous silicon solar cells [162]). 

Commercialization of amorphous silicon solar cells started in 1980 when Sanyo introduced calculators powered only by small solar-cell panels (total area 5 cm2). Shortly thereafter, Fuji Electric also started producing a-Si H solar cells for calculators. As of 1983, a-Si H photovoltaic devices are produced for several other applications such as photodetectors, power supplies for watches, and NiCd battery chargers. Before the end of 1984 one may see a-Si H solar panels used in larger-scale applications such as irrigation and remote electrification. 

Fig. 8. Current-voltage characteristic of a p-i-n cell fabricated on a glass substrate r]= 10.1%, area = 1.09 cm2. Vx = 0.84 V, Jm — 1.78 mA cm-2, FF = 0.676, illumination = 98.62 mW cm-2, T= 25.7°C. [From Catalano et al., Attainment of 10% conversion efficiency in amorphous silicon solar cells. Conf. Rec. IEEE Photovoltaic Spec. Conf., Vol. 16, 1982 IEEE.]...

As mentioned in Section 9, the highest conversion efficiency observed to date for an amorphous silicon solar cell is 10.1 % (Catalano et al, 1982). The theoretical limit for the conversion efficiency of a single-junction a-Si H cell can be estimated to be —20%. This follows from an upper limit of — 22 mA cm-2 for JK as determined from optical absorption data (optical path length — 2 fim), and from upper limits of —1.0-1.05 V for and -0.86 for the fill factor (Tiedje, 1982). 

Fig. 3. Equivalent circuit of amorphous silicon solar cell showing voltage source, photoconductive resistance, and fixed series resistance.

H.R Maruska, T.D. Mustakas, Influence of the wavelength of incident light on shunt conductance and fill factor in amorphous silicon solar cells, IEEE Trans. Electron Devices 31 (1984) 551-558. 

The development of amorphous silicon solar cells has progressed so well in recent years that they threaten to dominate the field of solar energy conversion. It is difficult to see how wet systems can compete with these cells, the only limitations of which arise from design problems. In the near future, it seems probable that their only failure wOl be the material used to support the cells. The progress and status of this subject does not come within the scope of this review and the interested reader should consult journals directed more towards solid-state physics than photochemistry. In this Section, we consider only aspects of photovoltaics that are directly relevant to photochemistry. 

Deckman H. W., Wronski C. R., Witzke H. and Yablonovitch E. (1983), Optically enhanced amorphous silicon solar cells , Appl. Phys. Lett. 42, 968-670. 

Tabuchi et al. [241] applied boron-doped ZnO films combined with a ZnO/AgAl back reflector to amorphous silicon solar cells. They observed the following optimal characteristic values = 18.6 mAcm , = 0.893 V, efficiency 11.9%, fill factor = 0.715. 

If the band-tail states are a fundamental property of the amorphous state, as seems likely, then one inescapable consequence is that amorphous semiconductors have intrinsic nonradiative recombination centers that cannot be removed, unlike the conventional defects and impurities in crystalline semiconductors. It is well known that nonradiative recombination limits the output voltage in solar cells. It has been shown (Tiedje, 1982) that the band-tail distributions, inferred from the transport experiments described in this chapter, limit the output voltage of amorphous silicon solar cells to 1.0 V for material with an optical (Tauc) gap of 1.7 eV. For comparison, a crystalline semiconductor with the same gap limited only by radiative recombination would have a maximum output voltage of 1.4 eV. 

The fabrication of high quality doped a-Si H films is desirable for many technical applications. In particular, amorphous silicon solar cells rely on highly conductive and layers with go photovoltaic properties (Carl-... 

ASA (Advanced Semiconductor Analysis) has been developed by the group of Prof. Miro Zeman at the Technical University of Delft in the Netherlands as simulation software optimized for amorphous silicon solar cells [236]. Because of this focus on amorphous silicon, the software has several features that make it advantageous for... 

J. Krd, M. Zeman, O. Kluth, F. Smole, M. Topic, Effect of surface roughness of ZnO Al films on light scattering in hydrogenated amorphous silicon solar cells. Thin Solid Films 426 (1), 296-304 (2003)... 

D. Dtakacs, S. Lim, P. Matheu, W. Mar, E. Yu, Improved performance of amorphous silicon solar cells via scattraing from surface plasmon polaritons in nearby metallic nanoparticles. AppL Phys. Lett. 89(9), 093103 (2006)... 

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