Category Thin Film Solar Cells Fabrication, Characterization and Applications

Figure P.3 a) Schematic of a epitaxial cell on a highly doped low

Amorphous and microcrystalline silicon thin film solar cells

Because a-Si:H can be doped efficiently p – and n-type, the cell structure is based on a ho­mojunction. As a result of the short carrier lifetime and the low carrier mobility collection by pure diffusion of excess carriers is not very effective. Therefore a-Si:H solar cells also

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include a drift zone to improve the carrier collection. As a result the structure of the solar cell device is a p-i-n-structure where an intrinsic a-Si:H layer is sandwiched between a thin n+ and p+-type layer. Because of the low doping in the intrinsic part, the electrical field will extend all over the intrinsic layer...

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Crystalline silicon thin film solar cells

There are a large variety of crystalline Si thin film approaches. The one that is closest to the classical crystalline Si solar cell structure is the ‘epitaxial solar cell approach’. The basic idea behind this thin film approach, is the realization of a thin crystalline Si film of high electronic quality on a low cost Si carrier substrate by means of epitaxial growth as shown in Figure P.3a. The depicted structure strongly resembles the structure of a classical, self supporting bulk crystalline Si solar cell and, as a result, the basic solar cell process to produce the solar cell is very similar to the practices used within the photovoltaics (PV) industry nowadays...

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Thin film absorber materials

Conventionally, photovoltaic materials use inorganic semiconductors. The semiconductors of interest allow the formation of charge-carrier separating junctions. The junction can be either a homojunction (like in Si) or a heterojunction with other materials to collect the excess carriers when exposed to light. In principle, a large number of semiconductor materials are eligible, but only a few of them are of sufficient interest. Ideally, the absorber material of an efficient terrestrial solar cell should be a semiconductor with a bandgap of 1-1.5 eV with a high solar optical absorption (104 – 105 cm-1) in the wavelength region of 350-1000 nm, a high quantum yield for the excited carriers, a long diffusion length low recombination velocity...

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P.2 THIN FILM MATERIALS FOR SOLAR CELLS P.2.1 Thin film: definition

The reader might remark at this point that the term ‘thin film solar cell technology’ has not yet been defined in the context of this book. The definition given by Chopra et al. [5] provides a good starting point and also yields a criterion to discriminate the term ‘thin film’ from ‘thick film’. They define a thin film as a material ‘created ab initio by the random nucleation and growth processes of individually condensing/reacting atomic/ionic/molecular species on a substrate. The structural, chemical, metallurgical and physical properties of such a material are strongly dependent on a large number of deposition parameters and may also be thickness dependent...

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Preface

P.1 STATUS OF PHOTOVOLTAICS AND THE ROLE OF THIN FILM SOLAR CELLS

The large scale production of solar cells during the year 2004 surpassed the symbolic threshold of 1 GWp [1] and the total cumulative worldwide PV capacity installed is above 3 GW. Photovoltaic applications range from large scale stand alone/grid connected power stations to low power electronics.

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The photovoltaic (PV) sector has been growing with a compounded annual growth rate of nearly 30 % over the last five years and in 2004 the growth rate even amounted to a breath-taking 60 % as can be seen in Figure P.1.

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film solar cell technologies and consists of 4 % based on thin film amorphous Si solar cells and 2 % on polycrystalline compound solar cells based on CdTe and CuInSe2 (Figure P. 2).

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20%

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1999 ...

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Series Preface

WILEY SERIES IN MATERIALS FOR ELECTRONIC AND OPTOELECTRONIC APPLICATIONS

This book series is devoted to the rapidly developing class of materials used for electronic and optoelectronic applications. It is designed to provide much needed information on the fundamental scientific principles of these materials, together with how these are employed in technological applications. The books are aimed at postgraduate students, researchers and technologists, engaged in research, development and the study of materials in electronics and photonics, and industrial scientists developing new materials, devices and circuits for the electronic, optoelectronic and communications industries.

The development of new electronic and optoelectronic materials depends not only on ma­terials engineering at a pract...

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Thin Film Solar Cells Fabrication, Characterization and Applications

The unexpected death of Vladimir Arkhipov on December 10, 2005 was a sad loss for the scientific community and even more so for his young family. Shortly after returning from a conference in Boston, he went to Moscow to visit his mother and while in his hometown he suffered a heart attack. Strangely enough this happened when there was good reason to expect that he could finally settle down in Leuven. However, his destiny was to go back to his Russian roots. His family, friends and colleagues can only mourn the loss of a great personality and a great scientist.

Vladimir Arkhipov was born on January 18, 1952. He studied physics at the Moscow In­stitute of Physics and Engineering...

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