Category Solar Cell Materials

The Sun is the Limit

Common sense tells us that the energy source is certainly essential in delving into the limits of the extractible power, but thermodynamics teaches us that since we deal not with energy creation but energy conversion, we have to look at both the source and the sink. Our sink is the earth, whose ambient temperature is around 300 K, which we will take as the sink temperature.

How should we characterise the source? The sun emits a considerable power as electro­magnetic radiation (4 x 1023 kW) into space burning some 1015 g/s of hydrogen in nuclear reactions and converting some 5000 t/s of matter into pure energy. This radiation is, to a good approximation, thermal and described as blackbody radiation of a temperature of 5800 K (often approximated as 6000 K in the literature)...

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THERMODYNAMIC LIMITS

Thermodynamics sets the most fundamental limits to any energy-conversion process via its two fundamental laws: energy conservation and maximum entropy for closed systems.

The thermodynamic framework captures perfectly the fact that the useable energy (called work, W) that can be extracted from a body is only a fraction of its total internal energy (E).

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Fundamental Physical Limits to Photovoltaic Conversion

J. F. Guillemoles

Institut de Recherche et Developpement sur i’Energie Photovoltai’que (IRDEP), France

1.2 INTRODUCTION

Where to stop the quest for better devices? What does better mean? The conversion efficiency arises prominently in this respect.

More efficient devices, everything kept equal, would first translate into cheaper solar electricity. Are there limits to reducing the cost of PV electricity? In 2012, modules were sold 0.5-0.7 €/W and the cost of solar electricity is around 20 cts/kWh. In the longer term, development of photovoltaics (PV) has to be based on a major technological breakthrough regarding the use of processes and materials at very low cost, or/and on the engineering of devices offering far higher performance, harvesting most of the available solar energy...

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BOOK OUTLINE

The book starts with a clear exposition of the fundamental physical limits to photovoltaic con­version, by Jean-Francois Guillemoles. This covers the thermodynamic limits, the limitations of classical devices, and develops this theme for more advanced devices. The identification of device parameters used in other chapters can also be found in this chapter.

Material parameters, of course, also require a thorough understanding of characterisation tools, and the second chapter, by Daniel Bellet and Edith Bellet-Amalric, outlines the main material characterisation techniques of special interest in solar cell science...

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THE SUN

The starting point of all this discussion is the sun itself. In his book ‘Solar Electricity’ (Wiley 1994), Tomas Markvart shows the various energy losses to the solar radiation that occur when it passes through the earth’s atmosphere (Figure 1.1).

The atmosphere also affects the solar spectrum, as shown in Figure 1.2.

A concept that characterises the effect of a clear atmosphere on sunlight, is the ‘air mass’, equal to the relative length of the direct beam path through the atmosphere. The extraterrestrial spectrum, denoted by AM0 (air mass 0) is important for satellite applications of solar cells. At its zenith, the radiation from the sun corresponds to AM1, while AM1...

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Introduction

Gavin Conibeer1 and Arthur Willoughby2

1School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Australia 2Faculty of Engineering and the Environment, University of Southampton, UK

1.1 INTRODUCTION

The environmental challenges to the world are now well known and publicised, and all but a small minority of scientists accept that a reduction on dependence on fossil fuels is essential for addressing the problems of the greenhouse effect and global warming. Everyone is aware of the limited nature of fossil-fuel resources, and the increasing cost and difficulty, as well as the environmental damage, of extracting the last remnants of oil, gas and other carbonaceous products from the earth’s crust.

Photovoltaics, the conversion of sunlight into useful electrical ...

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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 practical level, but also on a clear understanding of the properties of mater...

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