Combined optical and electrical characterisation of minority carrier lifetime in solar cells
01 Jan 2019-
TL;DR: In this article, a novel method to quantify the localised carrier collection efficiency of thin-film solar cells is presented, by integrating a theoretical model with data from a newly developed combined measurement system capable of measuring spectrally-resolved photoluminescence (PL), time-resolution photoluminance (TRPL), and transient photocurrent decay (TPCD) at the same spot on the solar cell.
Abstract: This thesis presents a novel method to quantify the localised carrier collection efficiency of thin film solar cells by integrating a theoretical model with data from a newly developed combined measurement system capable of measuring spectrally-resolved photoluminescence (PL), time-resolved photoluminescence (TRPL) and transient photocurrent decay (TPCD) at the same spot on the solar cell. This combined measurement approach allows for the identification and further understanding of the limiting factors in the carrier collection efficiency of solar cells. [Continues.]
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01 Jan 1983
TL;DR: This book describes the fundamental aspects of fluorescence, the biochemical applications of this methodology, and the instrumentation used in fluorescence spectroscopy.
Abstract: Fluorescence methods are being used increasingly in biochemical, medical, and chemical research. This is because of the inherent sensitivity of this technique. and the favorable time scale of the phenomenon of fluorescence. 8 Fluorescence emission occurs about 10- sec (10 nsec) after light absorp tion. During this period of time a wide range of molecular processes can occur, and these can effect the spectral characteristics of the fluorescent compound. This combination of sensitivity and a favorable time scale allows fluorescence methods to be generally useful for studies of proteins and membranes and their interactions with other macromolecules. This book describes the fundamental aspects of fluorescence. and the biochemical applications of this methodology. Each chapter starts with the -theoreticalbasis of each phenomenon of fluorescence, followed by examples which illustrate the use of the phenomenon in the study of biochemical problems. The book contains numerous figures. It is felt that such graphical presentations contribute to pleasurable reading and increased understand ing. Separate chapters are devoted to fluorescence polarization, lifetimes, quenching, energy transfer, solvent effects, and excited state reactions. To enhance the usefulness of this work as a textbook, problems are included which illustrate the concepts described in each chapter. Furthermore, a separate chapter is devoted to the instrumentation used in fluorescence spectroscopy. This chapter will be especially valuable for those perform ing or contemplating fluorescence measurements. Such measurements are easily compromised by failure to consider a number of simple principles."
28,073 citations
TL;DR: The mathematical theory behind the simple random walk is introduced and how this relates to Brownian motion and diffusive processes in general and a reinforced random walk can be used to model movement where the individual changes its environment.
Abstract: Mathematical modelling of the movement of animals, micro-organisms and cells is of great relevance in the fields of biology, ecology and medicine. Movement models can take many different forms, but the most widely used are based on the extensions of simple random walk processes. In this review paper, our aim is twofold: to introduce the mathematics behind random walks in a straightforward manner and to explain how such models can be used to aid our understanding of biological processes. We introduce the mathematical theory behind the simple random walk and explain how this relates to Brownian motion and diffusive processes in general. We demonstrate how these simple models can be extended to include drift and waiting times or be used to calculate first passage times. We discuss biased random walks and show how hyperbolic models can be used to generate correlated random walks. We cover two main applications of the random walk model. Firstly, we review models and results relating to the movement, dispersal and population redistribution of animals and micro-organisms. This includes direct calculation of mean squared displacement, mean dispersal distance, tortuosity measures, as well as possible limitations of these model approaches. Secondly, oriented movement and chemotaxis models are reviewed. General hyperbolic models based on the linear transport equation are introduced and we show how a reinforced random walk can be used to model movement where the individual changes its environment. We discuss the applications of these models in the context of cell migration leading to blood vessel growth (angiogenesis). Finally, we discuss how the various random walk models and approaches are related and the connections that underpin many of the key processes involved.
1,313 citations
TL;DR: In this paper, transient photovoltage and differential charging experiments, complemented by transient absorption data, were used to determine charge carrier lifetimes and densities in a poly(3-hexylthiophene): methanofullerene solar cell at Voc as a function of white light bias intensity.
Abstract: We use transient photovoltage and differential charging experiments, complemented by transient absorption data, to determine charge carrier lifetimes and densities in a poly(3-hexylthiophene): methanofullerene solar cell at Voc as a function of white light-bias intensity. For a typical device, the charge carrier decay dynamics are observed to exhibit an approximately third order dependence on charge density (dn∕dt∝n3).
492 citations
TL;DR: In this article, the charge collection efficiency of dye-sensitized nanocrystalline TiO2 solar cells is estimated from the respective time constants for charge recombination at open circuit τoc and the combined processes of charge collection and charge recombinations at short circuit τsc obtained by IMVS and IMPS measurements.
Abstract: Intensity modulated photovoltage spectroscopy (IMVS) and intensity modulated photocurrent spectroscopy (IMPS) are used to evaluate the charge-collection efficiency of dye-sensitized nanocrystalline TiO2 solar cells. The charge-collection efficiency of the photoinjected electrons from dye sensitization is estimated from the respective time constants for charge recombination at open circuit τoc and the combined processes of charge collection and charge recombination at short circuit τsc obtained by IMVS and IMPS measurements. Three models are developed for relating the charge-collection efficiency to τoc/τsc. The first model determines the charge-collection efficiency from τoc/τsc without considering the underlying physical processes measured by IMVS and IMPS. The second model obtains τoc/τsc by simulating the frequency response of IMVS and IMPS from the time-dependent continuity equation for simplified conditions. The third model determines the time constants for IMVS and IMPS from electron-concentration p...
373 citations
TL;DR: In this article, the authors provide an overview of the current state of our scientific understanding and technological development of copper chalcogenide devices and materials, and provide a comparison between the two materials.
Abstract: Solar cells based on copper ternary chalcogenide compounds and alloys have emerged over the last 20 years as a promising solution to the problem of high-cost solar cells. Solar power conversion efficiencies exceed 21% in laboratory devices using thin films of these materials, and their characteristic thinness results in negligible direct materials costs per unit area compared with wafers. Photovoltaic devices made from these materials have also been shown to be intrinsically stable, circumventing the historical disadvantage of degradation typical of earlier thin film solar cell technologies. However, these copper chalcogenide devices and materials are relatively complex. This article provides an overview of the current state of our scientific understanding and technological development of them.
333 citations