Optical Magnetometry

Some of the most sensitive methods of measuring magnetic fields utilize interactions of resonant light with atomic vapor. Recent developments in this vibrant field are improving magnetometers in many traditional areas such as measurement of geomagnetic anomalies and magnetic fields in space, and are opening the door to new ones, including, dynamical measurements of bio-magnetic fields, detection of nuclear magnetic resonance (NMR), magnetic-resonance imaging (MRI), inertial-rotation sensing, magnetic microscopy with cold atoms, and tests of fundamental symmetries of Nature.Comment: 11 pages; 4 figures; submitted to Nature Physic

P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance

Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT:PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications

Comparative study: the effect of annealing conditions on the properties of P3HT:PCBM blends

This paper presents a detailed study on the role of various annealing treatments on organic poly(3-hexylthiophene) and [6]-phenyl-C61-butyric acid methyl ester blends under different experimental conditions. A combination of analytical tools is used to study the alteration of the phase separation, structure and photovoltaic properties of the P3HT:PCBM blend during the annealing process. Results showed that the thermal annealing yields PCBM ‘‘needle-like’’ crystals and that prolonged heat treatment leads to extensive phase separation, as demonstrated by the growth in the size and quantity of PCBM crystals. The substrate annealing method demonstrated an optimal morphology by eradicating and suppressing the formation of fullerene clusters across the film, resulting in longer P3HT fibrils with smaller diameter. Improved optical constants, PL quenching and a decrease in the P3HT optical bad-gap were demonstrated for the substrate annealed films due to the limited diffusion of the PCBM molecules. An effective strategy for determining an optimized morphology through substrate annealing treatment is therefore revealed for improved device efficiency.Web of Scienc

Modeling organic electronic materials: bridging length and time scales

Organic electronics is a popular and rapidly growing field of research. The optical, electrical and mechanical properties of organic molecules and materials can be tailored using increasingly well controlled synthetic methods. The challenge and fascination with this field of research is derived from the fact that not only the chemical identity, but also the spatial arrangement of the molecules critically affects the performance of the material. Thus synthetic, fabrication, characterisation and computational scientists need to work closely to relate a materials performance in a device to the molecular details that cause and optimise that performance. For computational scientists in particular, the need to relate macroscopic device performance to details of molecular electronic structure brings challenges in methodology due to the need to bridge many orders of time and length scales. This article provides a survey of computational methods applied to multiple-length and time scale problems in organic electronic materials. Here we seek to highlight a few particular approaches that expand the simulation toolbox

Modeling organic electronic materials: bridging length and time scales

Organic electronics is a popular and rapidly growing field of research. The optical, electrical and mechanical properties of organic molecules and materials can be tailored using increasingly well controlled synthetic methods. The challenge and fascination with this field of research is derived from the fact that not only the chemical identity, but also the spatial arrangement of the molecules critically affects the performance of the material. Thus synthetic, fabrication, characterisation and computational scientists need to work closely to relate a materials performance in a device to the molecular details that cause and optimise that performance. For computational scientists in particular, the need to relate macroscopic device performance to details of molecular electronic structure brings challenges in methodology due to the need to bridge many orders of time and length scales. This article provides a survey of computational methods applied to multiple-length and time scale problems in organic electronic materials. Here we seek to highlight a few particular approaches that expand the simulation toolbox

Molecular dynamics study of the local structure of photovoltaic polymer PCDTBT

To meet the huge demand for renewable energy, significant research effort focuses on creating efficient organic photovoltaic (OPV) devices. In comparison to silicon-based semiconductors, OPV materials have many superior properties such as cost effectiveness, being lightweight, and flexibility, which lead to a high potential for the replacement of silicon-based semiconductors. Recently, a large number of new alternating copolymer materials have demonstrated high power conversion efficiency (PCE). These successful polymers typically have low long-range order but a high hole mobility which directly affects the PCE which depends on polymer structure. In this study, a solution molecular model for poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]:[6,6]-phenyl (PCDTBT) is developed and subsequently a molecular dynamics simulation conducted in order to understand the structure of the polymer solution. The simulation results are consistent with a low-solubility polymer that requires long equilibration times to planarize. The structural addition of side chains to inhibit rotation of thiophene rings could improve the conjugation and processability of PDCTBT leading to further improvements in OPV efficiency or hole mobility

Molecular dynamics study of the local structure of photovoltaic polymer PCDTBT

To meet the huge demand for renewable energy, significant research effort focuses on creating efficient organic photovoltaic (OPV) devices. In comparison to silicon-based semiconductors, OPV materials have many superior properties such as cost effectiveness, being lightweight, and flexibility, which lead to a high potential for the replacement of silicon-based semiconductors. Recently, a large number of new alternating copolymer materials have demonstrated high power conversion efficiency (PCE). These successful polymers typically have low long-range order but a high hole mobility which directly affects the PCE which depends on polymer structure. In this study, a solution molecular model for poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]:[6,6]-phenyl (PCDTBT) is developed and subsequently a molecular dynamics simulation conducted in order to understand the structure of the polymer solution. The simulation results are consistent with a low-solubility polymer that requires long equilibration times to planarize. The structural addition of side chains to inhibit rotation of thiophene rings could improve the conjugation and processability of PDCTBT leading to further improvements in OPV efficiency or hole mobility

P3HT-based solar cells: Structural properties and photovoltaic performance

Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT:PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications