Efficiency of photovoltaic cells

Efficiency of photovoltaic cells This years Nobel Prize has been awarded to an American physicist and chemist whose work paved the way to built efficient and low-cost polymer photovoltaic cells. Professor A. J. Heeger of University of California at Santa Barbara, US received the prestigious Nobel Prize for his research on polymer photovoltaic solar cells over the past two decades. In 1995 Heeger published a paper (science 270 1789), in which he proposed a new approach to fabricate photovoltaic devices, which led to the development of efficient solar cells. This enabled to fabricate renewable, sustainable, and recyclable, low cost photovoltaic devices which are used to convert light energy into electric current. This approach is enhanced and widely used in commercial applications to produce flexible organic solar cells. The increasing demand for energy has created a need for low cost and eco-friendly energy source. Solar power, which is a renewable energy source holds good for producing energy at low cost. Breakthrough Efficiency of Photovoltaic cells depends on the energy conversion and charge collection of the device, which are high in inorganic based photovoltaic device, however organic photovoltaic devices have major advantages over inorganic photovoltaic devices i.e., low-cost fabrication, mechanical flexibility and disposability. This led many researches to focus on polymer photovoltaic cells, hence several approaches have been proposed for fabricating photovoltaic cells like mono and bilayered organic solar cells by using photo induced electron transfer in composites of conducting polymers as donors(D) and Buckminsterfullerene and its derivatives as acceptors(A). However the conversion efficiency is limited by the carrier collection efficiency at the D-A interface. A major breakthrough in the field of organic photovoltaic cells is achieved by overcoming the limitation of the efficiency in the bilayer heterojunction, which is proposed by Heeger. A high interfacial area is achieved within a bu lk material by carefully controlling the morphology of the phase separation into an interpenetrating bicontinuous D-A network, which yields efficient photo induced charge separation, this obtained interfacial area is known as Bulk D-A heterojunction. Even though the bulk heterojunction is previously proposed by Hiramoto et al, [J. Appl. Phys. 72, 3781, 1992] but the fabrication of solar cells is far more difficult than that of Heeger approach. Heeger used composite film of poly (2-methoxy-5-(2-ethyl-hexyloxy)-1, 4-phenylene vinylene) (MEH-PPV) and soluble derivatives of buckminsterfullerene namely [6,6]PCBM and [5,6]PCBM to form a polymer blend. To overcome the limited solubility of C60, a series of soluble C60 derivatives are used, this concept of soluble C60 derivatives enabled to realize new device concept. The structure of bulk heterojunction consists of metal electrode contacts (Ca or Al) of different work function to optimise the efficiency of carrier collection of holes from donor phase and electrons from acceptor phase. Indium tin oxide (ITO) is used as anode and Ca or Al is used as anode which automatically extracts electrons and holes from the polymer blend. The performance of bulk heterojunction photovoltaic cells depends on the phase separation in polymer blend devices; so much of the research is concentrated on the precise control of the phase separation. The film formation has to be very fast, in order to obtain fine structures i.e., Phase separation has to be arrested earlier, which results in smaller domains than exciton diffusion length. This can be achieved [Adv. Mater. 12, 498, 2000] by spin coating on a heated substrate, so that the solvent evaporates faster. The quantum efficiency (percentage of photos hitting the photo reactive surface that will produce electron-hole pair) of up to 2.9% is achieved by Heeger, which is further enhanced by using different low molecular weight materials [Adv. Mater. 12, 1270, 2000]. Quantum efficiency can be improved up to 10% by using different materials. Evolution A wide range of research is carried out based on bulk heterojunction approach, which resulted in efficient photovoltaic cells; however organic solar cells degrade when exposed to ultraviolet light, which effects the life time of the cells. Energy conversion efficiency is also low when compared to its inorganic counterparts. Fig 1 shows the efficiency achieved by different research groups in the last decade. 7.9% efficiency is achieved by Solarmer Company, which is certified by National renewable energy laboratory (NREL). Whereas Heeger achieved a quantum efficiency of 2.9%, this indicates a rapid development in this field over a decade. Solarmer produce photovoltaic commercial products using bulk heterojunction approach. Another company named Konarka which is founded by Heeger also manufactures plastic electronics and solar cells with bulk heterojunction. Konarka offer conventional products like sensors, portable battery charging for PDA, mobiles and other small devices, microelectronics, portable power, remote power, building integrated photovoltaic. Plextronics is another company developing and selling pre-formulated inks as well as the know-how to print them, which are extensively tested for outdoor lifetime. Device using these products have high lifetimes of the order of years. However the efficiency of polymer photovoltaic cells is low when compared to the silicon based photovoltaic devices. In order to compete with other available technologies, the efficiency of polymer photovoltaic cells should be increased to 15% with a lifetime of 15-20 years [Solar energy, 2009, 1224]. Heeger made a significant contribution to polymer solar cells field by proposing the bulk Heterojunction approach, which has many potential applications in renewable energy.

Hitler’s Rise To Power: An Inevitable Offshoot of the Great Depression in Germany

The Great Depression caused by the Stock Market's collapse in 1929 affected the American economy like no other economic crisis in its history (Samuelson, n. d. ). Being the most severe depression experienced by the industrialized Western world (Nelson, n. d. ), its effects rippled to other economies, especially to that of Germany. The German economy was notably vulnerable because it was built out of foreign capital and was dependent on foreign trade (Gavin, 1996). The Depression abruptly restructured German society and thus, led people to seek any solution to end the crisis. Hitler proved to be the solution that Germany was looking for. Although his views were unpopular among the public, he took advantage of the hopelessness which the people felt during the Depression. Moreover, other factors that were already present in the 1920s sped his rise to popularity. Some of these were: long term bitterness among the people brought about by the Treaty of Versailles and the First World War; ineffective constitution; money for Hitler's campaign and propaganda; the existence of propaganda and programmes; Stormtrooper attacks on other parties and on Hitler's detractors as well as his personal atributes. After 1929, two other influential factors aided Hitler and ensured his success politically: the Great Depression and Hitler's recruitment by Hindenburg (Clare, 2006). Hitler's rise to power was successful and yet avoidable. His success was largely due from external factors which he exploited using duress, brilliance and propaganda (Clare, 2006). Indeed, if the Depression had not happened; chances are, there would have been no Hitler. References Clare, John. (2006). How Was Hitler Able To Become Chancellor in January 1933?   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Greenfield History Site.   Retrieved December 11, 2007 from    http://www.johndclare.net/Weimar7.htm Gavin, Philip. (1996). The Rise of Adolf Hitler: Great Depression Begins. History Place Site.   Ã‚  Ã‚   Retrieved December 11, 2007 from   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   http://www.historyplace.com/worldwar2/riseofhitler/begins.htm Nelson, Cary. (n. d.). About the Great Depression. Modern American Poetry Site. Retrieved   Ã‚  Ã‚  Ã‚  Ã‚   December 11, 2007 from http://www.english.uiuc.edu/maps/depression/about.htm Samuelson, Robert. (n. d.). Great Depression. The Concise Encyclopedia of Economics. Library of Economics and Liberty Site. Retrieved December 11, 2007 from   Ã‚  Ã‚   http://econlib.org/library/Enc/GreatDepression.html

Get the Scoop on Essay Topics on Evolution Before Youre Too Late

Get the Scoop on Essay Topics on Evolution Before You're Too Late Type of Essay Topics on Evolution An individual may have the psychological advantages of religion because it acts as a cohesive family. Then, he shows curiosity to secure more info about things happening in the court. Therefore it's immoral to have sexual relations with a girl who might become your daughter. Maybe I got the entire thing wrong, perhaps we can evolve too as a group. Among the most potent arguments for evolution is, naturally, DNA. The evolutionary theory is among the most frequently debated scientific theories. It isn't hard to argue for evolution. In my opinion, evolution has become the most probable theory considering what evidence was found. However, you may again turn to fossils for aid. It's predicated on the notion that better adapted organisms are somewhat more likely to reside on and produce offspring. Because of their random nature, if any 2 species share the very same ERV in the exact same location with the exact same inactivating mutations, they almost certainly share a frequent ancestor where the ERV initially occurred. Things You Won't Like About Essay Topics on Evolution and Things You Will Clearly, religion played a big part in the growth of American Literature. Like every argumentative essay it's essential that you understand your subject issue. If you're looking for a nice and intriguing subject, you've got to refer to the bit of advice on choosing the topic for your evolution essays. As you are discussing creation science, you're going to be held to a greater standard, and you need to be certain to represent Christ in excellence. It's known as the unifying area of biology, and schools teach it like a foundational tenant. To begin with, it's a scientific theory. Get familiar with the very best creation science offers, and don't use these doubtful arguments. Whenever your teacher does not provide you exemplification essay topics, you always have the option to attempt employing a number of the topics on the next list.1. The maturation of railroads in the united kingdom and US grew at a fast pace. In 1830 The Baltimore and Ohio Railroad was operating, amongst being among the oldest railroads in the usa, it was among the very first commercial lines on the planet. LTL capacity is fast becoming severe, and complete truckload carriers have already begun to turn away freight. Keeping the great relationship with the customers is important to raise the capability to create value for the two parties. What to Expect From Essay Topics on Evolution? Topics may differ from year to year. Throughout time, our media improved in lots of ways. Just take a better look at this video. The Nuiances of Essay Topics on Evolution Up to now, a vast range of species concepts are proposed, and many are even associated with several differing definitions. By exploring the definition of the term theory, it's important to stress the concept a theory in science isn't the exact same as its quotidian meaning. A minumum of one sheet of paper needs to be utilized to create a plane. Instead, it's a test of how well you've learned and understood the fabric of the course as taught. The purpose of this program is to develop an appreciation for a selection of topics in signal transduction. It's a body of knowledge. Currently it's the only reasonable theory that explains how the organic world developed. The compound eyes of night creatures are very tough to develop, especially by themselves. The Essay Topics on Evolution Cover Up Moreover, it's a commonly established view on the maturation of life. Ahmad and Sein (1997) stated that in a quick lifespan undertaking, the culture can't be changed. In addition, it developed a superior awareness of responsibility in any respect levels within the organisation. Accordingly, in guiding an organisation's activities and boosting the customer's satisfaction, quality management take into account the customer focus policy like increase effectiveness in the usage of the organisation's resources. The great advantage of this strategy is it is parallelizable with very little work. All the needed characteristics have to be designed into the products or services at the start. Anyway, it can be put on the output of the entire organization by measuring the total superior operation of the organization (Besterfield, 1998).

List of Common Blood Chemistry Tests

Your blood contains many chemicals, not just red and white blood cells.  Blood chemistry tests are among the most common diagnostic tests performed to detect and diagnose illnesses. Blood chemistry indicates hydration levels, whether or not an infection is present, and how well organ systems are functioning.  Here is a list and explanation of several blood tests. Table of Common Blood Chemistry Tests Test Name Function Value Blood Urea Nitrogen (BUN) Screens for renal disease, assesses glomerular function. Normal Range: 7-25 mg/dL Calcium (Ca) Assess parathyroid functioning and calcium metabolism. Normal Range: 8.5-10.8 mg/dL Chloride (Cl) Assess water and electrolyte balance. Normal Range: 96-109 mmol/L Cholesterol (Chol) High total Chol may indicate atherosclerosis related to coronary heart disease; indicates thyroid and liver function. Total Normal Range: Less than 200 mg/dLLow-Density Lipoprotein (LDL) Normal Range: Less than 100 mg/dLHigh-Density Lipoprotein (HDL) Normal Range: 60 mg/dL or greater Creatinine (Creat) High creatinine levels almost always are due to renal damage. Normal Range: 0.6-1.5 mg/dL Fasting Blood Sugar (FBS) Fasting blood sugar is measured to assess glucose metabolism. Normal Range: 70-110 mg/dL 2-hour post-prandial blood sugar (2-hr PPBS) Used to assess glucose metabolism. Normal Range: Less than 140 mg/dL Glucose Tolerance Test (GTT) Use to assess glucose metabolism. 30 min: 150-160 mg/dL1 hour: 160-170 mg/dL2 hour: 120 mg/dL3 hour: 70-110 mg/dL Potassium (K) Assess water and electrolyte balance. High potassium levels can cause cardiac arrhythmia, while low levels may cause cramps and muscle weakness. Normal Range: 3.5-5.3 mmol/L Sodium (Na) Used to assess salt balance and hydration levels. 135-147 mmol/L Thyroid-Stimulating Hormone (TSH) Measured to diagnose thyroid function disorders. Normal Range: 0.3-4.0 ug/L Urea Urea is a product of amino acid metabolism. It is measured to check kidney function. Normal Range: 3.5-8.8 mmol/l Other Routine Blood Tests Beside chemical tests, routine blood tests look at the cellular composition of blood. Common tests include: Complete Blood Count (CBC) The CBC is one of the most common blood tests. It is an assay of the ratio of red to white blood cells, types of white cells, and the number of platelets in blood. It can be used as an initial screening test for an infection and a general measure of health. Hematocrit A hematocrit  is a measure of how much of your blood volume consists of red blood cells. A high hematocrit level can indicate dehydration, while a. low hematocrit level may indicate anemia. An abnormal hematocrit may signal a blood disorder or bone marrow disease. Red Blood Cells Red blood cells carry oxygen from your lungs to the rest of your body. Abnormal red blood cell levels might be a sign of anemia, dehydration (too little fluid in the body), bleeding, or another disorder. White Blood Cells White blood cells fight infection, so a high white cell count may indicate infection, blood disease, or cancer. Platelets Platelets  are fragments that stick together to help  blood clot when a blood vessel is broken.  Abnormal platelet levels may signal a bleeding disorder (insufficient clotting) or a thrombotic disorder (too much clotting). Hemoglobin Hemoglobin is the iron-containing protein in red blood cells that carries oxygen to cells. Abnormal hemoglobin levels might be a sign of anemia, sickle cell, or other blood disorders. Diabetes can raise levels of hemoglobin in blood. Mean Corpuscular Volume Mean corpuscular  (MCV) is a measure of the average size of your red blood cells. Abnormal MCV may indicate  anemia or thalassemia. Blood Test Alternatives There are disadvantages to blood tests, not the least of which is patient discomfort! Scientists are developing less invasive tests for key measurements. These tests include: Saliva Tests Since saliva contains about 20 percent of the proteins found in blood, it offers potential as a useful diagnostic fluid. Saliva samples are typically analyzed using polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), mass spectrometry, and other analytical chemistry techniques. SIMBAS SIMBAS stands for Self-powered Integrated Microfluidic Blood Analysis System. It is a tiny lab on a computer chip that can yield blood test results within about 10 minutes. While SIMBAS still requires blood, only a 5  ÃŽ ¼L  droplet is required, which can be obtained from a finger prick (no needle). Microemulsion Like SIMBAS, microemulsion is blood test microchip that only requires a drop of blood in order to make an analysis. While robotic blood analysis machines can cost $10,000, a microchip only runs about $25. In addition to making blood tests easier for doctors, the ease and affordability of the chips make the tests accessible to the general public. References C. A. Burtis and E. R. Ashwood,  Tietz Textbook of Clinical Chemistry  (1994) 2nd edition. Elsevier.