Light Trapping Properties of Solar Cells

Light Trapping Properties of Solar Cells Abstract In this paper, we have investigated the light trapping properties of solar cells based on one-dimensional photonic crystal (1DPC) by using finite difference time domain (FDTD) method. Light trapping is essential for thin film solar cells due to the limited absorption in long wavelength range. Here, we used different types of solar cell structures and to explore their photonic ray theories (electric field propagation) and numerical simulations. The one-dimensional thin film solar cell consists of distributed Bragg’s reflector (DBR), Metal back reflector, grating and anti-reflection coating (ARC). The influence of the grating period and depth, the optimal path length has to be increased. These numerical simulations indicate that this combined photonic structure is capable of improving the external quantum efficiency and their absorption. As well as the relative enhancement increased up-to 60% for thin film silicon solar cells. We further to investigate high efficiency of thin fi lm solar cell using different structure. Index terms: Finite difference time domain (FDTD), distributed Bragg’s reflector (DBR), the grating, metal reflector, anti-reflection coating (ARC) and relative enhancement factor. Introduction The scientific community is intensively working to achieve high efficiency thin film solar cells based on silicon. Among the various energy sources, solar energy is well considered to be very promising and achieved wide applications for space and global power generation. The silicon based thin films are cheaper and easy fabrication due to well developed silicon technology. The Silicon based thin films have been the choice as active materials for solar cells, such as crystalline silicon (c-Si), amorphous silicon (a-Si), micro crystalline silicon (ÃŽ ¼c-Si) and so on [1]. The efficiency of silicon thin film solar cell (TFSC) is low due to their weak absorption in longer wavelength range. Thus the light trapping mechanism for thin film silicon solar cell becomes a vital role to improve the conversion efficiency. The crystalline silicon solar cells integrated with the DBR, metal reflector, ARC and grating. Therefore, the incident light is expected to be partially absorbed in the active l ayer of crystalline silicon (c-Si), after the support through the front anti-reflection coating layer (Si3N4) and the back reflector of aluminum (Al) or dielectric (DBR) layers. We are realized that incident light is scattered into the DBR due to the periodic grating and reflected back at the bottom interface. Therefore the way of light trapping in this design is different from usual reflectors based on metals or photonic crystals [2, 3]. In this paper, we will focus on strongly corrugated photonic crystal absorbers made up of a-Si and SiO2 layers are periodically patterned. Finally, the optical presentation of the structure will be indicated by their integrated absorption, the absorbed spectral range between 300-1200nm. This paper deals with the modeling and designing of solar cells using FDTD method. Figure 1 The schematic diagram of the solar cell structure Designing Approach Finite difference time domain (FDTD) method as a sophisticated computational method used to model advanced devices. Figure 1 shows a schematic diagram of solar cell composed of anti-reflection coating (ARC), diffraction grating and photonic crystals also known as distributed Bragg’s reflector. The distributed Bragg’s reflector (DBR) consists of alternate layers of amorphous Si (a-Si) and silicon-di-oxide (SiO2) with their refractive index 3.6 and 1.45 and thickness 56nm, 138nm respectively. The thickness of the each layer is determined by the quarter wave principle (t = ÃŽ »C /4n), where, n-is the refractive index and ÃŽ »C is the center wavelength of photonic band gap. On top of the DBR, diffraction grating is embedded which is made of a-Si and SiO2, with duty cycle (Gdc=0.5ÃŽ ¼m), period (Gp=0.6ÃŽ ¼m) and thickness (Tg=0.1ÃŽ ¼m).The anti-reflection coating (ARC) layer is made of silicon nitrate (Si3N4) and their thickness 0.07ÃŽ ¼m. Result and Discussion The wave propagation designed solar cell is shown in figure 2. We have used commercial available Full WAVE tool supplied by RSoft. We can see light interaction into the device, when one light is made incident on the solar cell. The shorter wavelength is absorbed by the active region while longer wavelength moves toward bottom layer. The grating interaction gives scattering and diffraction of light where as DBR reflects remaining light. This mechanism finally force the light waves into active region. We have designed and analyzed four different structures of solar cells to understand the light trapping mechanism. Figure 2 Schematic diagrams of solar cell structure and their electric field distribution Figure 3 (a) show absorption of solar cells in accordance to wavelength from 300 to 1200nm. To compare the performance of designed devices we have designed a planer solar cell which mainly consists of anti-reflection coating of silicon nitride. The solar cell absorption of DBR and ARC based solar cell is found to be improved than reference solar cell. However, DBR, ARC and GRA based solar cells show distinct absorption as comparisons to cell C1 and C3. We can see added absorption peak in the red and infrared part of solar spectrum for the case of cell 2. Figure 3 Absorption (a) and Quantum efficiency (b) of designed four solar cells Figure 3b shows Quantum efficiency of different types of thin film Silicon solar cells. The solar cell (C2) composed of DBR, ARC and GR Solar cell C2 shows enhanced quantum efficiency then solar cells C1 and C3. The solar cell C2 peaks between 600 and 1160nm range, which indicates the efficient trapping of light. However, reference cell has the less quantum efficiency show sharp as compare to cells C1 and C3. The overall quantum efficiency is found to be increased between the 700 to 1160nm wavelength range. The quantum efficiency clearly exposes the light absorption enhancement of the light trapping structure in certain wavelength range only. The different solar cell structure shows the highest performances and their relative efficiency was achieved up to 60%, it is compared to the reference cell. Figure 4 J-V characteristics for solar cells with different back structures The figure 4 shows the short circuit current versus voltage characteristics of four designed solar cells. The highest short circuit current can be absorbed for cell C2, C3 and C1 respectively. The short circuit current enhancement factors are 21mA/cm2, 53.8mA/cm2 and 60.5mA/cm2. The overall short circuit current of DBR with grating structure got more enhancements (~60%). Table-I shows the short circuit current, open circuit Voltage, relative enhancement factor and cell efficiency of different solar cell structures. Table-1 The comparison of optical characteristics of C-Si solar cell with different back structures with reference structure All the back structures are improved the cell efficiencies as shown in table I. The open circuit voltage (VOC= 0.7V) and the fill factor (FF=84.5%) are similar to all the structures. The back reflectors showing significant enhancement as evidenced by figure 3. Figure 5 The efficiency enhancement of c-Si solar cells with different structures The characteristic of different back reflector with active region and their enhanced efficiency as shown in figure 5. The combination of periodic grating and DBR structure indicates 60% enhancement, while aluminum with grating structure indicates 53.4% enhancement, it is compared to bare silicon or without any reflector on the back surface. It is simulated as a compare to the perfect periodic cell structure. Conclusion In conclusion, we proposed new photonic light trapping structure and the numerical simulations indicate that this combined photonic structure is capable of improving the cell efficiency by more than 55% for thin film silicon solar cell structure. We investigated the mechanism for an efficient light trapping structure for thin film solar cells using FDTD method. At wavelength range between 400 to 1200nm, we got stronger absorption peaks for silicon with metal and grating. The efficiency also increased, it is much more considerable. These results are providing a path to achieve low cost and strong efficiency enhancement for thin film silicon solar cell. Integrated of self assembled alumina and DBR for more light trapping in silicon photo voltaic (PV) devices. The high efficiency solar cell will be greatly more evident for smaller cell thickness and improved their absorption. Further, we will get more cell efficiency using metal nano sphere and texture the grating structure. Reference [1] L.Zhao, Y.H.Zuo, C.L.Zhou, H.L.Li, H.W. Diao and W.J.Wang, A highly efficient light trapping structure for thin film silicon solar cells, Solar energy 84 (2010) 110-115. [2] Krc. J, Zeman, M, Luxembourg, SL Topic, M.Modulated photonic-crystal structures as broad band back reflectors in thin-film solar cells.Applied Physics Letters, (2009), 94(15), 153501-153501-3. [3] Lord RayleighSec. R. S. On the maintenance of vibrations by forces of double frequency, and on the propagation of waves through a medium endowed with a periodic structure, Vol. 24, issue 147, (1887), 145-159. [4] A. Taflove, S.C. Hagness, Computational Electrodynamics, 2nd ed., Artech House, Norwood, MA, 2000. [5] A.F. Oskooi, D.Roundy, M. Ibanescu, P.Bermel, J. D. Joannpoulos, S.G. Johnson, Computer Physics Communications 181 (2010) 687. [6] Xing sheng, steven G. Johnson, Lirong Z. Broderick, Jurgen Michel and Lionel C. Kimerling, Integrated photonic structures for light trapping in thin film Si solar cells, Applied Physics Letters 100 (2012), 111110. [7] L.Zeng, Y.Yi, C.Hong, J.Liu, N.Feng, X.Duan and L.C. Kimerling, Efficiency enhancement in Si solar cells by textured photonic crystal back reflector, Applied Physics Letters 89 (2006), 111111.

Hinduism Essay -- Religion Spirituality Carvaka Yoga Essays

Hinduism In India there are six orthodox schools of philosophy which recognize the authority of the Vedas as divine revelation, and they generally function as pairs - Nyaya and Vaishesika, Mimamsa and Vedanta, and Samkhya and Yoga. Those who did not recognize this authority were the Jains, Buddhists, and materialists. Even in India where spiritual ideas dominate the culture there were some who were skeptical of those ideals and held to a materialist view of the world; they were called Carvaka, and their doctrine that this world is all that exists is called Lokayata. The materialists did not believe in an afterlife and found sense perception to be the only source of knowledge, denying the validity of inference or general concepts. They focused on the senses and the four traditional elements of earth, water, fire, and air. Consciousness for the Carvaka is only a modification of these elements in the body. The soul is also identified with the body, and pleasure and pain are the central experiences of life, nature being indifferent to good and evil with virtue and vice being merely social conventions. This worldly philosophy naturally ignored the goal of liberation (moksha) or simply believed that death as the end of life and consciousness was a liberation. However, they also tended to neglect the value of virtue or justice (dharma), placing all of their attention on the worldly aims of pleasure (kama) and wealth or power (artha). Although Carvaka ideas are mentioned in some ancient writings, their own ancient writings were lost, and much of what we know of the early materialists is based on criticisms of other schools. However, a famous, ancient drama called The Rise of the Moon of Intellect (Prabodha-candrodaya) reveals some of the beliefs of this worldly movement. In this play Passion is personified and speaks to a materialist and one of his pupils. Passion laughs at ignorant fools, who imagine that spirit is different from the body and reaps a reward in a future existence. This is like expecting trees to grow in air and produce fruit. Has anyone seen the soul separate from the body? Does not life come from the configuration of the body? Those who believe otherwise deceive themselves and others. Their ancient teacher Brihaspati affirmed the importance of the senses, maintaining that sustenance and love are the objects of human life. For the materiali... ...ch developed into the Vaishnavite faith in medieval Hinduism. The poem begins with Dhritarashtra asking Sanjaya what is happening not only on the field of Kuru but also on the field of dharma (virtue, duty). Sanjaya describes how both armies are arrayed against each other blowing their conch horns to show their readiness to fight. Then Arjuna asked Krishna to position his chariot between the two armies, and there he saw many of his relatives on the other side, causing him to feel faint and consider not fighting. Even though the others are killing, Arjuna does not think it would be worth it to do so, even for sovereignty of the three worlds, let alone an earthly kingdom. Evil would come to him, he says, if he should kill his relatives. How could this bring happiness? This family destruction is wrong and would destroy ancient family duties and bring on lawlessness, which would lead to corruption of the women and caste mixing. Why should he kill for greed of royal pleasures? It would be greater happiness for him to be killed unresisting and unarmed. Thus Arjuna's mind was overcome by sorrow. Krishna, who is called the Lord, responds by upbraiding Arjuna for timidity and cowardice

Emerging Markets: Brazil Case Study Essay

I. Summary Brazil’s agricultural advantage stems from its extensive natural resources. The country’s competitors either utilize more supplies or more time in order to yield an amount that can rival Brazil’s production. Although every other country desires the agricultural production capable of Brazil, Brazil‘s government is determined to invest in industrialization in order to modernize its economy. While Brazil has a large amount of natural resources available for use, its government must provide the funding of the growing industrialization, to include: energy, materials, and increased employee earnings. II. Problem Brazil’s success in agriculture is attributed to vast lands, diverse climates, and a large population pool for labor (Brazil Agribusiness Report – Q4 2013, 2013). Without regard to its solid base in agriculture, the Brazilian government is attempting to modernize the economy through industrialization. Alongside this movement comes the â€Å"Brazil† cost: the increased operating cost of energy, raw materials, and wages. Also, in addition to paying more to industrialize, the government compensates domestic, uncompetitive industries enabling the theory of protectionism. III. Effective Solutions/Strategies In response to Brazilian President Dilma Rousseff’s desires to become a world-class manufacturing base, the country can reassess its comparative advantage in agriculture and redirect resources solely to those businesses. According to Brazil Agribusiness Report – Q4 2013, its agricultural production is yielding lower than expected numbers with respect to international standards and, therefore, still has potential for growth. Alternatively, Brazil can strategize by addressing agricultural weaknesses via industrialization. First, seize the opportunity to grow and re-attack infrastructure to promote expansion and competition. Then, allow for raised incomes, as they will decrease farmers’ debts and allow for reinvestment in the economy. Finally, although the â€Å"Brazil cost† will hurt in the short-term, a higher-paid population will result in a hygienic environment  producing greater quality of products. Therefore, previously instated non-tariff barriers due to health concerns will decrease allowing for a greater degree of expansion. IV. Questions for Discussion Why is Brazil’s agriculture so competitive? Why do its manufacturing industries lack competitiveness? Brazil’s agriculture is competitive because its environment contains natural and inexpensive resources that other nations would have to spend extra time and money to produce or acquire. Furthermore, Brazil gained a distinctive comparative advantage in agriculture and livestock by doing away with nontariff barriers and reducing import tariffs on similar products other countries were trying to bring into the country (Brazil: Economic background, 2006). With regard to underdeveloped manufacturing industries, Brazil lacks competitiveness for the same reason its agricultural competitors fall short. The â€Å"Brazil cost† of energy, raw materials, and wages is exponential compared to another nation primed to capitalize on manufacturing. As a result, domestic industrial products are costly compared to international competitors so consumers will frequent the competitor. Why have Brazil’s governments in both the 20th and 21st century been eager to develop world-class manufacturing? According to the closing case, the Brazilian government seeks to modernize its economy through world-class manufacturing. I would argue that the core reason is to achieve globalization through a combination of manufacturing and agriculture. Employing globalization means greater economic growth and standards of living, as well as attracting numerous low-end manufacturing jobs. Therefore, by modernizing its economy, Brazil fortifies its potential as a developed economy, which could launch it onto the global platform for competition in industry. How can Brazil shift some of its resources from uncompetitive industries to competitive industries? Via resource mobility, Brazil can shift resources used in uncompetitive industries to competitive industries in order to bolster the competitive industries’ potential. Furthermore, the government can shift strategic intervention and subsidies from uncompetitive industries to competitive industries. ON ETHICS: While President Rousseff’s critics accuse her of ignoring Brazil’s lack of comparative advantage in manufacturing, her supporters argue that her policies force Brazil to reduce its dependence on  foreign-made manufacturing goods. If you were to participate in this debate, which side would you be on? I would be on the side of her supporters. Through research, I have found that Brazil has extraordinary potential to grow its agricultural sectors through industrialization. By reducing manufacturing imports and producing and employing its own industrial products, Brazil not only increases domestic income and the standard of living, but also solidifies the nation’s comparative advantage in agriculture. Although, I will say that finding the balance between directing resources towards industry versus agriculture will be a delicate quest. References Brazil: Economic background. (2006). (). New York: The Economist Intelligence Unit. Retrieved from http://search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/466598073?accountid=27203 Brazil Agribusiness Report – Q4 2013. (2013). (). London: Business Monitor International. Retrieved from http://search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/1436333107?accountid=27203

Roman Republic History and Facts Essays

Roman Republic History and Facts Essays Roman Republic History and Facts Essay Roman Republic History and Facts Essay Essay Topic: The Republic Rome According to legend, the city of Rome was founded by two twin brothers Romulus and Remus. They were kidnapped when they were still babies and left near the Tiber River. The wolves cared for them but when they grew up, they found a shepherd and the shepherd also cared for them. They founded the city of Rome but they quarreled with the leader of it but some historians say that the name of the city has been theirs. Romulus won and named him the city of Rome. History of Rome Rome was governed by kings, but after only seven of them had ruled, the Romans took power over their own city and ruled themselves. They then instead had a council known as the senate which ruled over them. From this point on one speaks of the Roman Republic. The word Republic itself comes from the Latin (the language of the Romans) words res publica which mean public matters or matters of state. The senate under the kings had only been there to advise the king. Now the Senate appointed a consul, who ruled Rome like a king, but only for one year. This was a wise idea, as like that, the consul ruled carefully and not as a tyrant, for he knew that otherwise he could be punished by the next consul, once his year was up. | Rome knew four classes of people. This division was very important to the Romans. The lowest class were the slaves. They were owned by other people. They had no rights at all. The next class were the plebeians. They were free people. But they had little say at all. The second highest class were the equestrians (sometimes they are called the knights). Their name means the riders, as they were given a horse to ride if they were called to fight for Rome. To be an equestrian you had to be rich. The highest class were the nobles of Rome. They were called patricians. All the real power in Rome lay with them. The Roman Republic was a very successful government. It lasted from 510 BC until 23 BC almost 500 years. In comparison the United States of America, it only exists since 1776 less than 250 years. Ancient Roman Gods 12 Greek Olympians| 12 Roman Olympians| Hera Queen of heaven (Zeuss wife) and goddess of marriage| Juno goddess of Marriage| Zeus King of gods/heaven| Jupiter A. K. A Jove The King of the gods and the god of the sky| Hades god of underworld| Pluto – god of the dead| Poseidon god of sea| Neptune god of the Sea| Hestia goddess of hearth/domesticity| Vesta goddess of the Hearth, the Home and the Roman state| Ares god of war| Mars god of War| Hephaestus Blacksmith of gods| Vulcan god of Fire, the Forge and Blacksmiths| Apollo god of music| Apollo god of the sun, music, medicine and healing, archery and prophecy| Hermes Patron of thieves and merchants/traders, messenger of Zeus| Mercury Messenger of the gods and Finance. goddess of moon| Diana goddess of Hunting| Aphrodite goddess of love and beauty| Venus goddess of Love and Beauty| Athena goddess of wisdom, justice, crafts, and war| Minerva goddess of Wisdom|

How I Quit

How I Quit Whether looking for a job to pay the bills or taking the next step on your career, the search can feel like an endless day and night grind. We’ve all been there – written numerous cover letters, tweaked words on resumes, and gone to networking events where we know no one. The old adage is true, â€Å"it’s a full time job finding a full time job.† But, it is also important to remember that part of the process should be fun. You should be focusing on learning about yourself, what you want to spend your 10,000 hours on, and how you can learn from your failings to make yourself a more attractive job seeker to employers. On top of all of that, sometimes it is just good to draw inspiration from other people’s successes and failures. After hours of job hunting, take a moment and enjoy these inspirational career tidbits.Jimmy Fallon reads #HowIQuitWhile you might be looking for your next job, it is important to remember that not all jobs are dream jobs. And sometimes, even dream jobs turn out to be nightmares. Many jobs run their course, so Fallon highlights some quirky #HowIQuit stories.This is Off CampusThe Off Campus Podcast is relatively unknown in the burgeoning podcast world, but it is certainly drawing attention of late. Each episode is an interview with someone honing in on their experiences in pursuing their dream, what worked, and what did not. [Embed] https://soundcloud.com/this-is-off-campus/malik-yoba-adviceFor more, visit http://thisisoffcampus.org/interviews.Marina Shifrin’s Interpretive DanceRemember when I wrote that sometimes dream jobs turn out to be nightmares. It seems like this was the case for the now viral-famous Marina Shifrin, whose catchy video has nearly 20 million views on YouTube! Here is the video and then a little more about the sudden fame Shifrin received.What happened after she quit? Visit huffingtonpost.com/shira-lazar/i-quit-kanye-west-dancing_b_4067344.htmlIt could be worsePossibly one of t he best things about finding a job is that you do not have to look for another one every waking hour anymore! On the other hand, you could be Homer Simpson, who has had (in this video) 101 jobs.Got a story on how you quit? Share it using #PursueYourDreamTJN

Analysing a newspaper Essay Example | Topics and Well Written Essays - 2500 words

Analysing a newspaper - Essay Example The society was structured in a manner that male dominated over women. Most leaders were male chauvinists hence male supremacy reigned. The legal system did not incorporate ways of dealing with domestic violence. Most women who suffered violence ended up being victimized as part of the problem. The article on The Guardian website gives a review on how domestic violence issue has been handled in the UK. The news value is educative and concern peaceful co-existence in a family or domestic set-up. The news is also bad as it highlights violence in homes. Violence affects relationships and consequently leads to health and psychological problems. The news angle is neutral but rebukes perpetrators of violence. It does not support violence in heterosexual or homosexual relationships. The article has employed a criticism language on the government for laxity in coming up with an appropriate legislation in time. The editorial agenda is to sensitize readers on the need to stop domestic violence in families (Humphreys et al. 2013). The article gives insight on how the fight against domestic violence has come a long way. With no legislations relating to domestic violence, most men took advantage of the situation. However, with the emergence of civil and human rights movements, the vice came to shame. Most citizens became sensitized on the need for peace in the family. Couples had to find better ways to resolve their differences. Women’s Aid was founded in 1970 as a feminist movement and campaign tool. Domestic violence and gender oppression became a priority to deal with for the group. Domestic violence and numerous forms of abuse were decisively dealt with by Women’s Aid among other groups that were founded. In 1979, statistic revealed that two women got killed weekly by their former or current partner. The articles makes cites government statistics and other two sources on domestic violence. The sources add information about the

Socrates Discourse Essay Example | Topics and Well Written Essays - 500 words

Socrates Discourse - Essay Example In that context Socrates classifies his oppressors to be as much enshrined in the machinations of the past as in the present. Socrates unravels the ploys of his detractors to attribute his fame and name to some esoteric ability to perform mysterious and unnatural feats. As per Socrates, his fame could be deemed to be the direct outcome of a wisdom that is natural and human and therefore not beyond the aspirations of any human. As per the words of Socrates, his present plight originated from his honest and bold audacity to question the validity and truthfulness of the elites of his times, be it the politicians, seers, poets, artisans or teachers. The trial of Socrates originated not from some personal sin or crime, but rather from the daring of the accused to indulge in a free play of ideas, thereby making the populace see through their proponents’ so called wisdom and sensibility. As per the Apology, the only crime Socrates seems to have committed is to challenge the status qu o of the elites of his times. In