History of the Automobile Essay

Starting in the late 1700’s, European engineers began tinkering with motor powered vehicles. Steam, combustion, and electrical motors had all been attempted by the mid 1800’s. By the 1900’s, it was uncertain which type of engine would power the automobile. At first, the electric car was the most popular, but at the time a battery did not exist that would allow a car to move with much speed or over a long distance. Even though some of the earlier speed records were set by electric cars, they did not stay in production past the first decade of the 20th century. The steam-driven automobile lasted into 1920’s. However, the price on steam powered engines, either to build or maintain was incomparable to the gas powered engines. Not only was the price a problem, but the risk of a boiler explosion also kept the steam engine from becoming popular. The combustion engine continually beat out the competition, and the early American automobile pioneers like Ransom E. Olds and Henry Ford built reliable combustion engines, rejecting the ideas of steam or electrical power from the start. Automotive production on a commercial scale started in France in 1890. Commercial production in the United States began at the beginning of the 1900’s and was equal to that of Europe’s. In those days, the European industry consisted of small independent firms that would turn out a few cars by means of precise engineering and handicraft methods. The American automobile plants were assembly line operations, which meant using parts made by independent suppliers and putting them together at the plant. In the early 1900’s, the United States had about 2,000 firms producing one or more cars. By 1920 the number of firms had decreased to about 100 and by 1929 to 44. In 1976 the Motor Vehicle Manufacturers Association had only 11 members. The same situation occurred in Europe and Japan. The first automobile produced for the masses in the US was the three-horsepower, curved-dash Oldsmobile; 425 of them were sold in 1901 and 5,000 in 1904–this model is still prized by collectors. The firm prospered, and it was noted by others, and, from 1904 to 1908, 241 automobile-manufacturing firms went into business in the United States. One of these was the Ford Motor Company which was organized in June 1903, and sold its first car on the following July 23. The company produced 1,700 cars during its first full year of business. Henry Ford produced the Model T to be an economical car for the average American. By 1920 Ford sold over a million cars. At the beginning of the century the automobile entered the transportation market as a toy for the rich. However, it became increasingly popular among the general population because it gave travelers the freedom to travel when they wanted to and where they wanted. As a result, in North America and Europe the automobile became cheaper and more accessible to the middle class. This was facilitated by Henry Ford who did two important things. First he priced his car to be as affordable as possible and second, he paid his workers enough to be able to purchase the cars they were manufacturing. This helped push wages and auto sales upward. The convenience of the automobile freed people from the need to live near rail lines or stations; they could choose locations almost anywhere in an urban area, as long as roads were available to connect them to other places. Many states in the US established motor fuel taxes that were used only to build and maintain highways helping the auto highway system become self-supporting. Popularity of the automobile has consistently moved with the state of the economy, growing during the boom period after World War I and dropping abruptly during the Great Depression, when unemployment was high. World War II saw a large increase in mass transit because employment was high and automobiles were scarce. The rapid growth of car owners after World War II, particularly in the United States and Western Europe demonstrated the population’s favor towards automobiles. During the war, automobile motors, fuel, and tires were in short supply. There was an unsatisfied demand when the war ended and plenty of production capacity as factories turned off the war machine. Many people had saved money because there was little to buy, beyond necessities, in the war years. Workers relied heavily on mass transportation during the war and longed for the freedom and flexibility of the automobile. A historian has said that Henry Ford freed common people from the limitations of their geography. The automobile created mobility on a scale never known before, and the total effect on living habits and social customs is endless. In the days of horse-drawn transportation, the practical limit of wagon travel was 10 to 15 miles, so that meant any community or individual farm more than 15 miles from a city, a railroad, or a navigable waterway was isolated from the mainstream of economic and social life. Motor vehicles and paved roads have narrowed the gap between rural and urban life. Farmers can ship easily and economically by truck and can drive to town when it is convenient. In addition, such institutions as regional schools and hospitals are now accessible by bus and car. Yet, the effect on city life has been, if anything, more prominent than the effect on the farms. The automobile has radically changed city life by accelerating the outward expansion of population into the suburbs. The suburban trend is emphasized by the fact that highway transportation encourages business and industry to move outward to sites where land is cheaper, where access by car and truck is easier than in crowded cities, and where space is available for their one or two story structures. Better roads were constructed, which further increased travel throughout the nation. As with other automobile-related phenomena, the trend is most noticeable in the United States but is rapidly appearing elsewhere in the world. Before the automobile, people both lived in the city and worked in the city, or lived in the country and worked on a farm. Because of the automobile, the growth of suburbs has allowed people to live on the outskirts of the city and be able to work in the city by commuting. New jobs due to the impact of the automobile such as fast food, city/highway construction, state patrol/police, convenience stores, gas stations, auto repair shops, auto shops, etc. allow more employment for the world’s growing population.

The Prime of Miss Jean Brodie Essays

The Prime of Miss Jean Brodie Essays The Prime of Miss Jean Brodie Paper The Prime of Miss Jean Brodie Paper The Prime of Miss Jean Brodie BY prs95 Form is inseparable from content in a work of literature. How do the formal qualities of narratives shape the readers experience of their contents? German philosopher, Immanuel Kant, has supported the statement Form is inseparable from content in a work of literature. He strongly believed that Form without content is empty; content without form is blind. l (page 157) It can be argued that the formal qualities in literature are a key aspect in contributing to the readers overall experience. E. M Forster has suggested that the generic structure of a ovel should entail a beginning, middle and an end. 2 In Muriel Sparks novel The Prime of Miss Jean Brodie, the author has challenged this traditional format through illustrating events in an anachronical form and through the inclusion of a universal omniscient narrator, which has resulted in a build up of suspense, reinforced the novels thematic richness and enabled the reader to recognise the development of characters throughout. Reflecting upon Forsters belief, I would have to disagree with this and feel that Sparks structure has successfully enhanced the readers appreciation of the novel as a whole. On general terms, it seems clear to me that the form of literature is a tool used by authors in order to display the content within the novel in a certain fashion. This will result in the reader interpreting the text in a specific way, driven by the writer. This reflects Kants opinion when focusing on the divorce of form with content. In any novel, and in every aspect of life, time is of paramount importance. In Sparks novel, this facet is manipulated in such a way to be unfamiliar to the reader, yet still providing structure. Despite foreshadowing events of the story, the reader has become intrigued to find out the reasons as to why ertain events occur. Time as a general concept, can be used by writers to emphasise events and regardless of the malleability of time as a structural point, linearity cannot be eradicated completely it fundamentally acts as a structural base for a novel. At the start of the novel, it is immediately clear to the reader that the pattern of time is not in a chronological order, as Spark has included numerous counts of analepsis and prolepsis. This has insistently drawn the reader to a question of time, and it is obvious Spark has explicitly made this a key focal point for the reader. At he first introduction to the Brodie Set, we are informed that the girls are fourth- form (page 5). Following this, there is a flashback to when the girls were age twelve, and then a scene of the girls at the age of sixteen. The individuality of the girls is framed when the reader is told, The five girls, standing very close to each other because of the boys, wore their hats each with a definite difference. (Page 5) Despite sharing the commonality of being a part of The Brodie Set, their differences are highlighted with a flash-forward to how the girls are viewed as individuals later on. Spark has strategically mentioned in the first chapter that Mary Mcgreggor lost her life in a hotel fire (page 14). This key piece of information has signified this event, which has ultimately created a sense of tension, and despite knowing the fate of Mary, the reader almost feels obliged to continue reading. This early foreknowledge one has of Marys fate, affects how the reader views her throughout the remainder of influencing our reading, but anticipation of the event is not strong. (140)3 Looking at this quote, I have already shown a way in which the technique of prolepsis can have strong impact on the reader, however Bridgemans radical statement implying that the readers anticipation is minimal due to the mere knowledge of what happens, I would have to disagree. By simply knowing key events about the content of a novel, the reader begins to actively think about the circumstances surrounding such events, ultimately creating a strong sense of anticipation. Continuing on from Bridgemans view, John Holloway feels that The fact remains that the structure of this narrative is largely a matter of the constant operation of writing a next event so as to negate an xisting forward. 4 (Page 591) He has applied this statement with direct relation to Sparks novel. One may say that this view is too simplistic as it only focuses on the surface of the basic structure. The narrative has foreshadowed many of the events that follow, however the context of these events remains unclear until the story has evolved. There is constant movement within the story, as themes and characters develop. Additionally to Sparks consistent use of prolepsis and analepsis, the form of narrative used has also affected the readers experience of this novel. The main vents of the novel are told through the presence of an omniscient narrator. This has enabled the readers understanding of the main themes of the novel (Miss Brodies Prime and its effect on her pupils) to be deepened. It has created a strong sense of perspective for the reader, and allowed him or her to form an opinion that is not based directly from one of the characters point of view, which is often biased or unreliable. John Morreal has criticised the omniscient narrator, and has said, Omniscience could not provide a filter for a story in the way that the limited knowledge of an internal narrator does. 5 (Page 432) I believe Sparks novel as an example, negates this claim entirely. The style of narrative used, reveals knowledge through the use of prolepsis and analepsis in such a way only to inform the reader of brief, yet vital events. With regards to The Prime of Miss Jean Brodie, if Spark had instead used an internal narrator, the content of the novel would not have been delivered as effectively as it has done with the omniscient narrator, and it would possibly lack its uniqueness. Overall, this has helped shape the readers understanding and experience. The impact of an omniscient narrator can be pplied to other texts, such as Henry James The Turn of the Screw. In this case, the omniscient narrator has been included in order to introduce a sense of uncertainty to the reader, as the narrative form initially seems to lack credibility and reliability. It has presented a perspective that not only links to the uncertainty experienced by the governess herself, but also to influence the outcome the reader takes away from the story. This can therefore draw a likeness to the narrative form in Sparks novel it has been used in order to directly impact the reader. Furthermore, a primary function f a narrative is to tell a story and create a mood, which is achieved in this novel through various language techniques, including speech. The use of direct speech has allowed the reader to gain an insight of characters themselves. Miss Brodie says Give me a girl at an impressionable age, and she is mine for life. This statement, direct from Brodie herself, frames her manipulative personality and her desire to assert control on vulnerable people. The power this has of being direct speech character. It therefore adds a sense of truthfulness to what the reader is told. The ood throughout varies with instances of humour, seriousness and a sense of pity (towards the victims of Brodies manipulation). This constant change in tone creates mixed emotions yet keeps the reader entertained and focused. The reader experiences different emotions whilst forming an impression on Jean Brodie. The use of speech further creates a sense of distance between the reader and Miss Brodie as her character becomes more and more unattractive, however the readers empathy grows for the individual members of the Brodie Set as the harsh effects Brodie has, start to become apparent. Critic Peter Robert Brown has stated that; Readers are encouraged to acknowledge their participation in victimization in the actual world and to reflect on the role that narrative plays in the process and Justification of victimization. 6 (229) This suggestion implies that the readers experiences throughout the novel are somewhat based on their own personal experiences, and a sense of appreciation can be formed based on this. Finally, an important aspect of form, especially with reference to Sparks novel, is the repetition, which emphasises the main themes, fundamentally leading the reader to having a greater ense of the me ssage Spark has aimed to convey. The word prime is mentioned again and again through the course of the novel. In addition to being in the title, and mentioned throughout, the word is even said in the closing sentence of the novel. There was a Miss Jean Brodie in her prime. This is an exact repetition of what Sandy had said earlier on in the novel (page 35). This closing sentence successfully reiterates the theme of ones Prime, and leaves a lasting impression on the reader, allowing him to reflect and create his or her own opinion on what exactly ones prime is, and how Brodies prime affected the girls. Continuing on from the impact repetition has, it almost mirrors the repetitiveness of time itself. This parallel draws attention to the non-linear structure of time, and highlights its individuality. In conclusion, the basic structure of time and unraveling of events has been manipulated a clear representation of the manipulation the girls experience as a consequence of Miss Brodies actions. The formal qualities used by Spark extend further to the narrative technique and aspects such as speech. Looking back at what Forster suggested, Sparks innovative structure has proven successful and has esulted in positively impacting the readers experience of the novel. It has highlighted main themes, reinforced ideas and enabled the reader to recognise the development in characters. With regards to the statement that Form is inseparable from content in a work of literature, it is clear that the two can be differentiated, however they both positively correlate and compliment the purpose and effect each has. Spark has used the form of her work to illustrate the content in order to influence the way in which the reader interoperates certain aspects of the novel.

Getting a Teacher Certificate

Getting a Teacher Certificate As the TESOL teaching profession becomes more and more competitive, finding a good teaching job requires higher qualifications. In Europe, the TESOL teaching certificate is the base qualification. There are a number of different names for this teaching certificate including the TESL teaching certificate and TEFL teaching certificate. After that, teachers who are committed to the profession will usually go on to take the TESOL diploma. The TESOL Diploma is a full years course and is currently highly valued in Europe.    An Overview This main purpose of this diploma (besides, lets be honest, improving career qualifications) is to give the TESOL teacher a broad overview of the principal approaches to teaching and learning English. The course serves to raise the teachers consciousness as to what learning processes are taking place during  language acquisition and instruction. The basis is on an underlying teaching philosophy of Principled Eclecticism. In other words, no one method is taught as being correct. An inclusive approach is taken, giving each school of thought its due, while also examining its possible shortcomings. The objective of the diploma is to give the TESOL teacher the necessary tools to evaluate and apply different teaching methods to meet each students needs. Taking the Course The distance learning method has both its positive and negative side. There is a massive amount of information to get through and it takes quite a bit of self-discipline to complete the coursework effectively. Certain areas of study also seem to play a larger role than others. Thus, phonetics and phonology play a leading role in the makeup of the course (30% of modules and  ¼ of the exam), while other, more practical subjects such as reading and writing, play a relatively minor role. In general, the emphasis is on teaching and learning theory and not necessarily on the application of specific instruction methods. However, the practical part of the diploma does focus very specifically on teaching theory. Logistically, the support and help from Sheffield Hallam and the course directors at English Worldwide were excellent. The final intensive course of five days was essential for the successful completion of the course. This session was in many ways the most satisfying part of the course and served to unify all the various schools of thought studied, as well as providing practical exam writing practice. Advice Self-discipline and good pacing throughout the entire academic year are of absolute importance in order to deal with all the material presented.As the exam itself concentrates not on single areas of instruction, but rather to global issues, relate parts to the whole on a continuing basis.Get some kind of holiday break in before the final intensive week and exam preparation.   Other Experiences The following other articles and accounts of studying for various teaching certifications. A review of the i-to-i Online Tefl CertificateThe British Councils 404 TEFL Qualifications Guide

Survy2222 Essay Example | Topics and Well Written Essays - 250 words

Survy2222 - Essay Example border, drug cash is everywhere in Mexico. The money generated from drugs has propped up the countrys banking system. The money helps the countries ride out the financial crisis and aid the countrys economy. Narcotic drug get smuggled into Mexico mostly from the US at an approximate cost of $100. This money gets to books and accounts of construction firms, bars, and restaurants. Once the money gets settled into such accounts, the police cannot trace it. In western Mexico, drug cartels own hospitals and real estates. In the US as well, drug cartels own big car wash companies. The level of technology and education in the US and Mexico influences the drug trade. The drug cartels are highly organized. The traffickers employ the finest brains. They use the most modern equipment and technologies in producing, transporting, and distributing their drugs. This enables the big drug traffickers to run and finance their operations without into contact with the drugs. This facilitates the drug trafficking business (European Parliament). In the US people with a college education had a lower prevalence of illegal drug use compared to those without a college education. According to Common Sense for Drug Policy, college graduates who used drugs were 5.7 percent. People who had high school education or below and used drugs totaled to 11.2

The Effects of Child Sexual Abuse Research Paper

The Effects of Child Sexual Abuse - Research Paper Example The National Center for Victims of Crime state that sexual abuse can include speaking sexual dialogue to a child, touching their genitals in any way, watching a child when they are naked (voyeurism), rape, including oral or other types of rape, and forcing a child to do sexual acts for performance in pornography or prostitution.This broad definition of sexual abuse gives a better understanding of how children are often exploited without anyone knowing.There is no specific type of person who becomes a child abuser. They can be men and women (though women do not abuse children as often as men), they can be any age, and usually, the perpetrator is in a position of trust (The National Center for Victims of Crime). Some children are victims of incest, which means that someone in their family is either related by blood or the two people have an emotional connection (The National Center for Victims of Crime). Crime statistics show that about 14% of men, who currently are in prison, are chil d sexual abuses. In addition, about 36% of women were abused as children. Child Help also states that 59% of children who have been sexually abused were more likely to be arrested when they are a teenager, 28% more apt to be arrested when they are adults, and they are 30% more likely to commit a violent crime. Children are also more likely to have a sexually transmitted disease as they grow older, and if they have parents who are also alcoholics, they may be more prone to being abused than if the parents do not use alcohol or drugs.

Feminism In England Essay Example | Topics and Well Written Essays - 5000 words

Feminism In England - Essay Example Feminist political activists support such issues as women suffrage, wage equivalency, and have power over reproduction. (O'NEILL, 1969) Feminism is not connected with any specific group, performance, or past occasion. Its foundation is the political understanding that there are rough power arrangements between groups, in conjunction with the faith that something should be done about it. Feminism has been described as a movement with many projects; there is not just one feminist view on everything, so not just one feminist legal theory. However, arguably feminist legal scholars have certain similar concerns. Although anthropologists suggest that many primitive societies were essentially matriarchal, historical evidence from the Roman era till the present time indicates that must legal systems have treated women in an unequal fashion in comparison with their male components. Feminists believe that until the recent past all writing on the social, political, economic, and other major issues affecting humanity have been done by males, from a male point of view and barring very few exceptions (e.g. J.S.Miller), do not reflect women's role in creating and shaping society. Male written works have created and perpetuated biases and injustices against womankind. Male's characteristics are take as the norm and female's characteristics as deviation from the norm. Instances can be quoted to show that the prevailing conceptions and applications of law continue to reinforce and perpetuate patriarchal power. Feminism arose to challenge to rectify these wrongs and the ground realities dictate that the struggle should go on. The 19th century English liberals were among the first jurists seriously to question the position of women in society. For example JS Mill questioned the traditional, to some extent religious view that women were inferior beings destined to obey th eir husbands. Then, towards the end of the century Marxist writers began also to question the way in which women were treated under the law and economically championing women as the oppressed clans. In Marxist eyes it is the male capitalist who is the villain. Women and workers are the oppressed and exploited victims. Modern writers such as Zaretsky attempted to show that male dominance was as much an evil as capitalist oppression (Dixon, 2001). Although most of the leaders of feminist movement were women, yet all women are not the supporters of feminism and not all feminists are women. A number of feminists dispute that men should not acquire positions of headship in the movement, but the majority believe or look for the support of men. The issue of Feminism in England has rose to alarming levels and needs to be addressed so that major revolutions by the women can be avoided. Feminism in England is totally different than that in America as it is based the rights of equality of women their fulfillment and their role in the prosperity of England. The media is playing a major role in influencing the role of women in England. It is portraying women as second class citizens and is

Organic Solar Cells History, Principles and Efficiency

Organic Solar Cells History, Principles and Efficiency Solar Cells Solar cells are cells or devices use for converting sunlight into electric cur ­rent (electricity) or voltage. They are also called photovoltaic cells (PV) or devices and the process of generating electricity from sunlight is called pho ­toelectric effect. Solar Energy conversion through photovoltaic effect can be achieved with many materials at different lifetimes. Over the years many research and development have been conducted in the area of solar energy (thin film applications)[1]-[3]. But most of these developments have been in inorganic solar cells with conventional silicon base solar cells dominating in the production of solar energy in the commercial market [4]-[5]. Silicon base cells for thin film application have enormous advantages like good absorp ­tion rate of sunlight, suitable band gap for photovoltaic applications, longer lifetimes and improving efficiency. But the process of silicon base cells gen ­eration of voltage is tedious and above all very expensive fo r the commercial market. Research for alternatives to silicon has been ongoing for some time now with some other inorganic materials like Copper Indium Gallium Sele ­nium (Cu-In-Ga-Se)[6], Cadmium Sulfide (CdS)[7], Lead Cadmium Sulfide (PbCdS)[8], etc. But some have similar production problems like the silicon and as well expensive. Others also are of dangerous elements which are not environmentally friendly (CdS, PbCdS, etc). Another alternative to silicon base cells in terms of thin film (solar cells) research for photovoltaic applica ­tion could be organic solar cells (also known as plastic solar cells)[9]. With this, photocurrents are generated from organic materials. In this review, brief history of organic solar cells is discussed, the basic principle of operation is outlined and some performance in terms of the materials absorption rate, efficiency, stability and degradation and comparison between organic solar cells and inorganic solar cells (silicon) are also discussed. Chapter 2 Organic Solar cells (Plastic Solar cells) The infancy of organic solar cells began in the late 1950s [10]. At this time, photoconductivity in some organic semiconductor cells (anthracene, chlorophyll) were measured with voltage of 1 V by some research groups[11] ­[12].They proposed that if a single layer PV cell is illuminated consisting of an organic layer, sandwich cell with low work function metal (aluminum, Al) and a conducting glass of high work function (indium tin oxide, ITO), photoconductivity will be observed. With this interesting result and less cost effective of these organic semiconductor cells and also a possibility of doping these materials to achieve more encouraging results caught up with many researchers in this field. The work done since has been unprecedented as shown in figure 2.1 on the next page. In the 1960s, semiconducting properties were observed in dyes partic ­ularly in methylene blue [13]. Efficiency of 10−5 % in sunlight conversion was reported in the early 1970s to an improvement of 1 % in the early 1980s [14]. This was achieved through an interesting phenomenon known as heterojunction[15]. This phenomenon is a surface between semiconduct ­ing materials of dissimilar layers. Photovoltaic devices were applied with heterojunction where donor-acceptor organic cells were tailored together. In recent years, photoconductivity has been measured in dyes and the dye so ­lar cells have progressively been improved for laboratory cells[16]. Currently power conversion efficiency of organic photovoltaics in single-junction devices is over 9 %[17] and that of multi-junction cell is over 12 %[18]. Some materials of organic solar cells are dyes and some polymers like origomers[19], dendrimers[20], liquid crystal materials[21] and self-assembled monolayers [22]. All these need to be prepared carefully to obtain optimum efficiency and stability[23] Figure 2.1: Number of publications is plotted against the year of publications. This shows the inception of organic solar cells and how much interest the field has generated among scientists and the commercial entities over the years. Years below 1990 saw less publication (1960 to 1970 -10 and 1980 to 1990  ­29) compared to the years in the figure. Principle of Operations. In recent time, organic solar cells are of different operations due to their usage. Similar to inorganic solar cells, organic solar cells can be used to convert sunlight into electricity with the aid of a semiconductor. The basic principle behind this operation is outline below: Most organic solar cells have very thin material layer either single or multi-layer where there is a strong absorption of light sandwich between two electrodes, an anode (A) and a cathode (C). The anode (usually indium tin oxide ITO) is transparent and has a high work function. The cathode (aluminum) is opaque and has a low work function. The material layer is usually a photosensitive organic semiconductor. When light of appropriate energy (sunlight) is incident on it, an electron is excited from the highest occupied molecular orbital (HOMO) to a lower uncopied state called lowest uncopied molecular orbital (LUMO) leaving a hole in the HOMO. This leads to exciton formation. That is, there is a creation of an electron-hole pair which is strongly bounded together. As the electron stays at the LUMO, there is a loss in energy by the electron through thermal relaxation as the electron penetrates the energy band gap. The electron-hole pair diffuses in ­dependent of the electric field and are separated (exciton dissociation) at the interface between the donor state (HOMO) and the accepter state (LUMO). The electron is collected at one end of the electrode (cathode) and the hole at the other end of the electrode (anode) thereby generation photocurrent in the process. If the electron and the hole after separation do not reach the interface, their absorbed energies are dissipated out and no photocurrent is generated. Step by step principle is illustrated in pictorial form below: Figure 3.2: a) Light is incident on an electron (red). (b) Electron is excited from the HOMO to the LUMO creating a hole (black) at the HOMO. (c) Exciton formation of electronhole pair. (d) Diffusion of exciton independent of electric field. (e) Exciton dissociation. (f) Collection of charges. Chapter 4 Performance 4.1 Absorption of light. In organic solar cells, the thin organic semiconducting layer is responsible for light absorption. This layer has a valence band which is densed with electrons and a conduction band. These bands are separated by an energy gap. When the layer absorbs light, an excited state is created. This state is characterized by an energy gap. The energy gap is the energy difference between the higher energy state (LUMO) and the lower energy state (HOMO). It is usually of the range of (1.0 -4.0) eV[24] and it is determined as: Eg = ELUMO − EHOMO . (4.1) Where Eg is the energy gap in electron volts (eV), ELUMO is the energy at LUMO (higher energy state) and EHOMO is the energy at HOMO (lower energy state). The energy gap usually serves as an activation energy barrier. This acti ­vation energy barrier needs to be overcome before an electron is excited from the lower energy state to the higher energy state. The excited electron has energy greater than or equal to this activation energy barrier. This energy is determined as: h.c Ephoton = ≠¥ Eg . (4.2)ÃŽ »photon Where Ephoton is the energy of the incident photon (light), h is Plancks constant (6.626 Ãâ€"10−34 Js), c is speed of light (2.997 Ãâ€"108 ms−1) and ÃŽ »photon is wavelength of the photon (≈ (400 -700) nm). As the excited electron remains at the LUMO, a hole is created in the HOMO. The electron undergoes thermal relaxation as it remains at the LUMO and this result in loss of energy by the electron. This energy loss is compensated for as: El = Eelectron − Eg . (4.3) Where El is thermal energy loss of the electron, Eelectron is the energy of the electron at the LUMO and Eg is the energy gap. Figure 4.1: (a) Thin organic semiconductor layer (with both LUMO and HOMO) with energy gap (Eg). (b) Incident light of greater energy than the energy gap excites electron (red) from HOMO to LUMO. This creates a hole (black) at the HOMO (c) Energy lost by the electron through thermal relaxation. 4.2 Stability and Degradation In solar cell application, long operational lifetime performance is required. To achieve this, stability and degradation are few of the key important issues to look at in real-time application. Over the years, stability of organic solar cells has improved very much in terms of their power conversions[25]. This is clearly shown in the figure below: Ideally the advantages of organic solar cells with their low cost materi ­als, recyclable, easy production and production in large quantities, à ¯Ã‚ ¬Ã¢â‚¬Å¡exibility and durability (low weight), stability should be optimum. These advantages somehow also affect the stability of the organic cells. The active layer (thin organic semiconducting layer) component which is a core component of the cells is sometimes prone to degradations. These degradations occur dur ­ing their production (printing in bulk quantities and rolling them together thereby introducing some mechanical properties which then affect the mor ­phology of the active layer) and also reactions from weathering (UV light, oxygen, water). Extensive work on photo stability of some organic solar cells (large number of polymers) has been investigated by Manceau et al[27]. Figure 4.2: Organic Photovoltaic (OPV) production with progression in years shown. The years below 2010 had lower production of OPVs (> 0.5 MW) [26]. Chapter 5 Comparism between organic solar cells and inorganic solar cells (Silicon base solar cells). Organic and inorganic solar cells serve similar applications but they interest ­ing differences in terms of how they are made. Organic solar cells are cheap in terms of materials, production and are recyclable, they have very thin solar cells with little energy in making them, they are à ¯Ã‚ ¬Ã¢â‚¬Å¡exible, durable and have low weight, they are colourful and they have easy production and can be produced in large areas. But they have low efficiency and lifetime compared to silicon base solar cells. Inorganic solar cells are cost effective in terms of materials, production and are not recyclable, much energy is need to have thin layer cells, they are rigid and not durable, they are of dark grey materials with dark blue to black coat ­ing, they have complicated production and are difficult to produce in large areas. But they have good light absorption rate, better efficiency and longer lifetime. Chapter 6 Conclusion Organic solar cells can be alternative to silicon base solar cells with its in ­teresting applications. They can be fabricated into our day to day usage materials and equipment with low cost technology in serving their purpose. Efficiency and stability still remains areas that should be addressed in the future to optimally have good power conversions.