Solar photovoltaic pv cells san jose state university. Feb 07, 2018 there is no difference in a p n junction and solar cell infact solar cell is a type of p n junction diode the only special character of solar cell it that one of the region p or n is made very thin so that the light reaches the depletion regi. The intention is top convert the incoming optical power into electrical power with maximum efficiency 4. However the electric field, a oneway downhill road superimposed across the cell, allows the electrons to flow only in one direction. A p n junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. V principle of solar cell v current generation v iv characteristic of an illuminated pn junction v physical process of solar cell v iv characteristic of solar cell v solar cell parameter v applications v reference v device that converts optical energy into electrical energy. Before we can design p n junction devices that couple electricity to light and vice versa we need. This section will cover pn junction diodes, which are essential to solar cell operation. There is no difference in a pn junction and solar cell infact solar cell is a type of pn junction diode the only special character of solar cell it that one of the region p or n is made very thin so that the light reaches the depletion regi. The pn junction that is formed by two chemically different semiconductors is called the pn heterojunction. The journal of physical chemistry letters, 0 proofing doi.
A solar cell is basically a semiconductor pn junction device. When light reaches the pn junction, the light photons can easily enter in the junction, through very thin ptype layer. Solar cell design issues a schematic of a simple conventional solar cell. A closer look at the opencircuit voltage if a pn junction has an external forward bias voltage applied across it, a current will flow through the junction of the solar cell from the ptype side to the ntype side conventional current. Then, current solar cell design and performance will be presented, and future design. Pdf design and simulation of ingan p n junction solar cell. In order to find an upper theoretical limit for the efficiency of p. When electrons all move the same direction then you have electricity. Single junction solar cells the plain and simple solar. It is formed by joining ptype high concentration of hole or deficiency of electron and ntype high concentration of. The theory of solar cells explains the process by which light energy in photons is converted into electric current when the photons strike a suitable semiconductor device. In practice, pn junctions of silicon solar cells are not made in this way, but rather by. Solar cells solar cells are i n photodiodes, which are operated under forward bias. The light energy, in the form of photons, supplies sufficient energy to the junction to create a number of electronhole pairs.
The optimized cells showed a device ideality factor close to unity and a record. Application of p n junctions within solar cells is discussed. This pair is separated by an internal electrochemical potential present in pn junctions or schottky diodes and the resulting flow of electrons and holes creates electric current. The pn junction is a versatile element, which can be used as a rectifier, as an isolation structure and as a voltagedependent capacitor. The doping is normally applied to a thin layer on the top of the cell, producing a p n junction with a particular bandgap energy, e g.
Shockley model from sze, 1981 vv at 1 j j e tot s n n p p p n s l d n q l d p j 0 0 j j x j x tot n p p n a i n n n d n q 2 w p n. A photodiode is a light detector that operates in reverse bias. Junction solar cell an overview sciencedirect topics. Solar cells generate electricity owing to the presence of pn junctions. Conventional pn junction photovoltaic cell hot charge carriers e hole loses. What is a p n junction, what are single junction solar cells, and how are they different from multi junction solar cells. Individual solar cell devices can be combined to form modules, otherwise known as solar panels. Cells are typically made using a crystalline silicon wafer. Sep 29, 2015 pn junction as solar cell baquer mazhari. Record high efficiency singlewalled carbon nanotube. Schematic diagrams of a conventional pn junction solar cell left and an organic heterojunction solar cell right. The conventional solar cells being used in solar power plants are of the single junction type, and generate electricity using the single p n junction. Pn junction diodes form the basis not only of solar cells, but of many other electronic devices such as leds, lasers, photodiodes and bipolar junction transistors bjts.
Surface passivation and contact optimization will be critical to improve device performance in the future. Part 6 photodiodes, solar cells photovoltaic devices, and multiple diode analysis reading. The theoretical studies are of practical use because they predict the fundamental limits of a solar cell, and give guidance on the phenomena that contribute to losses and solar cell efficiency. In the past, various kinds of semiconductor materials and technologies are devised to design solar cells with. Eele408 photovoltaics pn junction solar cell in equilibrium. It supplies a voltage and a current to a resistive load light, battery, motor.
When light shines on them they can generate current and voltage. An overview focusing on active layer morphology travis l. We give the upper limit to the solar cell e ciency. When an atom like phosphorus, with more than four bonding. They are also called p n diodes in analogy with vacuum diodes.
A solar cell is basically a semiconductor p n junction device. To learn more on the formation, forward and reverse bias, with formula, visit byjus. In typical solar cell applications there is about 1 dopant atom for every 5,000,000 silicon atoms. Consists of a largearea, single layer pn junction diode. Apr 03, 2017 the junction attracts electrons one side and repels them the other side, making electrons all move the same direction in the junction area. Solar cells generate electricity owing to the presence of p n junctions. What kind of devices can we build using p n junctions. A closer look at the opencircuit voltage if a p n junction has an external forward bias voltage applied across it, a current will flow through the junction of the solar cell from the p type side to the n type side conventional current. Solar cell free download as powerpoint presentation. When photons hit the solar cell, free electrons attempt to unite with holes in the ptype layer. Denis ar con ljubljana, may 2011 abstract this seminar is a short overview of current photovoltaics. Due to the pn junction, a built in electric field is always present across the solar cell. It is important to learn the basic properties of semiconductor and the principle of conventional pn junction solar cell to understand not only the conventional solar cell but also the new type of solar cell.
They are also an essential part of metaloxidesilicon fieldeffects. The common single junction silicon solar cell can produce a maximum opencircuit voltage of approximately 0. The theoretical studies are of practical use because they predict the fundamental limits of a solar cell, and give guidance on the phenomena that contribute to losses and solar cell efficien. The spectrum as seen from a satellite is referred to. Ch4 solar cell operational principles tu delft ocw. It is formed by joining p type high concentration of hole or deficiency of electron and n type high concentration of. It is a pn junction structure with full back metallization and partially metallized front to allow the passage of light to the semiconductor while collecting the cell current. The conventional solar cells being used in solar power plants are of the singlejunction type, and generate electricity using the single pn junction. Light photon energy electric energy silicon solar photovoltaic cells a device made of semiconductor materials that produce electricity under light a pn junction is created in silicon by a doping process. Light photon energy electric energy silicon solar photovoltaic cells a device made of semiconductor materials that produce electricity under light a p n junction is created in silicon by a doping process. He turned to calvin fuller for advice on creating a solar cell that would permanently fix the pn junction very the atomic battery, according to rca, would some day power homes, cars, and locomotives with radioactive waste. The functioning of a solar cell is similar to the photodiode photodetector. At first, fundamentals of photovoltaics and the basic features of multi junction solar cells will be described. The n region is heavily doped and thin so that the light can penetrate.
First consider what happens if a silicon solar cell which is a p n junction has a low. Single junction solar cells the plain and simple solar cell. Questions you should be able to answer by the end of todays lecture. In this study ge and ingaas single junction solar cells which are used as the bottom cell of triple junction solar cells are investigated 4. A solar cell is a solidstate electrical device p n junction that converts the energy of light directly into electricity dc using the photovoltaic effect. This expression only includes the ideal diode current of. The generation of voltage difference noticed at the p n junction of the cell in res ponse to visible radiation is ut ilized to do the work.
Effect of series resistance on the iv characteristic of a solar cell. In partial fulfillment of the requirements for the degree of. To measure the reflectivity of the pn junction cell with and without indents, a. A pn junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. This question is part of the super big solar panel faq from solar mango, where expert answers to over 100 important questions on solar panels are provided. The current through the solar cell can be obtained from. Mono crystalline solar cell, as the name indicates, is manufactured from single crystals of silicon by a process. P n junction diodes form the basis not only of solar cells, but of many other electronic devices such as leds, lasers, photodiodes and bipolar junction transistors bjts. The reason this can happen is because of the builtin electric field at the junction of the ptype and ntype material. A typical csi solar cell structure is shown in figure 3. In the pin junctions, the region of the internal electric. A diode is an electronic component that consists of a pn junction, just like a solar cell, except that it has a much smaller surface and the. When light reaches the p n junction, the light photons can easily enter in the junction, through very thin p type layer.
May, 20 in the following paragraphs, a simple introduction of a solar cell and how it operates is discussed, with reference links for better understanding. Pdf a solar cell is an electronic device which directly converts sunlight into electricity. Consists of a large area, single layer pn junction diode. The junction attracts electrons one side and repels them the other side, making electrons all move the same direction in the junction area. Pdf the tunability of the ingan band gap energy over a wide range provides a good spectral match to sunlight, making it a suitable material for. What is the exact working of a pn junction in a solar panel. The solar spectrum the solar spectrum is shown in figure 4. The area where electricity is first generated in a semiconductor, such as a solar cell. A pn junction is used for charge carrier separation in most cases.
V principle of solar cell v current generation v iv characteristic of an illuminated p n junction v physical process of solar cell v iv characteristic of solar cell v solar cell parameter v applications v reference v device that converts optical energy into electrical energy. A detailed balance analysis of conversion efficiencies limits for nanocrystal solar cells relating the shape of the excitonic peak to conversion efficiencies j. The p n junction is a versatile element, which can be used as a rectifier, as an isolation structure and as a voltagedependent capacitor. What happens when we join ptype and ntype semiconductors. What is a pn junction, what are single junction solar cells, and how are they different from multijunction solar cells. In the following paragraphs, a simple introduction of a solar cell and how it operates is discussed, with reference links for better understanding. Solar cell unbiased photodiode light nolight i v since npno and pnpo at the. Solar cells are described as being photovoltaic, irrespective of whether the source is sunlight or an artificial light. At first, fundamentals of photovoltaics and the basic features of multijunction solar cells will be described. A solar cell is a solidstate electrical device pn junction that converts the energy of light directly into electricity dc using the photovoltaic effect. Most common approaches to model a p n junction solar cell are detailed balance model dbm and driftdiffusion model ddm. What is the difference between the pn junction and a solar cell.
Working principle of silicon solar pv cells photovoltaic material of device converts. Part 6 photodiodes, solar cells photovoltaic devices, and. Aug 30, 20 how does a p n junction solar cell work. The construction, of a pn junction solar cell is shown in fig. A detailed balance analysis of conversion efficiencies limits for nanocrystal solar cellsrelating the shape of the excitonic peak to conversion efficiencies j. Record high efficiency singlewalled carbon nanotubesilicon. Photons that hit the top of the solar cell are either reflected or transmitted into the cell. The theory of solar cells explains the process by which light energy in photons is converted into.