A typical csi solar cell structure is shown in figure 3. Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon. A solar cell made of just one material cannot be more than about 30% efficient in theory and below around 25% in practice. Preparation of cu2ozno pn junction by thermal oxidation. The use of multiple semiconducting materials allows the absorbance of a broader range of wavelengths, improving the cells sunlight to electrical energy.
Province natural science foundation young talent program no. A study on the electrical characteristic analysis of csi solar cell diodes pyungho choi, hyojung kim, dohyun baek, and byoungdeog choi abstracta study on the electrical characteristic analysis of solar cell diodes under experimental conditions of varying temperature and frequency has been conducted. Insight into interfaces and junction of polycrystalline. Solar cells convert light energy into electrical energy either indirectly by first converting it into heat, or through a direct process known as the photovoltaic effect. While the current industry average for solar panels is 1218% efficiency, the latest multi junction cells already offer efficiencies of 40% for example, these 40% efficiency solar cells from boeing subsidiary spectrolab. Since the n type region has a high electron concentration and the p type a high hole concentration, electrons diffuse from the n type side to the p type side. However the electric field, a oneway downhill road superimposed across the cell, allows the electrons to flow only in one direction. Multijunction mj solar cells are solar cells with multiple pn junctions made of different semiconductor materials. The animations below represent p type and n type silicon. Photons that hit the top of the solar cell are either reflected or transmitted into the cell. The process of conversion first requires a material which absorbs the solar energy photon, and then raises an electron to a higher energy state, and then the flow of this highenergy electron to an external. Solar cell interfaces pn junction abstract kelvin probe force microscopy kpfm is a powerful tool to measure surface potential with resolutions in the order of atomicnanometer scales, and could also provide direct measurements of the surface potential on interfaces and junctions of solar cell devices. Watch the full video first and you will get a clear idea about the working of solar cells.
A collection of resources for the photovoltaic educator. A solar cell utilizes the concept of a p n junction in capturing the solar energy. You would have likely heard about the pn junction of the solar cell, which is in fact the junction that. Stronger ohmic shunts locally shortcircuit the pn junction. Single junction solar cells the plain and simple solar cell technology. A photovoltaic device produces a current or a voltage at its output in the presence of light. For am1 normal incidence the power density is reduced to 925 wcm 2 whereas for am1. Since the ntype region has a high electron concentration and the ptype a high hole concentration, electrons diffuse from the ntype side to the ptype side.
The process of conversion first requires a material which absorbs the solar energy photon, and then raises an electron to a higher energy state, and then the flow of this. Similarly, holes flow by diffusion from the ptype side to the ntype side. Concentrated photovoltaic cpv system is usually located in sunny places for largescale photovoltaic pv power station with installation capacity of 1 megawatt mw. These twoemerging industries based on pn junctions make a significantcontribution to the reduction in fossil fuel consumption. What weve drawn here is basically a silicon solar cell, so, like the one i have here. The following figure shows the fermi level of a semiconductor. Single junction solar cells have just one pn junction, as against multi junction solar cells, which have more than one pn junction solar cells generate electricity owing to the presence of pn junctions. Practical evaluation of solar irradiance effect on pv. For a semiconductor to conduct, electrons must cross the energy gap from the valence band to the conduction band. Prior to any deposition step, the itoglass substrates were polarized by applying a 10 macm2 current for 60120 s in 1 m naoh in order to create a higher density of nucleation sites and therefore. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. When the lightgenerated minority carrier reaches the pn junction, its swept across the junction by the electric field at majority carrier the junction.
The radial pn junction design sets the direction of light absorption perpendicular to the direction of minoritycarrier transport, allowing the cell to be thick enough for e. This model can be used further for studying properties of advanced devices like multijunction solar cells. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Photocurrent in pn junction solar cells flows in the diode reverse. A solar cell is a solidstate electrical device pn junction that converts the energy of light directly into electricity dc using the. When light reaches the pn junction, the light photons can easily enter in the junction, through very thin ptype layer. And after that well go into organic solar cells where the pnjunction is formed in a completely different way. The iv curve of a solar cell is the superposition of the iv curve of the solar cell diode in the dark with the lightgenerated current.
In the next week well talk about silicon solar cells. At first, fundamentals of photovoltaics and the basic features of multi junction solar cells will be described. Feb 01, 2014 fabrication of solarphotovoltaic cell basically a solar cell is a junction usually a pn junction with sunlight shining on it. Aug 30, 20 how does a p n junction solar cell work. Single junction solar cells the plain and simple solar cell.
The irregularities in the spectrum are due to absorption at specific photon energies. We present here a computer program the semiconductor device simulator which simulates the working of three pn junction devices the led, the solar cell, and the tunnel diode. The p n junction is the fundamental building block of the electronic age. Animation how a p n junction semiconductor works forward reverse bias diffusion drift current. 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.
A solar cell is essential a pn junction with a large surface area. Then, current solar cell design and performance will be presented, and future design. Their energy conversion efficiency was mainly affected by the quality of cu2o and zno layers, and the interface of pn junction. A study on the electrical characteristic analysis of csi. The conventional solar cells being used in solar power plants are of the singlejunction type, and generate electricity using the single pn junction.
Multi junction solar cells are the future of pv solar electricity generation. What is a pn junction, what are single junction solar cells, and how are they different from multi junction solar cells. Although the term panel is still widely used, its more accurate to say module when referring to a rectangular unit of solar cells encased in an aluminum frame. A solar cell basically is made by a p n semiconductor junction and when exposed to light, a dc current is generated. The solar cell under illumination in the dark, the energy supply comes from outside of the cell via the applied voltage, and under illumination, the energy supply occurs inside the cell via photogeneration of electronhole pairs, see the figure above.
Atmospheric effects azimuth angle bias of pn junctions bulk lifetime buried contact solar cells czochralski silicon declination. If transmitteremitter and base of the solar cell are connected together i. Their energy conversion efficiency was mainly affected by the quality of cu2o and zno layers, and the interface of p n junction. Solar cells generate electricity owing to the presence of p n junctions. A solar cell is a solidstate electrical device pn junction that converts the energy of light directly into electricity dc using the photovoltaic effect. Progress and challenges for nextgeneration highefficiency.
These novel device structures are potentially useful for advanced solar cell applications. The pn junction is the fundamental building block of the electronic age. Equation of iv characteristics of pn junction diode. Principles of solar cells, leds and diodes covers the twomost important applications of semiconductor diodes solar cells and leds together with quantitative coverageof the physics of the pn junction. A major driver in the progressively lower cost of photovoltaic power is the. An easytounderstand explanation of how solar cells turn sunlight into. The development of nanowire arrays in the past decade has opened the door for fabricating highly efficient solar cells. Chapter 7 solar cell universiti tunku abdul rahman. Expressed in a different form, the ratio of minority to majority carriers is less than one person to the entire population of the planet. Solar cell interfaces p n junction abstract kelvin probe force microscopy kpfm is a powerful tool to measure surface potential with resolutions in the order of atomicnanometer scales, and could also provide direct measurements of the surface potential on interfaces and junctions of solar cell devices. We have used partial differential equations for modeling the pin photovoltaic system.
Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Therefore researchers came up with multijunction solar cells. Illuminating a cell adds to the normal dark currents in the diode so that the diode law becomes. While photovoltaic action readily takes place in a number of materials, the third. Iscvoc pmax maximum power pt theoretical power efficiency is the ratio of the electrical power output, compared to the solar power input, into the solar cell. Solcore was born as a modular set of tools, written almost entirely in python 3, to address some of the task we had to solve more. Solar cells are a form of photoelectric cell, defined as a device whose electrical characteristics.
Detailed balance limit of efficiency of pn junction solar cells. Yastrebova, centre for research in photonics, university of ottawa, april 2007. Improving the efficiency of solar cells through novel materials and devices is critical to realize the full potential of solar energy to meet the growing worldwide energy demands. High efficiency silicon solar cell based on asymmetric. The solar cell converts photon power into electrical power by generation of electronhole pair ehp and delivers this power to a load. In a typical solar cell, one side of the cell is doped with boron the p type, and the other side n type is doped with phosphorus. Silicon a single silicon atom consists of fourteen negatively. Design of multijunction solar cells using pc1d request pdf. The light energy, in the form of photons, supplies sufficient energy to the junction to create a number of electronhole pairs. Ppt applications of photovoltaic technologies powerpoint. A multijunction solar cell is made up of a two or more layers of semiconductor material for example, one layer that can absorb blue light well, and a second layer. You learned on the role of a p n junction page that the voltage difference between the two contacts is equal to the splitting of the quasifermi energies. Multiple materials solar cells with different bandgaps that covers a range of the solar spectrum achieved the highest efficiency conversion. Single junction solar cells have just one pn junction, as against multijunction solar cells, which have more than one pn junction.
It is composed of fresnel lenses to concentrate, iiiv multi junction solar cells, polar axis type or pedestal type tracking system and integrated control method. Solar cells generate electricity owing to the presence of pn junctions. Weve come a long way to gain an understanding of semiconductors to see how they relate to making solar cells. A solar cell basically is made by a pn semiconductor junction and when exposed to light, a dc current is generated.
A solar cell utilizes the concept of a pn junction in capturing the solar energy. Solar cell animation when energy is received from the sun in the form of photons, some of the photons are absorbed near the junction, freeing the electrons and holes in the silicon. As solar cell manufacturing continues to grow at a recordsetting pace, increasing demands are placed on universities to educate students on both the practical and theoretical aspects of photovoltaics. Fabrication of solar cells the first practical photovoltaic cell was developed in 1954 at bell laboratories. F hg i b 1kj where io reverse saturation current, q electronic charge 1. A typical pn junction solar cell was constructed as follows.
When photons hit the solar cell, free electrons attempt to unite with holes in the ptype layer. P n junctions are formed by joining n type and p type semiconductor materials, as shown below. To understand how the pn junction works, please watch the following video 10. What is a pn junction, what are single junction solar cells, and how are they different from multijunction solar cells. 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. Diodes are semiconductor devices that allow current to flow in only one direction. Progress and challenges for nextgeneration highefficiency multijunction solar cells. The solar spectrum as observed on earth is modified due to absorption in the atmosphere. If you have any doubt about the working principle of solar. Due to the pn junction, a built in electric field is always present across the solar cell. Instructor information ress program creating a presentation. Light shining on the solar cell produces both a current and a voltage to generate electric power. You learned on the role of a pn junction page that the voltage difference. Fabrication of solarphotovoltaic cell basically a solar cell is a junction usually a pn junction with sunlight shining on it.
The photons of light give enough energy for the electrons to cross the junction, where they can be picked. We present here a highly efficient radial pn junction silicon solar cell using an asymmetric nanowire structure with a shorter bottom core diameter than at the top. What is a p n junction and how does it work to generate electricity. You would have likely heard about the pn junction of the solar cell, which is in fact the junction that generates the photovoltaic current. With time, however, it has evolved as a complete semiconductor solver able of modelling the optical and electrical properties of a wide range of solar cells, from quantum well devices to multi junction solar cells.
When light is incident on a solar cell, carriers get generated at that surface, but not in the bulk of the solar cell. This is shown in the animation below in which one region of the device has a high concentration of electrons and the. Understanding junction breakdown in multicrystalline solar cells otwin breitenstein 1, jan bauer 1,a, karsten. 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. It is composed of fresnel lenses to concentrate, iiiv multijunction solar cells, polar axis type or pedestal type tracking system and integrated control method. The most common types of solar cells are based on the photovoltaic effect, which occurs when light falling on a twolayer semiconductor material produces. 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.
Understanding junction breakdown in multicrystalline solar. It supplies a voltage and a current to a resistive load light, battery, motor. In a typical semiconductor there might be 10 17 cm3 majority carriers and 10 6 cm3 minority carriers. Solar energy accounts for most of the usable renewable energy on. And after that well go into organic solar cells where the pn junction is formed in a completely different way. Each materials pn junction will produce electric current in response to different wavelengths of light. Solar cell how a solar cell works, solar cell animation. Single junction solar cells the plain and simple solar. What is a p n junction, what are single junction solar cells, and how are they different from multi junction solar cells. 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. They used a diffused silicon pn junction that reached 6% efficiency, compared to the selenium cells. It as it radiation flux as surface area of pn junction v there are no fuel costs or fuel supply problems v the equipment can usually operate. Understanding light harvesting in radial junction amorphous.
One side of a solar cell is doped with boron, the p type, and the other side with phosphorus, the ntype, creating a single pn junction. One type is called the p type and the other is called the n type. A solar cell with a bulk doping concentration of 1016 cm3 should show under reverse bias a saturation current in the order of. When connected in series or in a row, installers in the field will refer to the several modules as a solar panel. The ntype material is kept thin to allow light to pass through to the pn junction. This program enables students to create the device starting with two pieces of intrinsic semiconductor material, and doping them appropriately to create a pn. This causes the current to reverse its direction under illumination. Queisserdetailed balance limit of efficiency of pn junction solar cells. Suppose now that we are aiming to make a solar cell junction with a bandgap that differs from that of the latticematched.