Dear Halim,

the topic you ask is of great interest to the layman. However, the language you use, while being very technical, is understandable.

From aninterdisciplinary point of view, please see one of our connected papers which reached 320 views 76 downloads.

Kindest regards

Marg

Conference Paper THE SOLAR AGE: UTOPIA AND DYSTOPIA. HOW TO TRANSFORM GREEN W...

Solar cells on calculators and satellites can see, with photovoltaic cells or "photovoltaic" are known. The name originated from the photo means light and voltaic means electricity, the cells that convert sunlight directly to electricity. A module consists of a group of cells electrically connected and the frame is mostly known as a solar panel. These materials can be noted that silicon is very good. When light strikes the cell, in principle, a certain amount of it is absorbed by the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor.sends them in a certain direction. This process, along with the voltage within the cells (as a result of field or electrical field is created inside cells) or voltage power generated by a solar cell. This defines the basic process that occurs in a solar cell, But the reality is much more complex, and more. Went on to form a closer and deeper look at the throw of a photovoltaic cell, a silicon cell.

How silicon solar cells will become.

Silicon some special and unique chemical properties. In particular, in the crystalline state. A silicon atom has 14 Lktrvn sorted in three different layouts. The first layer two and eight are completely full. Layer or outer shell is filled only half the capacity of four electrons. Silicon atoms are always looking for ways to complete their final layer. And to do their electrons with four atoms sharing her side. Such that each atom adjacent atoms together and unite with its four neighbors.

The only problem is that pure crystalline silicon is a poor conductor of electricity because, unlike conductivity material such as copper, none of its electrons are free to move electricity. To solve this problem, the silicon used in solar cells combined with some other atoms and impurities in some way alter the silicon atoms. Silicon with a small amount of phosphorus atoms imagine. Perhaps a million atoms per silicon atom. 4 electrons in its outer layer, unlike silicon, phosphorus, 5 electrons. But with its neighbor silicon bonded and formed an alliance. But the logical form, phosphorus is a free electron that is not connected to nowhere. And is not a member of any alliance. But the positive protons in the nucleus of P that holds it in place.

When energy is added to pure silicon, for example in the form of photons, electrons will cause some bands and their relationships to break free. And after each failure, a hole remains. These electrons are "free carriers" are called and then randomly within the crystalline lattice of the crystal will be wandering and looking for another hole to fall into it and conduct electrical current. However in a few of these are pure silicone, which can be very useful.

But impure silicon with phosphorous atoms of a different story. This combination requires less energy to an electron excess phosphorus from it. Because they are not connected to the place and not share with other atoms. As a result, many of these electrons can easily break. As a result, compared to pure silicon, we have a lot more free carriers. Add impurity doping process is called and when it will be done by P N-type silicon produced by this process say the word n is a negative word. Because it will cause a loss of electrons. Condensed silicon N-type conductivity is much better than pure silicon.

The other part of conventional solar cells, silicon is condensed with the element boron. Boron has only three electrons in its outer layer. In this case, the P-type silicon is known that the word is Positive. For the final layer of silicon vacancy for an electron and a positive charge carriers are attracted.

Let's see when the two parts together and interact with each other are what happens.

We now know that two separate silicon electrical nature. But the interesting thing is that when you start to put them together. Without an electric field, the cell does not work. When the field is formed by P-type and N-type silicon in contact with each other. Suddenly, the free electrons fill all empty holes? No. If this happens, it is very helpful and useful apparatus will be. But right at the junction, they combine to make a dam. As a result of the passage of electrons from the moment they arrive to the N and P are harder and harder. The equilibrium is established. We have an electrical field to separate the two sides.

The electric field as a "diode" acts and allows electrons (and they will) to flow from the P to the N side. But on the contrary will not move. This is just like a hill that electrons can easily take it down (the N) but could not climb it (the P).

When a photon of light hits the solar cell, the energy of the electron-hole pairs from shattering. Each photon with sufficient energy can usually release an electron. Provide a way to see if the output current, electrons flow from the P to the electrical unit and do what we want to do. Circulating flow of electrons and electric field causes the cell voltage is generated. With current and voltage, we will have the power to both the product.

Still other electrical components remain until we can really use our solar cells. Very bright silicon materials that can absorb photons before they do they will be reflected.

An anti-reflection coating is necessary to minimize losses. The final step is to install something that protects the cells against the environment. The protective glass is often a coat of talc. Several photovoltaic modules are connected to each other to achieve an acceptable level of individual cells and the applicability of current and voltage are made. And placing them in a strong frame with the positive and negative terminals are full story.

Now how much solar energy photovoltaic cells absorb? Unfortunately, this level may be too high. For example, in 2006, most solar panels only yields were 12 to 18 percent. What is now considered as the most efficient solar cells and has a record for efficiency, 40 to 40.7 percent.

Dissipation of energy in a solar cell

The only visible part of the electromagnetic spectrum. Monochromatic electromagnetic radiation is composed of a range of different wavelengths and thus different energy levels.

Can be decomposed into different wavelengths of light that we can see the rainbow. Since our cells with the photon energy range shot is different, so some of them do not have the energy to break bonds electron-hole. They simply pass through the cell, just like that of a transparent glass crossed. While some of the photons have a lot of energy. Only a certain amount of energy, which is measured in electron volts (the amount is determined for the material inside our cells) can affect the electrons in the atoms of our silicon solar cell. We call this the band gap energy. If the photon energy is greater than the required amount, the excess energy is wasted. This means that almost 70% of radiant energy received by our cells actually die and performance.

Why can not we choose materials that have a low band gap and take advantage of more photons? Unfortunately, our band gap voltage electric field strength or our time is limited and if it is too low, the flow that is generated by absorbing more photons, will produce much lower voltage. And the most efficient way possible to generate voltage and current is flowing.

We also have other losses in the meantime. We electrons by an external circuit from one side to the other cells will flow. We can provide good conductivity below and we covered with metal. But if you completely cover the upper part, the photons can pass through opaque conductive and we are all going to be completely lost. In some solar cells on top of transparent conductors are used. If our points of contact in our cell walls. Electrons can be really long way to reach the contact points within them. Keep in mind that silicon is a semiconductor and metal as the flow do so. And the relatively high internal resistance. And high resistance means high energy dissipation. To minimize this loss, the cells cover the distance traveled by the electrons in the metal lattice points of contact to a minimum. Of course, this also leads to blockage of photons which, although not very low, but the internal resistance of semiconductors is much less.

Now you know how a solar cell works. Let Bbyynym how energy can be supplied in a house with this technology.

House with solar energy

Solar energy to power our homes and what we need? Although it is not as simple as installing multiple modules on the roof of the house. And of course, it's not much different.

First of all, all the rooftops to the proper angle and slope are required to make full use of sunlight. Fixed photovoltaic systems that can track the sun does not have to be installed at the most appropriate time of day and the maximum duration of benefit from direct sunlight. The house used in the winter or summer. And certainly not by a panel of shade trees around the house or neighboring houses are covered.

If your roof is in good, now it is your choice to decide on the size of your system. This issue becomes more complex when the other facts in the story of our involvement. For example, the generation of electricity that is not dependent on the weather, it can not be predicted. Or if your electricity consumption is quite variable.

Dear Halim,

the topic you ask is of great interest to the layman. However, the language you use, while being very technical, is understandable.

From aninterdisciplinary point of view, please see one of our connected papers which reached 320 views 76 downloads.

Kindest regards

Marg

Conference Paper THE SOLAR AGE: UTOPIA AND DYSTOPIA. HOW TO TRANSFORM GREEN W...

Dear Sir,

I encountered a problem that when analysing the GaAs p-n+ diode, I found its ideality factor is around 2.5.Is this possible? If so, what's the main reason?

Dear Siwei,

Welcome,

At first you have to check if your metal - semiconductor contacts are ohmic using the the three probe method introduced in my paper in the question.

If it is nonohmic then it is most probably the cause of the high ideality factor.

If not, then it may be the high recombination rate at the interface between the the p and n-side. But if you produce your diode in a single crystal GaAs for example by doping it.

I believe that the M-S contacts is most probable to cause n greater than 2.

I would like that you go to the paper in the link:https://www.researchgate.net/publication/232710742_M_Abdelnaby_A_Zekry_F_Elakkad_and_H_F_Ragaie_Dependence_of_dark_current_on_zine_concentration_in_Znx_Cd1-x_SZn_Te_hetero_-_junctions_Solar_Energy_Materials_and_Solar_Cells_29_1993

you will find it useful for you.

Best wishes

Article M. Abdelnaby, A. Zekry, F. Elakkad and H. F. Ragaie, “ Depen...

 Dear Colleagues,

Welcome again.

I revisited this subject again because of the importance of the concepts introduced in the cited paper about the effect of the M-S contact on the performance of the advanced  solar cell structures. 

Before i give my comments on the subject, i would like to invite Siwei to report about any news concerning his relatively high ideality factor of his diodes. This may enrich the discussion.

One of the main conclusions of the investigations in the paper: Effect of MS contact.......,

is that the nonlinear MS contacts affects the i-v characteristics in a unique way such that The dark I-V characteristics has a larger voltage than the the corresponding solar cell with low ohmic M-S contact and the illuminated I-V curve has an S-shape with inflection around the zero current point which is the point of open circuit voltage. SO, THERE IS NO CROSSOVER OF THE DARK AND ILLUMINATED CURVES.

The other main point is that the presence of an additional ohmic series resistance with the nonlinear M-S contact causes may cause the reduction of the short circuit current to be less than the photocurrent.  To reach the photocurrent one has to reverse bias the solar cell . The I-V curve in the fourth quadrant will be an inclined straight line. Please inspect the i-v curves the mentioned paper.

The causes of the crossover between the dark and illuminated I-V curves of some peculiar solar cells was discussed in the link: https://www.researchgate.net/post/The_effect_of_interface_states_and_charges_on_the_performance_of_heterojunction_solar_cells_from_widegap_materials.

The last main effect is that the nonlinear M-S contact can cause an apparently higher ideality factor for the diode of the solar cell.

Of course one has to make the metal semiconductor contacts for electrically accessing the electronic devices low ohmic such that the voltage drop across them is negligible compared to the drop on the device junctions.

This is one of the important topics in the standard books of semiconductor devices.

Best wishes