Subharsi,

Ferroelectric materials becomes polarized when when their ferroelectric domains are oriented by an external electric field. So one side of the a sheet of ferroelectric material will be positively charged and the otherside will be negatively charged. These charges produce an electric field inside the material similar to the built in electric field because of the junction formation in the normal pn junction solar cells. So, the cell is just a very thin slap sandwiched between two metallic electrodes.

When illuminated electron hole pairs will be generated and they will be separated by the built in electric field where the electrons will flow towards the positively charged electrode and the holes will move to the negatively charged electrode.

If one puts a load a current will flow this load which proves the photovoltaic effects: Article Ferroelectric solar cells based on inorganic–organic hybrid perovskite

Best wishes

Subharsi,

Ferroelectric materials becomes polarized when when their ferroelectric domains are oriented by an external electric field. So one side of the a sheet of ferroelectric material will be positively charged and the otherside will be negatively charged. These charges produce an electric field inside the material similar to the built in electric field because of the junction formation in the normal pn junction solar cells. So, the cell is just a very thin slap sandwiched between two metallic electrodes.

When illuminated electron hole pairs will be generated and they will be separated by the built in electric field where the electrons will flow towards the positively charged electrode and the holes will move to the negatively charged electrode.

If one puts a load a current will flow this load which proves the photovoltaic effects: Article Ferroelectric solar cells based on inorganic–organic hybrid perovskite

Best wishes

In case of ferroelctric photovoltaic , the shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a sub picosecond timescale. The currents originate when the excited electrons transfer between different bands or scatter inside these bands, and asymmetrically shift their centres of mass in elementary cells.

Read some articles related to shift current in ferrolectric materials.

Abdelhalim abdelnaby Zekry

Actually i understand the polarization concept across the ferroelectric domains with the application of any external field but with respect to your answer do the dipoles breaks and charges separated ?

@ Chandra Bhal Singh please if you don't mind kindly share some articles or their links.

I am agree to Subhasri that important point what I also want to know how this current flow because all the positive and negative charges here are restricted to two poles so where from the additional electrons come to flow and produce current? This is important question in case of FERROELECTRIC no matter either polarized or not.. if we call the defects are responsible then I think the ferroelectricity will be disturb and will decrease. So considering the opportunity to use built-in electric field of ferroelectrics we must have to think about where from the charges will come for current? So please explain in details with some good references.

Thank you.

Jafar Hussain Shah This link will help you

Article Quantum kinetic theory of shift current electron pumping in ...

Dear Subharsi,

welcome again,

You agree that there is a built in electric field because of the polarization of the ferroelectric slab.

The ferroelectric material has the ability to conduct electricity by drifting the mobile electrons in the conduction band and holes in the valence band of the material. The mobility could be small but not zero. To assist the electrons and holes to be dispatched rapidly by the built in electric field one makes the thickness of the slab very small. This is one of the tricks to make this device works better.

Know assume that light strikes the material, electrons hole pairs will be generated and then separated by the electric field where the holes are made to drift to the negatively charged electrode and the electrons drift to the positively charged electrodes.. If one put a load between the electrodes a current will flow through the load proving the the photovoltaic effect.

Best wishes

But my question is still there dear Prof. I mean for ferroelectric materials we believe that these are bipolar material or they have dipoles. When we consider dipoles I think then positive and negative charges should be at opposite ends. Now main point is here what I want to get clear that are the free charges are not part of dipoles and available to move or these charges get separate from dipoles? If there are no free charges and electron hole pair get separate from bound charges then definitely we need a large intensity of light which could overcome this internal electric field. So what I want to know is that where from come the electron and hole in ferroelectric for current generation? @ Abdelhalim zekry

Jafar Hussain Shah Yes my question resembles with your statement..

Abdelhalim abdelnaby Zekry Hello Sir, w.r.t your answer ferroelectric polarization drifts the mobile electrons then i am confused about the fact that these mobile electrons arise from where free or bound ?

Dear Subhasri,

welcome again,

These are free electrons and holes. Only that can drift in the electric field is the free electrons and holes. When photons with sufficient energy is illuminating the ferroelectric material they will generate electrons hole pairs with the electrons are transferred from the valence band to the conduction band while the holes will rfemain on the top of the valence band. This process is called photo generation of electron hole pairs. I would like that you read my book chapter solar cells and arrays in Elsevier: Chapter Solar cells and arrays: Principles, analysis and design

After reading it please give a comment on it. Thank tout.

Best wishes

Please look at the work by

Sun group

at

Northeastern University

at

Boston, MA

USA

Abdelhalim abdelnaby Zekry

Thank you for your answer. Generally in multiferroics majority electrons are bound and only few electrons are free in the form of defects or vacancies. That means according to your answer these few electrons are responsible for Photovoltaic Effect.