If one contacts two materials with different work function an interface dipole layer will be built between the two materials. Associated with this dipole layer is the built in electric field and the built in potential difference. The built in potential difference under equilibrium is called the contact difference of potential and it is equal to the difference in the work functions of the two materials. Such contact difference of potential constitutes a potential barrier to stop the flow of majority carrier from their original side to the other side.

The potential barrier between the two materials can be changed by the applied voltage. If the junction is forward biased the barrier height will be lowered and if it is reverse biased the barrier height will increase.

You question is a very fundamental question relating the principle operation of the junctions if they are homojunction or heterojunctions.

So, you have to precise the definitions of the basic quantities for such junctions.

The pn junction theory is the basis for understanding the more complicated electron devices.

I would like to advice you fo follow the book: Book Electronic Devices

As for the organic solar cells contact difference of potential please refer to the paper: Conference Paper Generic Analytical Models for Organic and Perovskite Solar Cells

Best wishes

Nolasco, J. C., Antonio Sánchez-Díaz, R. Cabré, J. Ferré-Borrull, L. F. Marsal, E. Palomares, and J. Pallarès. "Relation between the barrier interface and the built-in potential in pentacene/C 60 solar cell." Applied Physics Letters 97, no. 1 (2010): 134.

Thanks @Azeez

Dear Anand Pandey

I'm attaching a reference from a book in Semiconductor Physics, this book is very basic but it has some information I think it can help.

Book Fundamentals of Electronic Devices & Circuits (from A to Z)

Thank you @Hichem

You are welcome @ Anand

If one contacts two materials with different work function an interface dipole layer will be built between the two materials. Associated with this dipole layer is the built in electric field and the built in potential difference. The built in potential difference under equilibrium is called the contact difference of potential and it is equal to the difference in the work functions of the two materials. Such contact difference of potential constitutes a potential barrier to stop the flow of majority carrier from their original side to the other side.

The potential barrier between the two materials can be changed by the applied voltage. If the junction is forward biased the barrier height will be lowered and if it is reverse biased the barrier height will increase.

You question is a very fundamental question relating the principle operation of the junctions if they are homojunction or heterojunctions.

So, you have to precise the definitions of the basic quantities for such junctions.

The pn junction theory is the basis for understanding the more complicated electron devices.

I would like to advice you fo follow the book: Book Electronic Devices

As for the organic solar cells contact difference of potential please refer to the paper: Conference Paper Generic Analytical Models for Organic and Perovskite Solar Cells

Best wishes

https://aip.scitation.org/doi/abs/10.1063/1.3456393?journalCode=apl

Thanks @Zekry sir.

How charge transport mchanism affects when Built in potetial is low or high ?

Value of barrier height and built in potential usually varies for metal semiconductor junction under equillibrium. Barrier height is calculated fron the fermi level of metal in metal side but for semiconductor side it is measured from conduction band edge.