An insulating layer must have pin-hole free nature. All the oxides (e.g. Al2O3, HfO2 etc grown by ALD) has enormous amount of pin-hole that effects the transport behavior of solar cell. So a flat, pin-hole free insulating layer like h-BN that has strong breakdown strength could facilitate solar cell efficiency.
Dear Imtisal,
would you please specify the solar cell type to give specific answer on this question. However there are some rules which govern the selection of the interfacial layer:
It must passivate the surface of the active absorbing layer to reduce the surface recombination velocity. So, it must saturate all the chemical bonds at the surface.
- The second property is that it must have energy band structure to facilitate the transport of one type of charges here electrons in your oxide material from the active region to the cathode. It is so that one selects the material such that its conduction band edge lies slightly under that of the active material such that the electrons can slide easily down to the interfacial layer and then to the cathode metal. This will help also to avoid loss in the open circuit voltage because of the energy level mismatch between in case of direct contacting the active layer and the cathode.
The interfacial layer on the other side must make an ohmic contact with the metal of the cathode.
- Other major requirement is high transport efficiency with small thickness and high conductivity
- If it is in the path of the incident solar radiation to the active material , it must be optically transparent with the highest optical transmission coefficient
Best wishes
Dear Imtisal
I agree with Dr. Abdelhalim answer, also mismatch between layers is very important, therefore, all the oxides does not play the similar role (depending on their lattice constants which can give a good result).
With best my wishes
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