Dear Loic,

I will try to introduce my understanding to your question. You ask if the ration of donor molecules to the acceptor molecules is 1 to 1 what is the percentage of the pairs that can affect a transfer from their donors to their acceptors.

My answer is if they are in intimate contact with each other the elections in the donor will be captured by the acceptors. and the effective capturing ratio will be about 100 percent. I think the problem arises when clusters are formed. In this case the donor molecules will not be directly contacted with an acceptor molecule and the transfer efficiency may not equal to one. Therefore how the mixing is affected inside the bulk heterojunction between the the donors and acceptors is important.

My opinion is based on physical and logical reasoning.

I think whenever the distance between the acceptor molecules and the donor molecules is smaller than the diffusion length of the excitons the electrons will be captured by the acceptors. This issue is foun Conference Paper Generic Analytical Models for Organic and Perovskite Solar Cells

I would like that you have a look at my paper:

Best wishes

Thank you for this answer Pr. Zekry. I've added an image to improve the clarity of my question (I apologize for my english!). I was more looking for experimental data. I know that TEM tomorgraphy has made possible the access to the precise 3D morphology of a BHJ and was wondering if anybody had ever used this technic to calculate the precise ratio of (donor-acceptor charge transfer complexes):(pure donor + pure acceptor). In other words what is the % of molecules being at an interface (bright green circles in the uploaded image) compared to all other molecules that don't have any contact with the interface (black circles + light green lines)?

What does this have to do with the question?