What are the forces that controls the dissociation process. Why at hetero-junction, dissociation takes place. Please give me some analytical and quantitative idea about this process. Is there any relation between band-gap discontinuity and dissociation probability (dissociation rate)?
Hi,
You can see the following link, which describes the mechanism and rate of exciton dissociation at the donor-acceptor interface in bulk-heterojunction organic solar cells
https://www.researchgate.net/publication/257976017_Study_of_the_mechanism_and_rate_of_exciton_dissociation_at_the_donor-acceptor_interface_in_bulk-heterojunction_organic_solar_cells
The sharp increase in the exciton dissociation efficiency at the hetero-junction is due to the discontinuous HOMO and LUMO levels at the donor-acceptor interface which can efficiently separate the bound electron-hole pairs into free charge carriers. The energy level offset for the HOMO or LUMO should be larger than the exciton binding energy. The minimum energy E needed to overcome the Coulomb electric force is given by the energy difference between the transport gap and optical gap of organic material. For most organic materials E is within 0.2-2 eV.
HOMO and LUMO are acronyms for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively.
Hope this information will be helpful for you.
Article Study of the mechanism and rate of exciton dissociation at t...
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