Donor/Acceptor Interface Modifications in Organic Solar Cells

摘要

Low dielectric constant of organic semiconductor materials gives rise to the high binding energy for photoinduced excitons, typically one order of magnitude higher than the thermal energy at room temperature [1]. This results in the relatively poor performance of organic solar cells (OSCs). A p-n junction interface is therefore utilized as the driving force for charge separation relying on energy offsets between the lowest unoccupied molecular orbitals (LUMO) or highest occupied molecular orbitals (HOMO) from the corresponding p-type (donor (D)) and n-type (acceptor (A)) materials [2]. Meanwhile charge recombination, which is viewed as the major loss in OSCs, also takes place at this D/A interface. In addition, the energy difference between HOMO of D and LUMO of A (E_(DA)) was found to be closely related to the open circuit voltage (V_(OC)) of OSCs [3]. These key roles entitle the D/A interface to the most important interface to control in OSCs [4].