The charge dynamics of PBDB-TF:IT-4F based non-fullerene organic solar cells with 1,8-diiodooctane additive

Abstract

For most of the PBDB-TF:IT-4F based non-fullerene organic solar cells (OSCs), 1,8-diiodooctane (DIO) is introduced to improve the performance of the OSCs. However, the charge dynamics of DIO addition on device performance improvement is still not clear. The relationship between DIO and charge dynamics, as well as the morphology of active layer are synthetically investigated in this work. Experimental study indicates that the DIO addition could reduce domain size which is beneficial to exciton dissociation, but it also make more PBDB-TF migrate to the top surface of active layer and increase trap-assisted recombination which sacrifice the bi-continuous charge transfer channels in the PBDB-TF:IT-4F film. These findings may provide new ideas for improving the performance of OSCs by adjusting the structure of OSCs or regulating the vertical distribution of the donor and acceptor materials.