Importantly, three batches of
PNTB6-Cl with varying molecular weights (Mn: 45.27-91.53 KDa) exhibited
PCE deviation smaller than 4 %. It was further revealed that the
chloroform processing dissolved the PNTB-Cl in both amorphous and
crystalline regions, however, it only partially washed away amorphous
PNTB6-Cl which bring forth the advantage of reducing the traps in LBL
films that benefits the FF value, facilitating electron acceptor
penetration. This study suggests the importance of controlling
solubility properties of polymer donors toward high-performance
LBL-OSCs. The use of different additives to control the donor and
acceptor layers separately is a promising approach to achieve high
efficiency of LbL-OSCs. Zhang et al. [67]prepared PNTB6-Cl:Y6-based LbL-OSCs by adding DPE and DFB solvent
additives into PNTB6-Cl chlorobenzene solution and Y6 chloroform
solution separately. It improves the photogenerated exciton
distribution, charge transport and collection, resulting in PCE of 17.53
% that is much higher than 16.38 % for controlled devices. Using the
same processing approach, they fabricated PNTB6-Cl: BTP-4F-12-based
LbL-OSCs and achieved a PCE of 17.81 % by using DPE and DIO to optimize
donor and acceptor layers separately.[68] Shaoet al. [71] reported a self-powered organic
photodetector (OPD) based on PNTB6-Cl:Y6 blend active film. The
PNTB6-Cl:Y6 blend film exhibited a remarkable intrinsic stretchability
up to 100 % strain. The OPD not only exhibited impressive weak-light
detection ability, but also had a high anisotropic response rate of 1.42
under parallel and transversely polarized light irradiation.