The Role of Terminal Fluorination on Energy Inversion in Organic Solar Cells.

ABSTRACT

Suppressing the non-radiative energy loss (ΔE3) mediated by triplet charge transfer state is crucial for high-performance organic solar cells (OSCs). Here, we decode the energy inversion through multi-scale theoretical simulation, which inhibits the non-emissive triplet (T1) state formation. However, it is mystified by the system dependence. We first demonstrate a direct relationship of "the probability of Face-on orientation (PFace-on) is proportional to the probability of energy inversion (PEI)", which is related to the function of terminal fluorination. Through Pearson's correlation coefficient and machine learning model, the useful stacking structural parameters were obtained to clarify the effect of π-bridge group on the function of terminal fluorination. Based on the molecular descriptors established, we explain that the fluorination effect is beneficial to Face-on orientation and thus energy inversion due to the enhanced intermolecular coupling. But the π-bridge inhibits this coupling with the interfacial stacking configuration appearing more "TT_IC". This work provides a directional standard for promoting energy inversion to reduce ΔE3 for the high-performance OSCs.