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 stateis crucial for high-performance organic solar cells (OSCs). Here, we decode the energy inversionthroughmulti-scale theoretical simulation, which inhibits the non-emissivetriplet (T1) state formation. However, itis 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 coefficientand machine learning model, the useful stacking structural parameters were obtained to clarify the effect of π-bridge group on the function of terminal fluorination. Basedon the molecular descriptorsestablished,we explain that the fluorination effect is beneficial to Face-onorientationand thus energy inversiondue tothe enhancedintermolecular coupling.Butthe π-bridge inhibits thiscoupling with the interfacialstacking configuration appearingmore "TT_IC".This work provides a directional standard for promotingenergy inversionto reduceΔE3for the high-performance OSCs.