Monohalogenated Quinoxaline-Based Nonfullerene Acceptor to Modulate Photovoltaic Performance

Quinoxaline (Qx) is an important electron-deficient unit; however, the role played by the substituted halogen atoms on it has not been fully understood yet, although they have significantly promoted the performance of organic photovoltaics. Herein, we designed a wide-band-gap small molecule Cl-Qx3b, in which only one chloride atom was selectively substituted on the position of Qx near the central indaceno[2,1-b:6,5-b ']-dithiophene unit. Together with the other fluorinated analogue F-Qx3b previously reported by ourselves, we clarified the effect of halogen atoms on the photovoltaic property by choosing two polymers J52-Cl and J52-F as the donors, in which chlorine and fluorine atoms are substituted on the conjugated side chain. It was found that (1) chlorination shows lower nonradiative voltage loss and (2) fluorination exhibits suppressed charge carrier recombination. Our work gives a detailed explanation of the effect of monohalogenation on Qx on the photovoltaic property of Qx-based acceptors and thus an insight into heteroatom substitutions on Qx especially in both donor and acceptor.

Automated summary

This study designed a wide-band-gap small molecule Cl-Qx3b and clarified the effect of halogen atoms on the photovoltaic property. Chlorination was found to show lower nonradiative voltage loss, while fluorination exhibited suppressed charge carrier recombination.