Fluorinated benzothiadiazole-based small molecules for photovoltaic applications

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>A series of medium band gap conjugated small molecules with a typical D-π-A-π-D structure, in which triphenylamine, thiophene, and benzothiadiazole are used as an electron-donor, a bridge, and an electron-acceptor, respectively, have been synthesized. To investigate the effects of strong electron-withdrawing fluorine atoms on various properties, one and two fluorine substituents are introduced to the central benzothiadiazole unit of N-(4-(5-(7-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)phenyl)-N-phenylbenzenamine (<B>TPA-TBT</B>) to give <B>TPA-TBT-1F</B> and <B>TPA-TBT-2F</B>, respectively. Owing to the significant contributions of fluorine atoms, these small molecules exhibit clearly distinctive optical and electrochemical properties. Inverted-type organic photovoltaic cells (OPVs) with a configuration of ITO/ZnO/small molecules: PC<SUB>71</SUB>BM/MoO<SUB>3</SUB>/Al were fabricated and the fabricated cells showed maximum power conversion efficiencies of 0.84, 1.15 and 1.70% for <B>TPA-TBT</B>, <B>TPA-TBT-1F</B> and <B>TPA-TBT-2F</B>, respectively. The superior photovoltaic performance of <B>TPA-TBT-2F</B> is attributed to the relatively deep energy level of highest occupied molecular orbital (HOMO) and to more balanced electron- and hole-mobility within photoconversion layer. Therefore, this study can provide insights into the tuning the properties of benzothiadiazole-based small molecules by introducing fluorine substituents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A series of medium band gap conjugated small molecules have been synthesized. </LI> <LI> Selective incorporation of fluorine atoms on the benzothiadiazole acceptors. </LI> <LI> Optical, electrochemical and photovoltaic properties have been investigated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>