Donor-acceptor small molecule with coplanar and rigid π-bridge for efficient organic solar cells

A novel donor–acceptor (D–A) donor molecule, 1, comprising of two di-p-tolylamino donors and a dicyanovinylene acceptor bridged by a planar and rigid fluorene moiety has been synthesized and characterized. The molecular structure and crystal packing of 1 was characterized by single-crystal X-ray crystallography. Such molecular configuration endowed 1 with an efficient D–A interaction, rendering an intense ICT absorption band for efficiently light-harvesting and retain low-lying HOMO for generating sufficient open-circuit voltage (Voc). The vacuum-deposited hybrid planar-mixed heterojunction (PMHJ) photovoltaic devices utilizing 1 as donor and C70 as acceptor to achieve power conversion efficiencies (PCEs) of 4.04 and 5.31% for the single- and tandem-cell photovoltaic devices under simulated AM 1.5 illumination (100 mW cm−2).