Pyran-Bridged Indacenodithiophene as a Building Block for Constructing Efficient A-D-A-Type Nonfullerene Acceptors for Polymer Solar Cells.

In recent years, nonfullerene acceptors have attracted much attention, owing to their great potential for use in high-performance polymer solar cells.The ladder-type building block, pyran-bridged indacenodithiophene (PDT), was used for constructing A-D-A nonfullerene acceptors through introduction of oxygen atoms into an indacenodithiophene (IDT) unit. The synthesis of PDT is accomplished by a BBr3 -mediated tandem cyclization-deprotection reaction to construct the pyran ring. Hence, molecular acceptor PTIC was synthesized and used in a polymer solar cell device. Compared to the IDT-based acceptor, PTIC exhibits higher HOMO levels and wider optical band gap at 550-800 nm. Devices fabricated with poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)-benzo[1,2-c:4,5-c']dithiophene-4,8-dione)] (PBDB-T):PTIC as the active layer give a power conversion efficiency (PCE) of 7.66 %.