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 %.