A carbon-oxygen-bridged ladder-type building block for efficient donor and acceptor materials used in organic solar cells

A carbon-oxygen-bridged ladder-type donor unit （CO5） was invented and prepared via an ＂intramolecu- lar demethanolization cyclization＂ approach. Its single crystal structure indicates enhanced planarity compared with the carbon-bridged analogue indacenodithiophene （IDT）. Owing to the stronger electron-donating capability of CO5 than IDT, CO5-based donor and acceptor materials show narrower bandgaps. A donor-acceptor （D-A） copolymer donor （PCO5TPD） and an A-D-A nonfullerene acceptor （COSIC） demonstrated higher performance than IDT-based counterparts, PIDTTPD and IDTIC, respec-tively. The better performance of CO5-based materials results from their stronger light-harvesting capability and higher charge-carrier mobilities.