Benzo[1,2-b: 4,5-b′]dithiophene (BDT)-based small molecules for solution processed organic solar cells

Solution processed small molecule based solar cells have become a competitive alternative to their polymer counterparts due to the advantages of their defined structure and thus less batch to batch variation. With a large and rigid planar conjugated structure, the benzo[1,2-b:4,5-b '] dithiophene (BDT) unit has become one of the most widely used and studied building blocks for high performance small molecule based photovoltaic devices. In this review article, we review the progress made in the field of small molecules containing BDT units for solution-processed organic photovoltaic cells. Insights into several important aspects regarding the design and synthesis of BDT based small molecules are also included.