Rational molecular design towards NIR absorption: efficient diketopyrrolopyrrole derivatives for organic solar cells and photothermal therapy

After the development of diketopyrrolopyrrole (DPP) in 1974, its derivatives have been widely explored for optoelectronic applications. In this review we discuss various donor/acceptor functionalized DPPs which have been recently published and systematically compare their properties. The modification of donor functionalized DPPs to tetracyanobutadiene (TCBD) bridged derivatives with improved acceptor strength and absorption in the near infra-red region has shown some exciting advancement in non-fullerene acceptors for organic solar cells and therapeutic agents in photothermal therapy and these are also described. The optoelectronic properties in relation to structural changes such as changes of the end capping groups, donor-acceptor moieties, aromatic moiety in the DPP core and number of DPP units in the molecular structure are discussed. We are expecting that the current review will provide guidelines for the exploration of new DPP based efficient materials for photovoltaic and biomedical applications. The present review focus on the progress and development of NIR absorbing small molecules based on diketopyrrolopyrrole for organic solar cells and photothermal therapy.