Synthesis of diketopyrrolopyrrole (DPP)-based small molecule donors containing thiophene or furan for photovoltaic applications

• Two small molecules based on diketopyrrolopyrrole were synthesized for OPVs.
• To determine the effects of furan and thiophene on the performance.
• DPP4T yielded a better PCE (1.44%) than DPP2F2T (0.85%).
• DPP4T have the broad absorption and the low-lying HOMO energy level than DPP2F2T.

Two π-conjugated small molecules based on diketopyrrolopyrrole (DPP), DPP4T and DPP2F2T, were synthesized using the Suzuki coupling reaction. DPP4T and DPP2F2T contained furan and thiophene, respectively, next to a DPP core. Organic photovoltaic cells (OPVs) were fabricated using two DPP-based oligothiophenes as donors. DPP4T showed higher power conversion efficiency (PCE) (1.44%) than DPP2F2T (0.85%). The short-circuit current (JSC) of DPP4T (4.38 mA cm−2) was nearly twice that of DPP2F2T (2.49 mA cm−2). The improved photovoltaic properties of DPP4T could be explained by the optical properties and the film morphology.

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