Donor-acceptor conjugated cooligomers for single molecule solar cells

Five novel donor-acceptor (D-A) conjugated cooligomers (F4B-hP, F5B-hP, F5B2[1,2]-hP, F5B2[1,3]-hP and F7B2[1,2]-hP) were synthesized. The absorption spectra of the cooligomers cover a wide range from 300 nm to 630 nm. The cooligomers could form films featured by alternating D-A lamellar nanostructures with the periods relative to the molecular lengths after thermal annealing or solvent vapor annealing. Single molecule solar cells were fabricated, and F5B-hP exhibited the best device performance. When the film of F5B-hP was thermally annealed, a power conversion efficiency (PCE) of 1.56% was realized. With solvent vapor annealing, the PCE could be further improved to 1.72% with a short-circuit current (J _SC) of 5.76 mA/cm², an open-circuit voltage (V _OC) of 0.87 V and a fill factor (FF) of 0.34.