The enhanced photovoltaic performance of fluorinated acenaphtho[1,2-b]quinoxaline based low band gap polymer

- Poly(fluorinated acenaphthoquinoxaline-co-benzodithiophene) was synthesized and PCE of 4.72% was obtained for solar cells.
- Polymer solar cells with the blend of P1 and PC71BM as the active layer showed a PCE of 4.72%.
- P1 based devices have the highest PCE report for acenaphtho[1,2-b]quinoxaline based polymer solar cells.

A new low band gap polymer P1 with fluorinated acenaphtho[1,2-b]quinoxaline (AQ) as the acceptor unit and benzo[1,2-b:4,5-b′]dithiophene as the donor unit has been designed and synthesized. Comparing with its non-fluorinated analog polymer P2, P1 shows a lower band gap of 1.76 eV with a deeper HOMO energy level of −5.54 eV. Polymer solar cells with the blend of P1 and PC71BM as the active layer without the additive or annealing showed a PCE of 4.72%, which was higher than P2 based devices with a PCE of 1.65%. Obviously, P1 can endow devices with a Voc of 0.77 V and a Jsc of 10.75 mA cm−2, which are higher than that of P2 based devices with a Voc of 0.75 V and a Jsc of 4.41 mA cm−2, such an enhanced photovoltaic performance can be attributed to the broader absorption, the improvement of film morphology, and the higher charge mobility. Thus, fluorinated AQ can be a useful acceptor unit to construct narrow band gap conjugated polymers. To the best of our knowledge, this is the highest PCE report for AQ based polymer solar cells.

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