The side chain effect on difluoro-substituted dibenzo[a,c]phenazine based conjugated polymers as donor materials for high efficiency polymer solar cells

Abstract

Two conjugated polymers with benzodithiophene derivatives as the donor unit and planar difluoro-substituted dibenzo[a,c]phenazine as the acceptor unit P1, P2-L and P2-H were designed, synthesized, and used as the donor material in polymer solar cells. P2-H exhibits the highest hole mobility of 1.54 × 10⁻² cm² V⁻¹ s⁻¹. Polymer solar cells (PSCs) with a blend of P1:PC₇₁BM (1 : 1.5, by weight) as the active layer show the highest power conversion efficiency (PCE) of 6.0% with an open circuit voltage (V_oc) of 0.74 V, a short circuit current (J_sc) of 12.50 mA cm⁻², and a fill factor (FF) of 0.65.