Novel isoindigo-based conjugated polymers for solar cells and field effect transistors

Abstract

Three new isoindigo containing donor–acceptor (D–A) type conjugated polymers were synthesized by palladium catalyzed Suzuki polycondensation and used as donor materials for polymer solar cells (PSCs) and field effect transistors (FETs). All the polymers possess good solubility in common organic solvents, high thermal stability, and broad absorption in the range of 300 to 750 nm. These polymers have narrow band gaps (1.66 to 1.70 eV) and low lying HOMO energy levels (5.15 to 5.31 eV). Hole mobilities of these polymers are in the range of 1.78 × 10⁻³ to 2.62 × 10⁻³ cm² V⁻¹ s⁻¹. PSCs based on P3:PC₇₁BM (1 : 2, by weight) gave the best device performance with a power conversion efficiency (PCE) of 1.75%, a short-circuit current density (J_sc) of 4.74 mA cm⁻², an open-circuit voltage (V_oc) of 0.81 V, and a fill factor (FF) of 0.45, indicating these polymers can be promising donor polymers for polymer solar cells.