Synthesis and photovoltaic properties of an n-type two-dimension-conjugated polymer based on perylene diimide and benzodithiophene with thiophene conjugated side chains

Abstract

A novel n-type two-dimensional (2D) conjugated polymer based on bithienyl-benzodithiophene (BDT) and perylene diimide (PDI), P(PDI-BDT-T), was synthesized by Stille coupling for application as an acceptor material in all-polymer solar cells (all-PSCs). P(PDI-BDT-T) exhibits broad absorption in the visible region with an optical bandgap (E_g) of 1.64 eV, and a LUMO level of −3.89 eV, which is similar to and slightly higher than that of PCBM, indicating that the polymer is a suitable acceptor to replace PCBM in PSCs. PSCs with P(PDI-BDT-T) as the acceptor and PTB7-Th as the donor demonstrated a power conversion efficiency (PCE) of 4.71% with a J_sc of 11.51 mA cm⁻², V_oc of 0.80 V, and FF of 51.1%. Meanwhile, the PCE of the PSCs based on the acceptor of a corresponding 1D-conjugated polymer P(PDI-BDT-O) with an alkoxy side chain on the BDT unit was only 2.75% with a J_sc of 10.14 mA cm⁻², V_oc of 0.72 V, and FF of 37.6%. These results indicate that the 2D-conjugated P(PDI-BDT-T) is a promising acceptor material for all-PSCs.