D–A copolymers containing lactam moieties for polymer solar cells

Abstract

Two D–A copolymers P1 and P2 were developed by copolymerizing a new lactam acceptor unit, [7,7′-bidithieno[3,2-b:2′,3′-d]pyridine]-5,5′(4H,4′H)-dione (BDTP), with benzo[1,2-b:4,5-b′]dithiophene (BDT) or selenophene. The copolymers have good solubility, thermal stability and deep HOMO levels. P2:PC₇₁BM solar cells gave a PCE of 6.76%, with a V_oc of 0.91 V, a J_sc of 9.96 mA cm⁻² and an outstanding FF of 74.5%.