All-Polymer Solar Cell with High Near-Infrared Response Based on a Naphthodithiophene Diimide (NDTI) Copolymer.

Polymer-blend solar cells (all-PSCs) based on a copolymer of naphthodithiophene diimide and bithiophene (PNDTI-BT-DT) as a near-infrared absorber as well as an electron acceptor were fabricated in combination with PTB7 as an electron donor. Notably, the external quantum efficiency spectra of the all-PSCs demonstrated photoresponse up to 900 nm with the efficiency of 25% at 800 nm, which is much higher than that for the previously reported all-PSCs. Power conversion efficiency as high as 2.59% was achieved under the irradiation of simulated solar light (AM1.5, 100 mW/cm). Both PNDTI-BT-DT and PTB7 formed a crystalline structure in the blend films similar to in the pristine films, leading to the efficient charge generation contributed from both polymers.