The contact between the n-type interlayer and the donor provides an extra interface for charge dissociation.

High-performance bulk-heterojunction (BHJ) polymer solar cells (PSCs) processed from non-halogenated solvents with power conversion efficiency values over 7% are demonstrated for the first time. The effects of these solvents on the morphology, charge mobility, and PSC device performance have been systematically studied. The general applicability of these non-halogenated solvents to diverse polymer/fullerene systems has also been demonstrated.